Poly-Ge thin-film transistors (TFTs) with Schottky source/drain (S/D) contacts were fabricated on glass by low-temperature (<500°C) processing. First, the annealing characteristics of Ni/crystal-Ge stacked structures were examined. The results indicated that NiGe∕n-Ge Schottky contacts (ϕBn=0.51eV, n=1) with flat interfaces and low reverse leakage current [(2–5)×10−2A∕cm2] could be obtained by choosing an appropriate annealing temperature (200–300°C). Based on this result, p-channel TFTs were fabricated with poly-Ge formed on glass by solid-phase crystallization at 500°C. TFTs showed relatively high hole mobility (about 140cm2∕Vs) with very low S/D parasitic resistance and no kink effect. The potential capability of the proposed devices for high-performance TFTs was demonstrated.

The state-selective dissociation dynamics for anionic and excited neutral fragments of gaseous SiCl 4 following Cl 2p and Si 2p core-level excitations were characterized by combining measurements of the photoninduced anionic dissociation, x-ray absorption and UV/visible dispersed fluorescence. The transitions of core electrons to high Rydberg states/doubly excited states in the vicinity of both Si 2p and Cl 2p ionization thresholds of gaseous SiCl 4 lead to a remarkably enhanced production of anionic, Si − and Cl − , fragments and excited neutral atomic, Si * , fragments. This enhancement via core-level excitation near the ionization threshold of gaseous SiCl 4 is explained in terms of the contributions from the Auger decay of doubly excited states, shake-modified resonant Auger decay, or/and post-collision interaction. These complementary results provide insight into the state-selective anionic and excited neutral fragmentation of gaseous molecules via core-level excitation.

We fabricated a high output power large-scale 2D addressable VCSEL array and demonstrated a small footprint transmitter (Tx) module for true solid-state LiDAR. The module integrated VCSEL array and laser diode driver built-in circuit board in three dimensions. Each used VCSEL had five junctions, large optical aperture, and bump for individual driving. The wavelength of light output through a substrate was 940 nm. VCSELs were arranged in 48×48 matrix wherein 2,304 emitters can be individually driven. The array chip was assembled on the circuit board by flip-chip bonding via bump. All VCSELs were connected to the driver with very short current path caused by the three-dimensional integration. Short current path and small current loop resulted in small resistance and inductance, which facilitated driving of VCSELs with short current pulse. The transmitter module can generate high peak power with short pulse duration for time-of-flight measurement without RF input. Each VCSEL can be sequentially driven by trigger pulse input. The footprint of the module was 17.3 mm square. We confirmed that all VCSELs emit with sequential driving mode; the peak output power was over 45 W and pulse width was approximately 4 ns. The pulse shapes and widths were nearly identical at the center and edge of the array, which is generally unusual for a Tx module with two-dimensional integration where VCSEL and laser driver are integrated side by side. The divergence of output was less than 10 °.

High-performance poly-Ge thin-film transistors (TFTs) were fabricated using NiGe Schottky contacts as source/drain (S/D). First, formation of NiGe layers by annealing of Ni/n-Ge structures was investigated as a function of annealing temperature, and NiGe/n-Ge Schottky contacts (φ Bn =0.51 eV) with a low reverse leakage current (~10 -2 A/cm 2 ) were realized at 200-300 o C. On the basis of the results, NiGe Schottky S/D contacts were fabricated using poly-Ge/quartz substrates. The TFTs showed good operation characteristics with a hole mobility of ~140 cm 2 V  1 s  1 . This is a great advantage for the realization of high-performance TFTs for future system-in-displays.

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