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In-depth understanding of lithium (Li) diffusion barriers is a crucial factor for enabling Li-ion based devices like 3D thin-film batteries and synaptic redox transistors integrated on silicon substrates. Diffusion of Li-ions into the silicon can damage surrounding components, detach the device itself, lead to battery capacity loss, and cause uncontrolled change of the transistor channel conductance. In this study, we analyze for the first time ultrathin 10 nm titanium nitride (TiN) films as bifunctional Li-ion diffusion barrier and current collector. Thermal atomic layer deposition (ALD) and pulsed chemical vapor deposition (pCVD) are employed for manufacturing. 10 nm ALD films demonstrate excellent blocking capability with an insertion of only 0.03 Li per TiN formula unit exceeding 200 galvanostatic cycles at 3 µA/cm2 between 0.05 and 3 V vs. Li/Li+. An ultra-low electrical resistivity of 115 µO cm is obtained. In contrast, a partial barrier breakdown is observed for 10 nm pCVD films. High surface quality with low contamination is identified as a key factor for the excellent performance of ALD TiN. Conformal deposition of 10 nm ALD TiN in 3D structures with high aspect ratios of up to 20:1 is demonstrated. The measured capacities of the surface area enhanced samples are in good agreement with the expected values. High-temperature blocking capability is proven for a typical electrode crystallization step. Ultrathin ALD TiN is an ideal candidate as an electrically conducting Li-ion diffusion barrier for Si-integrated devices.

Lanthanum has been identified as a promising dopant to achieve ferroelectricity in HfO2 thin films in recent theoretical and experimental studies. In this work, the pyroelectric properties of 10 nm thick polycrystalline La-doped HfO2 layers manufactured by thermal atomic layer deposition are assessed employing a sinusoidal temperature profile. Compared to Si doping, La offers a broader dopant range in which ferroelectric behavior is obtained, making the material interesting for large-scale integration and deposition on area-enhanced substrates. Pyroelectric coefficients of up to −80 mC/m2 K are obtained using an optimized stoichiometry, which is comparable to earlier measurements with Si-doped HfO2 samples. Phase-sensitive evaluation of the measured current confirms the pyroelectric origin with minimal spurious contributions. The results are discussed with respect to the ferroelectric switching behavior, which is analyzed employing first-order reversal curve measurements. It is found that there is no simple linear relationship between the remanent polarization and the pyroelectric coefficient. Experimental evidence indicates that the pyroelectric response in polycrystalline thin films is modulated by internal bias fields, which can arise from charged defects. This illustrates the need for careful tuning of the manufacturing conditions and the film phase composition in future applications such as pyroelectric sensors, energy harvesting, or solid-state cooling.

Low‐grade heat sources are abundant yet challenging to use for energy harvesting. Herein, the pyroelectric effect in Si‐doped HfO2 thin films is used to demonstrate thermal‐electric energy conversion. The 20 nm thin films are grown on an area‐enhanced substrate via atomic layer deposition, which enhances the power output by a factor of 19 in comparison to planar materials. Ferroelectric and pyroelectric properties of the Si‐doped HfO2 are investigated, and a large pyroelectric coefficient of -1442 mC m−2 K−1 is measured. Wireless power distribution using an infrared laser and pyroelectric Si‐doped HfO2 receiver is demonstrated, where Brayton‐style thermodynamic cycles are used to enhance the efficiency compared with simple resistive harvesting. Thereby, energy conversion cycles at 5 Hz produce net powers of 0.75 mW cm−2. The operating conditions of the power‐beaming circuit are optimized, and the performance is found to be ultimately limited by the series resistance of the electrodes. The thermal efficiency of the HfO2‐based pyroelectric is analyzed relative to classical pyroelectrics, and the loss mechanisms are discussed.

Capacitors based on 10 nm antiferroelectric silicon-doped hafnium oxide (Si:HfO2) thin films are investigated in terms of energy storage efficiency, cycling endurance, and reliability. Atomic layer deposition (ALD) on an area-enhanced substrate with large-scale arrays of deep-trench structures is used to significantly increase the energy density, yielding a value of 450 mJ/cm2 and an energy storage efficiency of 67% at a voltage of 3 V. High breakdown fields are obtained, and the reliability measurement indicates that more than 90% of the devices survive three years when subjected to an operating voltage of 3 V. The film stoichiometry is optimized in terms of energy storage properties to achieve an antiferroelectric-like hysteresis loop with low fatigue during electric field cycling and uniform electrical characteristics throughout the 300 mm wafer. Si:HfO2 is a promising material for novel integrated energy storage applications, as it combines CMOS compatible manufacturing, high scalability, and conformal deposition using ALD.

The pyroelectric response of polycrystalline, Si-doped HfO2 layers with a thickness of 20 nm is investigated in a frequency range of 2 Hz to 20 kHz. Local Joule heating of the pyroelectric material by a deposited nickel strip is used to achieve fast thermal cycles. Over the whole frequency range, a distinct pyroelectric response is registered. A pyroelectric coefficient of −72 mC/m2K is obtained at a frequency of 10 Hz, which is in good agreement with earlier low-frequency measurements. The pyroelectric current is evaluated with respect to electric field cycling, where a successive increase is observed during wake-up. By comparing measurement results in the low- and high-frequency limit, primary and secondary pyroelectric coefficients of −53 mC/m2K and −19 mC/m2K are estimated, respectively. Si-doped HfO2 is a promising material for future energy harvesting and IR sensor applications due to environmental friendliness and CMOS compatible manufacturing.

The pyroelectric response of polycrystalline, Si-doped HfO2 layers in a thickness range of 10 nm to 50 nm is investigated employing the temperature oscillation method. The largest value of the pyroelectric coefficient is obtained for the 20 nm layer with p = 84 mC m−2 K−1, which is similar to that of lithium niobate. Furthermore, the pyroelectric coefficient is analyzed with respect to field cycling and is found to increase proportionally with the remanent polarization during wake-up, providing further evidence that the hysteresis of the material is truly ferroelectric. However, for different material thicknesses, the switchable polarization and pyroelectric coefficient are not proportional, indicating that only part of the domains is pyroelectrically active, which suggests potential for further improvement of the pyroelectric response. Due to its CMOS compatibility and conformal deposition using atomic layer deposition (ALD), Si-doped HfO2 is a promising candidate for future energy harvesting and sensor applications.

Paper presented at 5th International Conference on Defects Recognition, Imaging and Physics in Semiconductors that took place in Warsaw (Poland) during 15-19th September 2013., Compound semiconductors having high electron mobility and high injection velocity such as InGaAs are being profusely studied as possible candidates to replace Si as the channel material in highly scaled MOSFETs. One of the most critical challenges of III-V MOSFET miniaturisation lies in achieving low resistance source/drain access regions suitable for high performance logic beyond the 10nm technology node. A strong need exists to develop III-V n-type doping strategies that are capable of delivering low resistivity and low-defect ultra shallow source/drain regions with dopant concentrations above 1019 cm-3 and junction depths of Xj=5-10nm for future devices. In this work we study the Si doping characteristics of MBE grown InxGa1-xAs (x=0.17-0.33) ultra-shallow junctions (Xj¿8nm) deposited on GaAs(001) substrates under different substrate and Si effusion cell temperatures and V:III flux ratios. To this aim three in-situ doping strategies have been explored, namely homogeneous co-deposition, continuous ¿-doping and pulsed ¿-doping. The resulting Si-doping levels , determined by time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis, were found to lie between 2.7x1018cm-3 and 5.8x1019cm-3, the highest values corresponding to InGaAs junctions with triple Si ¿-layers. Elemental profiles evidence In segregation to the surface even in those samples grown at the lowest substrate temperature studied (375ºC), for which the highest Si solubility is observed. Atomic force microscopy (AFM) imaging and high-resolution transmission electron microscopy (HR-TEM) indicate an improvement in the crystal quality of the InGaAs USJs for growth temperatures above 400ºC. A characteristic self-organization of the surface into a cross hatch pattern is observed up to Si concentrations of ca. 3×1019cm-3. Above this value the InGaAs crystalline quality is degraded and the surface roughness increases significantly., Financial support under grant MAT2011-22536 is greatly acknowledged.