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Silicon, a ubiquitous material in modern computing, is an emerging platform for realizing a source of indistinguishable single-photons on demand. The integration of recently discovered single-photon emitters in silicon into photonic structures is advantageous to exploit their full potential for integrated photonic quantum technologies. Here, we show the integration of an ensemble of telecom photon emitters in a two-dimensional array of silicon nanopillars. We developed a top-down nanofabrication method, enabling the production of thousands of individual nanopillars per square millimeter with state-of-the-art photonic-circuit pitch, all the while being free of fabrication-related radiation damage defects. We found a waveguiding effect of the 1278 nm G-center emission along individual pillars accompanied by improved brightness, compared to that of bulk silicon. These results open pathways to monolithically integrating single-photon emitters into a photonic platform.

We report the use of optically addressable spin qubits in SiC to probe the magnetic stray fields generated by a ferromagnetic microstructure lithographically patterned on the surface of a SiC crystal. The stray fields cause shifts in the resonance frequency of the spin centers. The spin resonance is driven by a micrometer-sized microwave antenna patterned adjacent to the magnetic element. The patterning of the antenna is done to ensure that the driving microwave fields are delivered locally and more efficiently compared to conventional, millimeter-sized circuits. A clear difference in the resonance frequency of the spin centers in SiC is observed at various distances to the magnetic element, for two different magnetic states. Our results offer a wafer-scale platform to develop hybrid magnon-quantum applications by deploying local microwave fields and the stray field landscape at the micrometer lengthscale., Comment: 4 pages, 4 figures, submitted to APL

Ge with a quasi-direct band gap can be realized by strain engineering, alloying with Sn, or ultrahigh n-type doping. In this work, we use all three approaches together to fabricate direct-band-gap Ge-Sn alloys. The heavily doped n-type Ge-Sn is realized with CMOS-compatible nonequilibrium material processing. P is used to form highly doped n-type Ge-Sn layers and to modify the lattice parameter of P-doped Ge-Sn alloys. The strain engineering in heavily-P-doped Ge-Sn films is confirmed by x-ray diffraction and micro Raman spectroscopy. The change of the band gap in P-doped Ge-Sn alloy as a function of P concentration is theoretically predicted by density functional theory and experimentally verified by near-infrared spectroscopic ellipsometry. According to the shift of the absorption edge, it is shown that for an electron concentration greater than 1x10^20 cm-3 the band-gap renormalization is partially compensated by the Burstein-Moss effect. These results indicate that Ge-based materials have high potential for use in near-infrared optoelectronic devices, fully compatible with CMOS technology., 20 pages, 6 figures

Crystalline β-Ga2O3 thin films on (100)- and (111)-oriented Si substrates are produced by pulsed laser deposition. The as-deposited thin films are demonstrated to be polycrystalline and contain a slight deficit of oxygen atoms as measured by x-ray diffraction spectroscopy and Rutherford backscattering spectrometry, respectively. The crystallographic orientation of the Si substrate is found to play no role on the ultimate properties of the films. A direct optical band gap of 4.8 eV is determined by temperature-dependent photoluminescence excitation (PLE). Temperature-dependent PLE spectra reveal the existence of a deep acceptor level of around 1.1 eV with respect to the valence band related to self-trapped holes. We experimentally demonstrate that point defects in O-poor β-Ga2O3 thin films act as deep donors and the optical transitions are found to take place via recombination of electrons from one of the intrinsic deep donor levels with self-trapped holes located at 1.1 eV above the valence band. The 3.17 eV ultraviolet photoluminescence is proven to be related to self-trapped holes in a small polaron state between two O(II)-s sites, whereas the two blue (2.98, 2.72 eV) and the green (2.39 eV) luminescence bands are mainly originated from gallium-oxygen vacancy pairs in the (1-) charge state, gallium vacancies in the (2-) charge state and neutral oxygen interstitials, respectively.

The n-type doping of Ge is self-limiting process due to formation of the vacancy-donor complexes (Dn V with n≤4). Here we report on experiments and density functional theory (DFT) calculations solving the basic problem of donor deactivation in heavily doped Ge. The self-healing process of heavily doped n-type Ge is achieved by rear-side flash lamp annealing (r-FLA) for 20 ms with the peak temperature of about 1050 K. The positron-annihilation lifetime spectroscopy (PALS) reveals that the P4V clusters are main defects in the as-grown Ge:P samples. Millisecond range high-temperature treatment dissociates the phosphorus-vacancy cluster (P4V) and, as shown by SIMS, fully supress the P diffusion. The electrochemical capacitance-voltage (ECV) profiling shows that the effective carrier concentration in P doped Ge (P concentration - 1×1020 cm-3) increases from about 3×1019 cm-3 in as-grown sample to above 8×1019 cm-3 after r-FLA. For the first time using structural (PALS, SIMS) and electrical (ECV) characterization combined with DFT calculations we were able to addressed, explained and solved the fundamental problem hindering the full integration of Ge with CMOS technology.

A method for cross-sectional doping of individual Si/SiO2 core/shell nanowires (NWs) is presented. P and B atoms are laterally implanted at different depths in the Si core. The healing of the implantation-related damage together with the electrical activation of the dopants takes place via solid phase epitaxy driven by millisecond-range flash lamp annealing. Electrical measurements through a bevel formed along the NW enabled us to demonstrate the concurrent formation of n- and p-type regions in individual Si/SiO2 core/shell NWs. These results might pave the way for ion beam doping of nanostructured semiconductors produced by using either top-down or bottom-up approaches.

The intentional introduction of deep-level dopants into a semiconductor in excess of equilibrium concentrations causes a broadening of dopant energy levels into an intermediate band between the valence and conduction bands.[1,2] This phenomenon is referred to as hyperdoping. As intermediate-band material, bulk Si hyperdoped with chalcogens or transition metals holds promises for Si-based short-wavelength infrared photodetectors and solar cells.[3,4] Intermediate-band nanowires could potentially be used instead of bulk materials to overcome the Shockley-Queisser limit and to improve efficiency in solar cells.[5,6] Here, we show a CMOS-compatible method based on non-equilibrium processing for the controlled doping of Si at the nanoscale with dopant concentrations several orders of magnitude above the equilibrium solid solubility. The approach relies on using ion implantation followed by flash lamp annealing for hyperdoping Si/SiO2 core/shell nanowires. We induce, by millisecond-flash lamp annealing, a bottom-up template-assisted solid-phase epitaxy recrystallization of the nanowires. This results in the formation of intermediate-band Se-hyperdoped nanowires which exhibit room-temperature sub-band gap optoelectronic photoresponse when configured as a photoconductor device. References [1] Sher M J, Mazur E, Appl. Phys. Lett. 2014;105:032103. [2] Ertekin E, Winkler M, T, Recht D, Said A J, Aziz M J, Buonassisi T, Grossman J C, Phys. Rev. Lett. 2012;108:026401. [3] Berencén Y, Prucnal S, Liu F, Skorupa I, Hübner R, Rebohle L, Zhou S, Schneider H, Helm M, Skorupa W, Sci. Rep. 2017;7:43688. [4] Mailoa J P, Akey A J, Simmons C B, Hutchinson D, Mathews J, Sullivan J T, Recht D, Winkler M T, Williams J S, Warrender J M, Persans P D, Aziz M J, Buonassisi T, Nat. Commun. 2014;5:3011. [5] Beard M C, Luther J M, Nozik A J, Nat. Nanotech. 2014;9:951. [6] Tian B, Zheng X, Kempa T J, Fang Y, Yu N, Yu G, Huang J, Lieber C M, Nature 2007:449;885.

Hyperdoping consists of the intentional introduction of deep‐level dopants into a semiconductor in excess of equilibrium concentrations. This causes a broadening of dopant energy levels into an intermediate band between the valence and the conduction bands. Recently, bulk Si hyperdoped with chalcogens or transition metals is demonstrated to be an appropriate intermediate‐band material for Si‐based short‐wavelength infrared photodetectors. Intermediate‐band nanowires can potentially be used instead of bulk materials to overcome the Shockley–Queisser limit and to improve efficiency in solar cells, but fundamental scientific questions in hyperdoping Si nanowires require experimental verification. The development of a method for obtaining controlled hyperdoping levels at the nanoscale concomitant with the electrical activation of dopants is, therefore, vital to understanding these issues. Here, this paper shows a complementary metal‐oxide‐semiconductor (CMOS)‐compatible technique based on nonequilibrium processing for the controlled doping of Si at the nanoscale with dopant concentrations several orders of magnitude greater than the equilibrium solid solubility. Through the nanoscale spatially controlled implantation of dopants, and a bottom‐up template‐assisted solid phase recrystallization of the nanowires with the use of millisecond‐flash lamp annealing, Se‐hyperdoped Si/SiO2 core/shell nanowires are formed that have a room‐temperature sub‐bandgap optoelectronic photoresponse when configured as a photoconductor device.

We report on the hyperdoping of silicon with selenium obtained by ion implantation followed by flash lamp annealing. It is shown that the degree of crystalline lattice recovery of the implanted layers and the Se substitutional fraction depend on the pulse duration and energy density of the flash. While the annealing at low energy densities leads to an incomplete recrystallization, annealing at high energy densities results in a decrease of the substitutional fraction of impurities. The electrical properties of the implanted layers are well-correlated with the structural properties resulting from different annealing processing.

In the present work, we report the 25 MeV oxygen irradiation effects in n-type single crystal β-Ga2O3 at different fluences. We demonstrate that the symmetric stretching modes and bending vibrations of GaO4 and GaO6 units are impaired upon increasing O irradiation fluence. Blue and green photoluminescence emission bands are found to be mainly associated with gallium-oxygen divacancies, gallium vacancies and oxygen interstitials. The increase of optically active centers at low fluence and the photoluminescence quenching at high fluence are ascribed to the reduction of carrier density and the production of non-radiative recombination centers, respectively. The results envisage the possibility of obtaining pre-designed spectral behaviours by varying the oxygen irradiation fluence.

Mid-infrared plasmonic sensing allows the direct targeting of molecules relevance in the so-called “vibrational fingerprint region”. Presently, heavily doped semiconductors exhibiting the potential to replace and outperform metals in the mid- infrared frequency range to revolutionize plasmonic devices. In this work, we demonstrate the occurrence of localized surface plasmon resonances (LSPR) in Te heavily-doped Si layers developed by ion implantation combined with flash lamp annealing. We fabricate micrometer-sized antennas out of the Te-hyperdoped Si layers by electron-beam lithography and reactive ion etching processes. The optical response characterized by Fourier-transform infrared (FTIR) spectroscopy demonstrates the enhancement of localized plasmon resonances in antennas, from mid- to far- infrared frequency range. Our results set a new path toward integration of plasmonic sensors with the one-chip CMOS platform.

Hyperdoping has emerged as a promising method for designing semiconductors with unique physical properties. In general, these properties are primarily determined by the lattice location of the impurity atoms in the host material. In this contribution, the lattice location of implanted chalcogens in Si was experimentally determined by means of Rutherford backscattering/channeling (RBS/C). The implication on the electrical activation of chalcogens in Si will be discussed with respect to the Hall effect results. The obtained carrier concentration and the RBS angular scans across the and axis reveal that the electrically active/inactive concentration of Te correlates with the concentration of substitutional/interstitial site Te atoms. Surprisingly, contrary to the general belief, we find that the interstitial fraction decreases with increasing impurity concentration. This abnormal dependence of lattice location and electrical activation on impurity concentration suggests that the formation energy for the substitutional Te or Te-Te dimers in Si is lower than for the interstitial Te. This assumption is theoretically verified by the first-principles calculations.

Full integration of Ge-based alloys like GeSn with complementary-metal-oxide-semiconductor technology would require the fabrication of p- and n-type doped regions for both planar and tri-dimensional device architectures which is challenging using in situ doping techniques. In this work, we report on the influence of ex situ doping on the structural, electrical and optical properties of GeSn alloys. n-type doping is realized by P implantation into GeSn alloy layers grown by molecular beam epitaxy (MBE) followed by flash lamp annealing. We show that effective carrier concentration of up to 1 × 10^19 cm−3 can be achieved without affecting the Sn distribution. Sn segregation at the surface accompanied with an Sn diffusion towards the crystalline/amorphous GeSn interface is found at P fluences higher than 3 × 10^15 cm−2 and electron concentration of about 4 × 10^19 cm−3. The optical and structural properties of ion-implanted GeSn layers are comparable with the in situ doped MBE grown layers.

Presently,room-temperature broadband Si-based photodetectors are required for Si photonic systems.Here,we demonstrate roomtemperature sub-band gap photoresponse of photodiodes based on Si hyperdoped with Te.The epitaxially recrystallized Te-hyperdoped Si layers are developed by ion implantation combined with pulsed laser melting and incorporate Te concentrations beyond the solid solubility limit.An insulator-to-metal transition driven by increasing Te concentration accompanied with a band gap renormalization is observed.The optical absorptance is found to increase monotonically with increasing Te concentration and extends well into the mid- and far- infrared regions.This work contributes to establish room temperature Si-based broadband infrared photonic system.

Semiconducting nanowires (NWs) hold promises for functional nanoscale devices [1]. Although several applications have been demonstrated in the areas of electronics, photonics and sensing, the doping of NWs remains challenging. Ion implantation is a standard doping method in top-down semiconductor industry, which offers precise control over the areal dose and depth profile as well as allows for the doping of all elements of the periodic table even beyond their equilibrium solid solubility [2]. Yet its major disadvantage is the concurrent material damage. A subsequent annealing process is commonly used for the healing of implant damage and the electrical activation of dopants. This step, however, might lead to the out-diffusion of dopants and eventually the degradation of NWs because of the low thermal stability caused by the large surface–area-to-volume ratio. In this work, we report on non-equilibrium processing for controlled doping of drop-casted Si/SiO2 core/shell NWs with shallow- and deep-level dopants below and above their equilibrium solid solubility. The approach lies on the implantation of either shallow-level dopants, such as B and P, or deep-level dopants like Se followed by millisecond flash lamp annealing. In case of amorphization upon high-fluence implantation, recrystallization takes place via a bottom-up template-assisted solid phase epitaxy. Non-equilibrium Se concentrations lead to intermediate-band Si/SiO2 core/shell NWs that have room-temperature sub-band gap photoresponse when configured as a photoconductor device [3]. Alternatively, the formation of a cross-sectional p-n junction is demonstrated by co-implanting P and B in individual NWs at different depth along the NW core. [1] Peidong Yang, Ruoxue Yan, and Melissa Fardy, Nano Lett. 2010, 10, 1529–1536 [2] Michiro Sugitani, Rev. Sci. Instrum. 2014, 85, 02C315 [3] Y. Berencén, et al. Adv. Mater. Interfaces 2018, 5, 1800101

Presently, room-temperature infrared sub-band-gap photoresponse in Si is of great interest for the development of on-chip complementary-metal-oxide-semiconductor (CMOS)-compatible photonic platforms [1]. One of the most promising approaches to further extend the photoresponse of Si to the mid- and far-infrared (MIR/FIR) ranges consists of introducing deep-level dopants into the Si band gap at concentrations in excess of the solid solubility limit [2]. In this work, we demonstrate strong room-temperature sub-band-gap photoresponse of photodiodes based on Si hyperdoped with tellurium [3]. A CMOS-compatible approach of combining ion implantation with pulsed laser melting was applied to synthesize single-crystalline and epitaxial Te-hyperdoped Si layers with a Te concentration five orders of magnitude above the solid solubility limit. Driven by increasing Te concentration, both the insulator-to-metal transition and a band-gap renormalization are observed. The sub-band optical absorptance in the resulting Te-hyperdoped Si layers is found to increase monotonically with increasing Te concentration and extends well into the MIR/FIR ranges (1.4 to 25 μm). Importantly, the MIR/FIR optoelectronic response from Te-hyperdoped Si photodiodes is demonstrated to be related with known Te deep-energy levels into the Si band-gap. This work contributes to pave the way towards establishing a Si-based broadband infrared photonic system operating at room temperature.

Presently, silicon photonics requires photodetectors that are sensitive in a broad infrared range, can operate at room temperature, and are suitable for integration with the existing Si-technology process. Here, we demonstrate strong room-temperature sub-band-gap photoresponse of photodiodes based on Si hyperdoped with tellurium. The epitaxially recrystallized Te-hyperdoped Si layers are developed by ion implantation combined with pulsed-laser melting and incorporate Te-dopant concentrations several orders of magnitude above the solid solubility limit. With increasing Te concentration, the Te-hyperdoped layer changes from insulating to quasi-metallic behavior with a finite conductivity as the temperature tends to zero. The optical absorptance is found to increase monotonically with increasing Te concentration and extends well into the mid-infrared range. Temperature-dependent optoelectronic photoresponse unambiguously demonstrates that the extended infrared photoresponsivity from Te-hyperdoped Si p-n photodiodes is mediated by a Te intermediate band within the upper half of the Si band gap. This work contributes to pave the way toward establishing a Si-based broadband infrared photonic system operating at room temperature., Comment: 18 pages, 7 figures

Hyperdoping silicon with chalcogen atoms is a topic of increasing interest due to the strong sub-band gap absorption exhibited by the resulting materials, which can be exploited to develop infrared photodectectors and intermediate band solar cells [1-3]. In our work, tellurium-hyperdoped silicon layers have been fabricated by ion implantation followed by flash lamp annealing (FLA) or pulsed-laser melting (PLM). The Rutherford backscattering spectrometry / Channeling (RBS/C) results reveal the high-quality recrystallization of tellurium implanted silicon by both FLA and PLM. From the transport measurements, an insulator-to-metal transition is observed with increasing tellurium concentration. Moreover, the ellipsometry measurements show that the band gap narrows with increasing doping concentration. And the Fourier transform infrared (FTIR) spectroscopy show that tellurium hyperdoped Si has strong infrared absorption. All these results give us a signal that hyperdoped silicon with tellurium could enable silicon-based optoelectronics in the infrared band. [1] Kim, T. G., et al., Appl. Phys. Lett. 88, 241902 (2006) [2] Tabbal, M., et al., Appl. Phys. A 98, 589–594 (2010) [3] Umezu, I., et al., J. Appl. Phys. 113, 213501 (2013)

The hyperdoping of semiconductors consists of introducing dopant concentrations far above the equilibrium solubility limits. This results in a broadening of dopant energy levels into an impurity or intermediate band. We have recently demonstrated that hyperdoping bulk Si with Se shows promise for Si-based short-wavelength infrared photodetectors [1]. Lately, silicon nanowires (NWs) have gained increasing importance as building blocks for nanodevices like field-effect transistors, light emitting devices and photovoltaic cells [2, 3]. Therefore, the comparison between hyperdoping Si nanowires and bulk Si is a common issue to be examined, which comes along with the transition from a bulk material to semiconductor NWs. In this work, we report on non-equilibrium processing for controlled hyperdoping of Si/SiO2 core/shell nanowires previously synthesized by the vapor-liquid-solid method. Our approach is based on Se implantation of the upper half of NWs followed by millisecond flash lamp annealing, which allows for a bottom-up template-assisted recrystallization of the amorphized parts of the NWs via explosive solid-phase epitaxy. The Se-hyperdoped Si NWs are successfully recrystallized and accommodate Se concentrations as high as 1021 cm-3. As a proof of device concept, a single Se-hyperdoped NW-based IR photoconductor is shown. In this way, the combination of ion implantation and flash lamp annealing as a promising nanoscale hyperdoping technology is successfully established. [1] Y. Berencén, S. Prucnal, Fang Liu, I. Skorupa, R. Hübner, L. Rebohle, S. Zhou, H. Schneider, M. Helm, and W. Skorupa, “Room-temperature short-wavelength infrared Si photodetector,” Sci. Rep. 7, 43688 (2017). [2] B. Tian, T. Cohen-Karni, Q. Qing, X. Duan, P. Xie and C.M. Lieber, “Three-dimensional, flexible nanoscale field-effect transistors as localized bioprobes,” Science 329, 831 (2010). [3] T. J. Kempa, B. Tian, D.R. Kim, J. Hu, X. Zheng and C.M. Lieber, “Single and tandem axial p-i-n nanowire photovoltaic devices,” Nano Lett. 8, 3456 (2008).

Silicon hyperdoped with chalcogens beyond the equilibrium solubility limit exhibits sub-band gap optical absorption, presenting a potential material for silicon-based optoelectronic applications [1-3]. In our work, tellurium hyperdoped silicon was obtained by ion implantation combined with pulsed laser melting. The crystallization of implanted layers and the lattice location of impurities in silicon matrix were determined by the Rutherford backscattering spectrometry / channeling (RBS/C). The chemical states of tellurium dopants in tellurium-hyperdoped silicon were probed by the tellurium K-edge X-ray absorption fine structure spectroscopy. The electrical transport reveals the insulator-to-metal transition (IMT) in tellurium-hyperdoped silicon, which is confirmed and understood by using calculations based on the density functional theory. However, the critical tellurium concentration for IMT is much higher than the calculated value. The lattice location results suggest that a significant fraction of the tellurium atoms form dimers, which are electrically deactivated. After considering this fraction, the critical concentration claimed from the DFT calculation is consistent with the number of electrically activated tellurium atoms. [1] T. G. Kim, J.M. Warrender, M. J. Aziz, Applied Physics Letters 88(24), 2006, 1850. [2] M. Tabbal, T. G. Kim, D. N. Woolf, et al. Applied Physics A 98(3), 2010, 589-594. [3] Y. Berencén, S. Prucnal, L. Fang, et al. Scientific Reports 7, 2017, 43688.

Chalcogen-hyperdoped silicon has been a topic of great interest due to its potential optoelectronic applications owing to the sub-band gap absorption [1-3]. In our work, tellurium hyperdoped Si was fabricated by ion-implantation with different fluences ranging from 1.09×1015 to 1.25×1016 cm-2 followed by pulsed laser melting (PLM). The Rutherford backscattering spectrometry / Channeling (RBS/C) results reveal the high-quality recrystallization of tellurium implanted silicon by PLM. From the transport measurements, an insulator-to-metal transition is observed with increasing tellurium concentration. Moreover, the ellipsometry measurements show that the band gap narrows with increasing tellurium doping concentration. And the Fourier transform infrared (FTIR) spectroscopy show that tellurium hyperdoped Si has strong infrared absorption. This gives us a signal that hyperdoped silicon with tellurium could enable silicon-based optoelectronics in the infrared band.

Recently it was suggested that Au doping in Si can be realized by ion implantation and pulsed laser melting. The sub-band-gap optoelectronic response is observed and increases with the implanted Au concentration [1]. In our work, Au implanted Si was fabricated by ion-implantation with three different fluences of 7×1014 cm-2, 1.4×1015 cm-2 and 2.1×1015 cm-2, followed by pulsed laser melting. The Raman spectrum results confirm the high-quality recrystallization of the Au implanted layer. And the Rutherford backscattering spectrometry / Channeling reveal that Au atoms diffused to the near surface region. In addition the detailed angular scans along Si [001] reveal that Au atoms are mostly in the interstitial lattice sites. From the transport measurements, a p-type conductivity and an increasing carrier concentration are observed in the implanted layer. Moreover, the transmission and reflection were measured using near infrared spectroscopy (NIR) to quantify the sub-band-gap absorptance in the hyperdoped silicon. In the Au implanted layer the spectral response extends to wavelengths as long as 3.2 μm. However, the sub-band-gap absorptance has no dependence on the Au fluence or the carrier concentration. [1] Mailoa, Jonathan P., et al., Nat. Commun. 5, 3011 (2014)

GeSn with quasi-direct band gap is one of the most promising semiconductor materials for light emitters integrated with CMOS technology. The equilibrium solid solubility limit (SSL) of Sn in Ge is in the range of 0.5 % and the predicted theoretical Sn concentration needed for the direct band gap formation is above 5 %. This means that GeSn with direct band gap is metastable and any related material process cannot be thermal equilibrium. Here we propose to utilize strongly non-equilibrium processing i.e. ion implantation followed by millisecond range flash lamp annealing (FLA), for doping and the formation of Ohmic contacts with low contact resistance on Ge0.95Sn0.05. The effective carrier concentration in P+ implanted Ge0.95Sn0.05 layer followed by FLA for 3 ms is above 5×10^19cm-3 with a specific contact resistance rc=4×10^-6Ωcm2. NiGe for Ohmic contact is made by Ni diffusion into GeSn during a single 3 ms long flash pulse. TEM images reveal that NiGe is polycrystalline but with an atomically sharp interface between the metal contact and GeSn. The influence of non-equilibrium processing (ion implantation and FLA) on the optical, electrical and microstructural properties of the GeSn layer grown by MBE on Si will be discussed in details.

A combined experimental and theoretical study on the electroluminescent excitation mechanism for trivalent erbium (Er3+) ions in a silicon-rich nitride (SiNx) host is presented. Direct impact by hot electrons is demonstrated to be the fundamental excitation mechanism. The Er3+ excitation by energy transfer from silicon nanostructures and/or defects is shown to be marginal under electrical pumping. A bilayer structure made of a SiO2 electron-accelerating layer and an Er-implanted SiNx layer has been sandwiched between a metal–insulator–semiconductor structure with a highly doped N-type silicon substrate and an indium–tin–oxide window functioning as a transparent electrode. Monte Carlo (MC) simulations are used to model hot electron transport in the proposed device structure. Acoustic, polar and non-polar optical electron–phonon scattering mechanisms are considered as well as a new scattering process related to the trapping/detrapping on energetically shallow traps in the band gap of silicon nitride. For SiO2 layers around 20 nm-thick and beyond, the number and kinetic energy of hot electrons before entering the SiNx layer are maximal. A significant enhancement of the 1.54 μm electroluminescence power efficiency of two orders of magnitude is observed in devices composed of a 20 nm-thick SiO2 layer compared to those composed of 10 nm-thick SiO2. We demonstrate by MC simulations that such a difference, in terms of power efficiency, is ascribed to the high-energy tail of the hot electron energy distribution, which becomes more pronounced as the SiO2 electron-accelerating layer thickness increases. It is also unveiled that direct excitation of the 1.54 μm Er3+ main radiative transition requiring an excitation energy of only 0.8 eV is inefficient, and that the major part of the Er3+ ions are excited via higher level energy states. The obtained results are sufficiently consistent to be extended to other trivalent rare-earth ions inside similar insulating material environments.

The development of room-temperature Si infrared photodetectors, whose range of detection lies on the traditional telecommunication wavelengths around 1300 nm and 1550 nm, is of paramount importance for optical communications, integrated photonics, sensing and medical imaging applications [1]. The typical peak photoresponse of conventional Si photodetectors is between 700 and 900 nm, which is primarily limited by the 1.12 eV-Si band gap. However, such intrinsic material limitation can be overcome by introducing transition metals or chalcogens into the Si band gap at concentrations far above those obtained at equilibrium conditions [1, 2]. This new class of hyperdoped materials with a donor impurity band has been postulated as a viable route to extend the Si photoresponse at the infrared spectral region [3]. In this work, we report on the significant room-temperature photoresponse and performance at the two primary telecommunication wavelengths as exhibited by hyperdoped Si p-n photodiodes fabricated by Se implantation followed by millisecond flash lamp annealing (FLA). The FLA approach in the millisecond range allows for a solid-phase epitaxy that has been reported to be superior to liquid-phase epitaxy induced during pulsed laser annealing [2]. The success of our devices is primarily based on the high quality of the developed n-type hyperdoped material, which is single-phase single crystal with high electrical activation, without surface segregation of Se atoms and with an optically flat surface. [1] J. P. Mailoa, A. J. Akey, C. B. Simmons, D. Hutchinson, J. Mathews, J. T. Sullivan, D. Recht, M. T. Winkler, J. S. Williams, J. M. Warrender, P. D. Persans, M. J. Aziz, and T. Buonassisi, Nat. Commun. 5, 3011 (2014). [2] S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, C. Baehtz, M. Posselt, W. Skorupa, and M. Helm, Sci. Rep. 5, 8329 (2015). [3] I. Umezu, J. M. Warrender, S. Charnvanichborikarn, A. Kohno, J. S. Williams, M. Tabbal, D. G. Papazoglou, X. C.Zhang, and M. J. Aziz, J. Appl. Phys. 113, 213501 (2013).

The development of room-temperature short-wavelength infrared Si photodetectors is of paramount importance for optical communications, integrated photonics, sensing and medical imaging applications [1]. The typical peak photoresponse of conventional Si photodetectors is between 700 and 900 nm, which is mainly limited by the 1.12 eV-Si indirect band gap. Nevertheless, such intrinsic material limitation can be circumvented by introducing transition metals or chalcogens into the Si band gap at concentrations far above those obtained at equilibrium conditions [1, 2]. This new class of hyperdoped materials with a donor impurity band has been postulated as a viable route to extend the Si photoresponse at the short-wavelength infrared spectral region [3]. In this work, we report on the significant room-temperature photoresponse and performance at wavelengths as long as 3100 nm as exhibited by hyperdoped Si p-n photodiodes fabricated by Se implantation followed by flash lamp annealing (FLA). The FLA approach in the millisecond range allows for a solid-phase epitaxy that has been reported to be superior to liquid-phase epitaxy induced during pulsed laser annealing [2]. The success of our devices is primarily based on the high quality of the developed n-type hyperdoped material, which is single-phase single crystal with high electrical activation, without surface segregation of Se atoms and with an optically flat surface. [1] J. P. Mailoa, A. J. Akey, C. B. Simmons, D. Hutchinson, J. Mathews, J. T. Sullivan, D. Recht, M. T. Winkler, J. S. Williams, J. M. Warrender, P. D. Persans, M. J. Aziz, and T. Buonassisi, Nat. Commun. 5, 3011 (2014). [2] S. Zhou, F. Liu, S. Prucnal, K. Gao, M. Khalid, C. Baehtz, M. Posselt, W. Skorupa, and M. Helm, Sci. Rep. 5, 8329 (2015). [3] I. Umezu, J. M. Warrender, S. Charnvanichborikarn, A. Kohno, J. S. Williams, M. Tabbal, D. G. Papazoglou, X. C.Zhang, and M. J. Aziz, J. Appl. Phys. 113, 213501 (2013)

Independent of the type of doping, it is challenging to achieve in semiconductors an effective carrier concentration much above 10^20 /cm3. On the other hand, the successful realization of defect free n-type and p-type ultra-doped Ge layers will enable a range of devices from sensors to quantum computers. In the case of conventional doping techniques (using equilibrium processing) the maximum carrier concentration is limited by the out-diffusion of dopants, a relatively low solid solubility limit, clustering and self-compensation processes. To overcome such limitations we have utilised strong nonequilibrium process consisting of an ion beam implantation to introduce dopants into Ge and rear-side millisecond range flash lamp annealing (FLA) for recrystallization of implanted layer and dopant activation. In contrast to conventional annealing procedures, rear-side FLA leads to full recrystallization of Ge and dopant activation independent of the pre-treatment. The maximum carrier concentration is well above 10^20 /cm3 for n-type and above 10^21 /cm3 for p-type dopants. The so-fabricated n-type Ge can be used in the field of mid-infrared plasmonics which has not been accessible by group-IV semiconductors. Single crystalline n-type Ge with carrier concentrations as high as 2.2×10^20 /cm3 displays a room-temperature plasma frequency above 1850 /cm1 (?=5.4 ?m), which is the highest value ever reported for n-type Ge. In the case of Ga implanted Ge the maximum effective carrier concentration measured at 3K is 1.1×10^21 /cm3 which is two times higher than the solid solubility limit of Ga in Ge. Our p-type Ge is defect and cluster free and shows the superconductivity at Tc = 0.95 K. These results base on the successful combination of ion beam implantation followed by the novel approach consisting of millisecond range rear-FLA. This work has been partially supported by the EU 7th Framework Programme "EAgLE" (REGPOT-CT-2013-316014).

Exploiting plasmonics for mid-IR sensing purposes has become an increasing area of research. The reason is that many molecules present molecular vibrational resonances, which provide spectral fingerprints in the near- and mid-IR region [1, 2]. Of particular interest is the gas detection, diagnostic and medical care. To this day, strong plasmon resonances in the visible and near-IR spectral range have been identified in nanostructured metals such as silver, aluminum and gold [3]. In principle, heavily doped semiconducting materials like Si or Ge could be an interesting alternative to replace metals due to their compatibility with CMOS technology. Indeed, the possibility to control the plasmon resonance frequency in semiconductors via the carrier density opens new route for near- and mid-IR detectors. In this work, we report on the strong mid-IR plasmon absorption from heavily P-doped Ge thin films obtained by non-equilibrium thermal processing. Ultra-doped Ge layers were fabricated by ion implantation of P ions followed by rear-side flash lamp annealing in the millisecond range. This approach, in contrast to conventional annealing procedures, leads to full recrystallization of Ge films and high P activation irrespective of pre-treatment. In this way, single crystalline Ge thin films free of defects with carrier concentration much above 1×1020 cm-3 and carrier mobility above 260 cm2/(V·s) were obtained. The mid-IR plasmon spectral response at room temperature from those samples was characterized by means of Fourier transform infrared spectroscopy. It is proven that the position of the signal from the plasmon resonance frequency can be tuned as a function of the P concentration. Keywords: plasmonics, heavily doped n-type Ge, flash-lamp annealing. [1] A. G. Brolo, Nat. Photonics 6, 709 (2012). [2] N. Liu, M. Mesch, T. Weiss, M. Hentschel, and H. Giessen, Nano Lett. 10, 2342 (2010). [3] G. Konstantatos and E. H. Sargent, Nat. Nanotechnology 5, 391 (2010).

Er-based, electrically driven light emitters, which can easily be integrated into Si-based circuitries, are of great interest for a broad range of applications, especially in the field of telecommunication and sensing. This work investigates the electrical and electroluminescence (EL) properties of Er-implanted MOS structures with different designs of the dielectric stack. The dielectric stack is essentially composed of a 30 nm thick SiO2 layer and a 40 nm thick host matrix for the Er ions made of Si-rich SiO2, silicon nitride or Si-rich silicon nitride. All structures implanted with Er show intense EL around 1550 nm which is excited by impact excitation of hot electrons. We compare the different host matrices regarding the EL efficiency, the EL excitation cross section, the EL decay time, the fraction of excited Er ions, the EL quenching cross section and the operation lifetime. This comparison reveals fundamental properties of the EL mechanism and addresses the current problems of this type of Si-based light emitter to achieve the performance level of compound semiconductors with a direct bandgap.

The suitability of rare earth doped metal-oxide-semiconductor structures for optoelectronic applications is investigated. To do so, several Tb- and Er-doped devices with different designs and fabricated by different methods are compared among each other with respect to their electroluminescence (EL) properties. In detail, the investigated devices show EL power efficiencies between 2×10-4 and 2×10-3 which, taken individually for Tb and Er, have a linear dependence on the EL decay time for low and medium injection current densities. The excited fraction of Er ions is significantly higher than that of Tb ions and achieves a maximum value of 50% (with a maximum uncertainty factor of 2.25) under optimum conditions.

Rare earth doped metal-oxide-semiconductor (MOS) structures are of great interest for Si-based light emission. However, several physical limitations make it difficult to achieve the performance of light emitters based on compound semiconductors. To address this point, in this work the electroluminescence (EL) excitation and quenching mechanism of Er-implanted MOS structures with different designs of the dielectric stack are investigated. The devices usually consist of an injection layer made of SiO2 and an Er-implanted layer made of SiO2, Si-rich SiO2, silicon nitride or Si-rich silicon nitride. All structures implanted with Er show intense EL around 1540 nm with EL power efficiencies in the order of 2×10-3 (for SiO2:Er) or 2×10-4 (all other matrices) for lower current densities. The EL is excited by the impact of hot electrons with an excitation cross section in the range of 0.5-1.5×10-15 cm-2. Whereas the fraction of potentially excitable Er ions in SiO2 can reach values up to 50%, five times lower values were observed for other matrices. The decrease of the EL decay time for devices with Si-rich SiO2 or Si nitride compared to SiO2 as host matrix implies an increase of the number of defects adding additional non-radiative de-excitation paths for Er3+. For all investigated devices EL quenching cross sections in the 10-20 cm2 range and charge-to-breakdown values in the range of 1-10 Ccm-2 were measured. For the present design with a SiO2 acceleration layer, thickness reduction and the use of different host matrices did not improve the EL power efficiency or the operation lifetime, but strongly lowered the operation voltage needed to achieve intense EL.

Er-based light emitters, which can be electrically driven and easily integrated into Si-based circuitries, are of great interest for a broad palette of applications, especially in the field of telecommunication and sensing. Among the different approaches Er-implanted MOS devices feature their excellent compatibility to standard CMOS processes and the reproducibility of the implantation process. However, at present such devices do achieve neither the efficiency nor the operation lifetime usually required for such applications. In this study we compare various designs of Er-implanted MOS devices with respect to their electroluminescence efficiency and electrical operation lifetime. The different designs comprise devices implanted with Er alone or co-implanted with Si and Er, various single and multilayer systems and different host matrices for Er, namely SiO2 or Si-rich Si3N4. Despite the different design parameters, a strong correlation between efficiency and operation lifetime is found. This behavior is explained by the ambivalent role of hot electrons which play a key role both for the efficient excitation of erbium and for the oxide degradation.

Charge transport and electroluminescence mechanisms in Si-rich Si oxynitride/silicon oxide (SRON/SiO2) superlattices deposited on p-type Si substrate are reported. The superlattice structures were deposited by plasma-enhanced chemical-vapor deposition and subsequently annealed at 1150 °C to precipitate and crystallize the Si excess into Si nanocrystals. The dependence of the electrical conduction on the applied voltage and temperature was found to be well described by a Poole-Frenkel transport mechanism over a wide voltage range. On the other hand, the observed dependence of the electroluminescence on the SRON layer thickness is a clear proof of quantum confinement and was attributed to an excitonic radiative recombination taking place in the confined states within the Si quantum dots. A model is proposed based on thermal hopping of electrons between the quantum dots acting as trap states (Poole-Frenkel). A correlation between carrier transport and electroluminescence has been established considering impact ionization of high-kinetic energy electrons on the Si quantum dots.

This work reports the dynamical thermal behavior of lasing microspheres placed on a dielectric substrate while they are homogeneously heated-up by the top-pump laser used to excite the active medium. The lasing modes are collected in the far-field and their temporal spectral traces show characteristic lifetimes of about 2 ms. The latter values scale with the microsphere radius and are independent of the pump power in the studied range. Finite-Element Method simulations reproduce the experimental results, revealing that the thermal dynamics is dominated by the heat dissipated towards the substrate through the medium surrounding the contact point. The characteristic system scale regarding thermal transport is of few hundreds of nanometers, thus enabling an effective toy model for investigating heat conduction in non-continuum gaseous media and near-field radiative energy transfer., 13 pages, 5 figures

We demonstrate the integration of Nd3+ doped Barium-Titanium-Silicate microsphere lasers with a Silicon Nitride photonic platform. Devices with two different geometrical configurations for extracting the laser light to buried waveguides have been fabricated and characterized. The first configuration relies on a standard coupling scheme, where the microspheres are placed over strip waveguides. The second is based on a buried elliptical geometry whose working principle is that of an elliptical mirror. In the latter case, the input of a strip waveguide is placed on one focus of the ellipse, while a lasing microsphere is placed on top of the other focus. The fabricated elliptical geometry (ellipticity=0.9) presents a light collecting capacity that is 50% greater than that of the standard waveguide coupling configuration and could be further improved by increasing the ellipticity. Moreover, since the dimensions of the spheres are much smaller than those of the ellipses, surface planarization is not required. On the contrary, we show that the absence of a planarization step strongly damages the microsphere lasing performance in the standard configuration., Comment: 10 pages, 4 figures