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The impact of elemental boron (B) doping on the structural, optical, and magnetotransport properties of epitaxial Ge/AlAs/GaAs(001) heterostructures, grown by solid-source molecular beam epitaxy, was comprehensively investigated. Cross-sectional transmission electron microscopy analysis revealed atomically abrupt Ge:B/AlAs and AlAs/GaAs heterointerfaces and a lack of observable long-range defect formation or B segregation in the epitaxial Ge:B layer. Spectral broadening observed in the measured temperature-dependent photoluminescence spectra suggested valence band mixing during recombination, implying a splitting of the valence band heavy- and light-hole degeneracy due to residual strain resulting from substitutional B incorporation in the Ge epilayer. Temperature-dependent magnetotransport analysis of the B-doped Ge thin films exhibited the tell-tale signature of antilocalization, indicating observable spin–orbit interaction in the Ge:B system. Moreover, the temperature- and magnetic field-dependent magnetotransport results indicate the presence of single-carrier, p-type conduction in the Ge:B film, further affirming the successful incorporation and activation of B at a high concentration (∼4 × 1019 cm−3) and elimination of parallel conduction via the large-bandgap AlAs buffer. Together, these results provide insights into the effects of heavy doping (via elemental solid-source doping) on Ge-based heterostructures and their feasibility in future electronic and photonic applications. [ABSTRACT FROM AUTHOR]

The impact of bulk and surface defect states on the vibrational and optical properties of step-graded epitaxial GaAs1-ySby (0 ≤ y ≤ 1) materials with and without chemical surface treatment by (NH4)2S was investigated. Tunable antimony (Sb) composition GaAs1-ySby epitaxial layers, grown by solid source molecular beam epitaxy (MBE), were realized on GaAs and Si substrates by varying key growth parameters (e.g., Sb/Ga flux ratio, growth temperature). Raman and photoluminescence (PL) spectroscopic analysis of (NH4)2S-treated GaAs1-ySby epitaxial layers revealed composition-independent Raman spectral widths and enhanced PL intensity (1.3×) following (NH4)2S surface treatment, indicating bulk defect-minimal epitaxy and a reduction in the surface recombination velocity corresponding to reduced surface defect sites, respectively. Moreover, quantification of the luminescence recombination mechanisms across a range of measurement temperatures and excitation intensities (i.e., varying laser power) indicate the presence of free-electron to neutral acceptor pair or Sb-defect-related recombination pathways, with detectable bulk defect recombination discernible only in binary GaSb PL spectra. In addition, PL analysis of the short- and long-term thermodynamic stability of sulfur-treated GaAs1-ySby/Al2O3 heterointerfaces revealed an absence of quantifiable atomic interdiffusion or native oxide formation. Leveraging the combined Raman and PL analysis herein, the quality of the heteroepitaxial step-graded epitaxial GaAs1-ySby materials can be optimized for optical devices. [ABSTRACT FROM AUTHOR]

In this paper, we benchmark the read/write performance and standby power of several static random access memory (SRAM) cell architectures utilizing 45-nm Si CMOS MOSFET and/or tensile-strainedGe/InGaAs tunnel FET (TFET) devices under low-voltage operation ( 0.2~\text V \le \vert V\text {DD}\vert \le 0.6 V). We then introduce a novel tensile-strained Ge/InGaAs TFET-based SRAM circuit using several access schemes and investigate the impact of cell access design on static and dynamic performance. SRAM cells utilizing outwardaccess transistors exhibit wide read andwrite static noise margins, but suffer from increased read delay times. A 7T SRAM cell architecture is proposed in order to resolve the degraded read delay time. Cell standby energy was found to exhibit a strong dependenceon operational voltage andGe strain state. Variation of theGe strain state from 1.5% to 3% resulted in an up to 98% reduction in cell standby energy ( \vert V\text {DD}\vert = 0.6 V) as compared with similar CMOS-based SRAM cells. These results demonstrate the superior performance of the proposed 7T TFET SRAM design for operation in the low- and ultralow-voltage regime. [ABSTRACT FROM PUBLISHER]

Novel strain-engineered staggered gap Ge/InxGa1–xAs heterojunction tunnel FETs (H-TFETs) are proposed and theoretically evaluated. Modulation of the indium alloy composition at the source–channel heterointerface resulted in 18.6\times and 16.9\times enhancement in I\mathrm{\scriptscriptstyle ON} for n- and p-channel Ge/InxGa1–xAs H-TFETs, respectively, as compared with strained Ge homojunction TFETs (p+-Ge/i-Ge/n+-Ge). The n-type H-TFETs (p+-Ge/i-InxGa1–xAs/n+-InxGa1–xAs) exhibited superior leakage suppression due to a larger tunneling barrier at the channel–drain interface. Moreover, the p-type H-TFETs (n+-InxGa1–xAs/i-Ge/p+-Ge) demonstrated a significant enhancement in I\mathrm{\scriptscriptstyle ON} due to an unequal shift in the conduction band edge as a result of doping-induced bandgap narrowing. The simulated tensile-strained Ge/InxGa1–xAs H-TFETs show a great promise for ultralow-power switches with high ON-state and low OFF-state current, providing a new path for low-power complimentary TFET logic. [ABSTRACT FROM PUBLISHER]

In this letter, we propose a novel interface fuse (iFuse) for low-power electrically programmable fuses in advanced CMOS applications. With an offset-landed metal-to-contact or contact-to-polysilicon structure, the iFuse can be programmed by substantially reduced current as compared to conventional fuses. A diagonal contact layout and the optical pattern correction scheme can further improve the cell stability as well as its programming characteristics. [ABSTRACT FROM PUBLISHER]

The indirect nature of silicon (Si) emission currently limits the monolithic integration of photonic circuitry with Si electronics. Approaches to circumvent the optical shortcomings of Si include band structure engineering via alloying (e.g., Si x Ge 1- x - y Sn y ) and/or strain engineering of group IV materials (e.g., Ge). Although these methods enhance emission, many are incapable of realizing practical lasing structures because of poor optical and electrical confinement. Here, we report on strong optoelectronic confinement in a highly tensile-strained (ε) Ge/In 0.26 Al 0.74 As heterostructure as determined by X-ray photoemission spectroscopy (XPS). To this end, an ultrathin (∼10 nm) ε-Ge epilayer was directly integrated onto the In 0.26 Al 0.74 As stressor using an in situ, dual-chamber molecular beam epitaxy approach. Combining high-resolution X-ray diffraction and Raman spectroscopy, a strain state as high as ε ∼ 1.75% was demonstrated. Moreover, high-resolution transmission electron microscopy confirmed the highly ordered, pseudomorphic nature of the as-grown ε-Ge/In 0.26 Al 0.74 As heterostructure. The heterointerfacial electronic structure was likewise probed via XPS, revealing conduction- and valence band offsets (Δ E C and Δ E V ) of 1.25 ± 0.1 and 0.56 ± 0.1 eV, respectively. Finally, we compare our empirical results with previously published first-principles calculations investigating the impact of heterointerfacial stoichiometry on the ε-Ge/In x Al 1- x As energy band offset, demonstrating excellent agreement between experimental and theoretical results under an As 0.5 Ge 0.5 interface stoichiometry exhibiting up to two monolayers of heterointerfacial As-Ge diffusion. Taken together, these findings reveal a new route toward the realization of on-Si photonics., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

In this work, an in situ SiO 2 passivation technique using atomic layer deposition (ALD) during the growth of gate dielectric TaSiO x on solid-source molecular beam epitaxy grown (100)In x Ga 1- x As and (110)In x Ga 1- x As on InP substrates is reported. X-ray reciprocal space mapping demonstrated quasi-lattice matched In x Ga 1- x As epitaxy on crystallographically oriented InP substrates. Cross-sectional transmission electron microscopy revealed sharp heterointerfaces between ALD TaSiO x and (100) and (110)In x Ga 1- x As epilayers, wherein the presence of a consistent growth of an ∼0.8 nm intentionally formed SiO 2 interfacial passivating layer (IPL) is also observed on each of (100) and (110)In x Ga 1- x As. X-ray photoelectron spectroscopy (XPS) revealed the incorporation of SiO 2 in the composite TaSiO x , and valence band offset (Δ E V ) values for TaSiO x relative to (100) and (110)In x Ga 1- x As orientations of 2.52 ± 0.05 and 2.65 ± 0.05 eV, respectively, were extracted. The conduction band offset (Δ E C ) was calculated to be 1.3 ± 0.1 eV for (100)In x Ga 1- x As and 1.43 ± 0.1 eV for (110)In x Ga 1- x As, using TaSiO x band gap values of 4.60 and 4.82 eV, respectively, determined from the fitted O 1s XPS loss spectra, and the literature-reported composition-dependent In x Ga 1- x As band gap. The in situ passivation of In x Ga 1- x As using SiO 2 IPL during ALD of TaSiO x and the relatively large Δ E V and Δ E C values reported in this work are expected to aid in the future development of thermodynamically stable high-κ gate dielectrics on In x Ga 1- x As with reduced gate leakage, particularly under low-power device operation., Competing Interests: The authors declare no competing financial interest.

Because of the high carrier mobility of germanium (Ge) and high dielectric permittivity of amorphous niobium pentoxide (a-Nb 2 O 5 ), Ge/a-Nb 2 O 5 heterostructures offer several advantages for the rapidly developing field of oxide-semiconductor-based multifunctional devices. To this end, we investigate the growth, structural, band alignment, and metal-insulator-semiconductor (MIS) electrical properties of physical vapor-deposited Nb 2 O 5 on crystallographically oriented (100), (110), and (111)Ge epilayers. The as-deposited Nb 2 O 5 dielectrics were found to be in the amorphous state, demonstrating an abrupt oxide/semiconductor heterointerface with respect to Ge, when examined via low- and high-magnification cross-sectional transmission electron microscopy. Additionally, variable-angle spectroscopic ellipsometry and X-ray photoelectron spectroscopy (XPS) were used to independently determine the a-Nb 2 O 5 band gap, yielding a direct gap value of 4.30 eV. Moreover, analysis of the heterointerfacial energy band alignment between a-Nb 2 O 5 and epitaxial Ge revealed valance band offsets (ΔE V ) greater than 2.5 eV, following the relation ΔE V (111) > ΔE V (110) > ΔE V (100) . Similarly, utilizing the empirically determined a-Nb 2 O 5 band gap, conduction band offsets (ΔE C ) greater than 0.75 eV were found, likewise following the relation ΔE C (110) > ΔE C (100) > ΔE C (111) . Leveraging the reduced ΔE C observed at the a-Nb 2 O 5 /Ge heterointerface, we also perform the first experimental investigation into Schottky barrier height reduction on n-Ge using a 2 nm a-Nb 2 O 5 interlayer, resulting in a 20× increase in reverse-bias current density and improved Ohmic behavior.

Mixed-anion, GaAs1-ySby metamorphic materials with tunable antimony (Sb) compositions extending from 0 to 100%, grown by solid source molecular beam epitaxy (MBE), were used to investigate the evolution of interfacial chemistry under different passivation conditions. X-ray photoelectron spectroscopy (XPS) was used to determine the change in chemical state progression as a function of surface preclean and passivation, as well as the valence band offsets, conduction band offsets, energy band parameters, and bandgap of atomic layer deposited Al2O3 on GaAs1-ySby for the first time, which is further corroborated by X-ray analysis and cross-sectional transmission electron microscopy. Detailed XPS analysis revealed that the near midpoint composition, GaAs0.45Sb0.55, passivation scheme exhibits a GaAs-like surface, and that precleaning by HCl and (NH4)2S passivation are mandatory to remove native oxides from the surface of GaAsSb. The valence band offsets, ΔEv, were determined from the difference in the core level to the valence band maximum binding energy of GaAs1-ySby. A valence band offset of >2 eV for all Sb compositions was found, indicating the potential of utilizing Al2O3 on GaAs1-ySby (0 ≤ y ≤ 1) for p-type metal-oxide-semiconductor (MOS) applications. Moreover, Al2O3 showed conduction band offset of ∼2 eV on GaAs1-ySby (0 ≤ y ≤ 1), suggesting Al2O3 dielectric can also be used for n-type MOS applications. The surface passivation of GaAs0.45Sb0.55 materials and the detailed band alignment analysis of Al2O3 high-κ dielectrics on tunable Sb composition, GaAs1-ySby materials, provides a pathway to utilize GaAsSb materials in future microelectronic and optoelectronic applications.

Broken-gap InAs/GaSb strain balanced multilayer structures were grown by molecular beam epitaxy (MBE), and their structural, morphological, and band alignment properties were analyzed. Precise shutter sequence during the MBE growth process, enable to achieve the strain balanced structure. Cross-sectional transmission electron microscopy exhibited sharp heterointerfaces, and the lattice line extended from the top GaSb layer to the bottom InAs layer. X-ray analysis further confirmed a strain balanced InAs/GaSb multilayer structure. A smooth surface morphology with surface roughness of ∼0.5 nm was demonstrated. The effective barrier height -0.15 eV at the GaSb/InAs heterointerface was determined by X-ray photoelectron spectroscopy, and it was further corroborated by simulation. These results are important to demonstrate desirable characteristics of mixed As/Sb material systems for high-performance and low-power tunnel field-effect transistor applications.