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GaAs-based p-i-n 850 nm infrared photodetectors with a narrow bandpass characteristic were successfully fabricated and demonstrated by epitaxial growth technology. The photo to dark current ratios of the fabricated PDs were $1.76\times10$ 7 and $2.08\times10$ 3 at 0 and −5 V, respectively. It can be seen clearly that our fabricated PDs can achieve a very steeply and rapidly falling cut-off bandpass characteristic by inserting a p-Al0.1Ga0.9As filter layer. The full width at half maximum of the photo response was only 65.9 nm. Then, the peak responsivity value of the fabricated PDs occurred at 855 nm was 0.49 A/W with a quantum efficiency of 71.2% at −1 V. Moreover, the low frequency noise of the fabricated PDs was dominated by 1/f-type noise. And, the best detectivity was calculated to be $1.17\times10$ 13 cmHz0.5W−1 at a bias voltage of 0 V.

GaN metal-semiconductor–metal (MSM) ultraviolet photodetectors (PDs) with ex situ sputtered AlN nucleation layer were investigated and demonstrated. The crystal quality, electrical, and optical properties of GaN PDs were improved using ex situ sputtered AlN nucleation layer. Compared with in situ AlN nucleation layer, it was found that the X-ray rock curve widths and yellow or blue bands of cathodoluminescence spectra of the PDs prepared by ex situ sputtered AlN nucleation layer were significantly reduced and smaller due to the improved crystal quality. It was also found that the dark current and responsivity of PDs with ex situ sputtered AlN nucleation layer were more effectively reduced and enhanced. Moreover, GaN MSM PDs with ex situ sputtered AlN nucleation layer could achieve the higher quantum efficiency and detectivity.

Gate-all-around (GAA) poly-Si thin-film transistors (TFTs) with multiple nanowire channels has better performance compared with planar TFT, such as lower threshold voltage VTH, smaller subthreshold swing (SS), lower minimum current I OFF, higher maximum on/off current ratio ION/IOFF, and higher mobility. However, each nanowire has three sharp corners to obtain high local electric fields under gate bias stresses, such that GAA TFT inherently suffers from an inevitable reliability problem. The local electric fields accelerate the degradation of VTH and SS. The VTH degradation under negative gate bias stress is related to the released electron trapping in stressed gate oxide during diffusion-controlled electrochemical reaction. For GAA TFT, minimum IOFF and ION/IOFF ratio still maintain better characteristics due to smaller channel body. Moreover, the obvious retardation in mobility degradation was obtained for GAA TFT because the hydrogen atoms can effectively rearrange the tail states located near the band edge in the channel during gate bias stresses.

Indium-tin-oxide/homoepitaxial ZnSe/indium-tin-oxide metal-semiconductor-metal ultraviolet/blue sensors were prepared on the ZnSe substrates. It was found that the Schottky-barrier height became larger and the interface state density became smaller after annealing. With an incident wavelength of 448 nm and an applied bias of 1 V, it was found that the responsivities for the sensors with and without thermal annealing were 0.15 and 0.12 A/W, which corresponds to the quantum efficiencies of 40% and 33.5%, respectively. Furthermore, it was found that the sensors with a smaller noise equivalent power and larger detectivity can be achieved by annealing

The optical property and electrostatic discharge (ESD) endurance of GaN-based light-emitting diodes (LEDs) with varied undoped GaN thickness are studied and demonstrated. As the undoped GaN thickness increased, the generation of V-shaped defects in the active region was suppressed. Therefore, the output power for a 6-μ.m-thick undoped GaN layer would be enhanced remarkably due to the reduction of nonradiative recombination ratio within the active region. On the other hand, under a reverse ESD pulse voltage of 5.5 kV, the survival rate of the LEDs with an undoped GaN layer thickness of 1.5, 4, and 6 μm were 75%, 65%, and 55%, respectively. It was found that the ESD endurance for a 1.5-μ.m-thick undoped GaN layer with higher internal capacitance was obviously better than others. This could be related to the built-in electric field of LEDs induced by spontaneous polarization field.

The crystal quality, electrical, and optical characteristics of GaN-based light-emitting diodes (LEDs) were improved using a sputtered AlN nucleation layer. Replacing the in situ AlN nucleation layer with the sputtered AlN nucleation layer reduced the (002) and (102) X-ray rocking curve widths of the GaN layer from 318.0 to 201.1 and 412.5 to 225.0 arcsec, respectively. The -20-V reverse leakage current of the LEDs with the sputtered AlN nucleation layer is about three orders less than that of the LEDs with the in situ AlN nucleation layer. In addition, the LEDs with sputtered AlN nucleation layer could sustain more than 60% passing yield on the ESD test of under a -600-V machine mode, whereas the LEDs with the in situ AlN nucleation layer sustained less than 40% passing yield. Moreover, the 20-mA output power of the LEDs with the sputtered AlN nucleation layer also improved by approximately 5.73% compared with that of the LEDs with the in situ AlN nucleation layer.