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Tunnel field-effect transistors (TFETs) are a promising candidate for low-power applications owing to their steep subthreshold swing of sub-60 mV per decade. For silicon- or germanium-based TFETs, the drive current is low due to the indirect band-to-band tunneling (BTBT) process. Direct-bandgap germanium-tin (GeSn) can boost the TFET performance since phonon participation is not required during the tunneling process. Esaki diodes with negative differential resistance (NDR) are used to characterize the BTBT properties and calibrate the tunneling rates for TFET applications. This work demonstrates high-performance GeSn Esaki diodes with clear NDR at room temperature with very high peak-to-valley current ratios of 15-53 from 300 K to 4 K. A record-high peak current density of 545 kA cm

GeSn complementary metal-oxide-semiconductor (CMOS) devices have attracted much attention for future VLSI technology nodes due to high carrier mobility. However, Fermi-level pinning in metal/n-GeSn...

GeSn is a promising material for high-performance electronic and photonic devices. In this work, we present our recent achievements on high electron mobility in GeSn n-MOSFETs, an extremely low contact resistivity in metal/n-GeSn junctions, and a high tunneling current density in GeSn Esaki diodes with large peak-to-valley current ratios. Last, we present the first two-dimensional hole gas in the undoped GeSn/Ge heterostructures with strong spin-orbit coupling (SOC) effects, which is tunable by top gating.

To realize a full-scale solid-state computer, both quantum processors and classical logic controllers are suggested to be operated at cryogenic temperatures to avoid the issues of signal latency through the room-temperature controllers and the corresponding wiring complexity, and interface of quantum processors and classical controllers. While cryo-CMOS devices have been the main focus recently to address those issues, there were only few works on cryogenic memory devices published [1]. Potential candidates for cryogenic applications are based on Si MOS platforms, which would result in integration challenges with Si/SiGe [2] or Ge/GeSi [3] qubit devices. In this work, we demonstrate multi-bit cryogenic flash operations on both Si/SiGe and Ge/GeSi heterostructures for the first time at 4 K with a high endurance of > 103, long retention time of > 103 s, and a memory window of > 0.2V.

A demonstration of 2D hole gases in GeSn/Ge heterostructures with a mobility as high as 20 000 cm2 V-1 s-1 is given. Both the Shubnikov-de Haas oscillations and integer quantum Hall effect are observed, indicating high sample quality. The Rashba spin-orbit coupling (SOC) is investigated via magneto-transport. Further, a transition from weak localization to weak anti-localization is observed, which shows the tunability of the SOC strength by gating. The magneto-transport data are fitted to the Hikami-Larkin-Nagaoka formula. The phase-coherence and spin-relaxation times, as well as spin-splitting energy and Rashba coefficient of the k-cubic term, are extracted. The analysis reveals that the effects of strain and confinement potential at a high fraction of Sn suppress the Rashba SOC caused by the GeSn/Ge heterostructures.

In this work, a single-crystalline β-Ga2O3 epilayer was grown on (0001) sapphire at low temperature by low-pressure metal organic chemical vapor deposition. The optimized parameters for the chamber pressure, oxygen flow, and growth temperature were 15 Torr, 200 sccm, and 500 °C, respectively. The β-Ga2O3 epilayer was fabricated as a metal-semiconductor-metal solar-blind deep ultraviolet photodetector. Due to the gallium oxide grown at low temperature, the as-grown β-Ga2O3 epilayer was annealed at 800 °C in atmosphere or in a nitrogen environment. The effects of defects of the β-Ga2O3 epilayer before and after N2 annealing were studied using x-ray diffraction system, cathodoluminescence at differential temperature, and Hall measurement. The β-Ga2O3 epilayer that was N2 annealed for 15 min presented better photodetector performance than the as-grown β-Ga2O3 epilayer. The annealed epilayer exhibited a dark current of 1.6 × 10−13 A under 5 V bias.