S. B. Wang

A High-Responsivity GaN Nanowire UV Photodetector

The authors report the conversion of β-Ga2O3 nanowires (NWs) to GaN NWs through ammonification and the fabrication of a GaN NW photodetector (PD). Compared with conventional 2-D GaN PDs, it was found that we could achieve a 1000 times larger photocurrent from the GaN NW PD. It was also found that dynamic response of the GaN NW PD was stable and reproducible with an on/off current contrast ratio of around 1000. Furthermore, it was found that UV-to-visible rejection ratio observed from the GaN NW PD was also larger, as compared to conventional 2-D GaN PDs.

ZnSe Nanowire Photodetector Prepared on Oxidized Silicon Substrate by Molecular-Beam Epitaxy

We reported the growth of ZnSe nanowires on oxidized Si substrate by molecular-beam epitaxy. It was found that average length, average diameter, and density of the ZnSe nanowires were 1.2 μm, 48 nm, and 1.04 X 10 7 cm -2 , respectively. It was also found that the ZnSe nanowires were structurally uniform and defect-free with a pure zinc blend structure. UV photodetectors were then fabricated by sputtering a thick Au film through an interdigitated shadow mask onto the ZnSe nanowires. It was found that photocurrent to dark current contrast ratio of our ZnSe nanowire photodetector was >90 with 0.1 V applied bias.

A Quaternary ZnCdSeTe Nanotip Photodetector

The authors report the growth of needle-like high density quaternary Zn0.87Cd0.13Se0.98Te0.02nanotips on oxidized Si(100) substrate. It was found that average length and average diameter of the nanotips were 1.3 μm and 91 nm, respectively. It was also found that the as-grown ZnCdSeTe nanotips exhibit mixture of cubic zinc-blende and hexagonal wurtzite structures. Furthermore, it was found that the operation speeds of the fabricated ZnCdSeTe nanotip photodetector were fast with turn-on and turn-off time constants both less than 2 s.

ZnSe/ZnSeTe Superlattice Nanotips

The authors report the growth of ZnSe/ZnSeTe superlattice nanotips on oxidized Si(100) substrate. It was found the nanotips exhibit mixture of cubic zinc-blende and hexagonal wurtzite structures. It was also found that photoluminescence intensities observed from the ZnSe/ZnSeTe superlattice nanotips were much larger than that observed from the homogeneous ZnSeTe nanotips. Furthermore, it was found that activation energies for the ZnSe/ZnSeTe superlattice nanotips with well widths of 16, 20, and 24 nm were 76, 46, and 19 meV, respectively.

InN nanorods prepared with CrN nanoislands by plasma-assisted molecular beam epitaxy

The authors report the influence of CrN nanoisland inserted on growth of baseball-bat InN nanorods by plasma-assisted molecular beam epitaxy under In-rich conditions. By inserting CrN nanoislands between AlN nucleation layer and the Si (111) substrate, it was found that we could reduce strain form Si by inserting CrN nanoisland, FWHM of the x-ray rocking curve measured from InN nanorods from 3,299 reduced to 2,115 arcsec. It is due to the larger strain from lattice miss-match of the film-like InN structure; however, the strain from lattice miss-match was obvious reduced owing to CrN nanoisland inserted. The TEM images confirmed the CrN structures and In droplets dissociation from InN, by these results, we can speculate the growth mechanism of baseball-bat-like InN nanorods.

Low-Frequency Noise Characteristics of GaN Schottky Barrier Photodetectors Prepared With Nickel Annealing

In this paper, GaN Schottky barrier photodetectors (PDs) prepared with and without Ni treatment were fabricated. I-V and noise characteristics of these devices were then investigated. Comparing the GaN PDs with and without Ni treatment, it was found that GaN PDs prepared with Ni treatment can not only reduce dark current, but also enhance the UV-to-Vis rejection ratio. With an applied bias of -2 V, it was found that noise equivalent power (NEP) and detectivity (D*) for the PDs prepared without Ni treatment were 9.95 × 10^-8 W and 1.59 × 10⁷ cmHz^0.5W^-1, respectively. At the same applied bias, it was also found that NEP and D* for PDs prepared with Ni treatment were 1.74 × 10^-11 W and 9.07 × 10¹⁰ cmHz^0.5W^-1, respectively.

Growth and Photoelectric Properties of Twinned ZnSe Te Nanotips

The authors report the growth of high density ZnSe0 .9 Te 0 .1 nanotips by molecular beam epitaxy and the fab- rication of ZnSeTe nanotip photodetector. It was found that the as-grown ZnSe0 .9 Te 0 .1 nanotips were twinned with alternative multidomains and mixture of cubic zinc-blende/hexagonal wurtzite phases. With 5-V applied bias, it was found that photocurrent to dark current contrast ratio of the fabricated photodetector was larger than 700.

Growth of ZnSe[sub 1−x]Te[sub x] Nanotips and the Fabrication of ZnSe[sub 1−x]Te[sub x] Nanotip-Based Photodetector

We reported the growth of high density ternary ZnSeTe nanotips on oxidized Si(100) substrate and the fabrication of the ZnSeTe nanotip-based photodetector. The as-grown ZnSeTe nanotips exhibited a mixture of cubic zinc blende and hexagonal wurtzite structures. The average length of the ZnSeTe nanotips was 0.9 μm. With 5% Te incorporation, the 20 K photoluminescence peak redshifted by 27 nm. Furthermore, a photocurrent to dark current contrast ratio was larger than 40 for the fabricated photodetector.

ZnSe/ZnCdSeTe Superlattice Nanotips

The authors report the growth of quaternary ZnCdSeTe nanotips and ZnSe/ZnCdSeTe superlattice nanotips on oxidized Si(1 0 0) substrate. It was found that the nanotips exhibit mixture of cubic zinc-blende and hexagonal wurtzite structures. It was also found that photoluminescence intensities observed from the ZnSe/ZnCdSeTe superlattice nanotips were much larger than that observed from the homogeneous ZnCdSeTe nanotips. Furthermore, it was found that activation energies for the ZnSe/ZnCdSeTe superlattice nanotips with well widths of 12, 16, 20, and 24 nm were 189, 205, 292, and 240 meV, respectively.

Growth and photoelectric properties of twinned ZnSe1

The authors report the growth of high density ZnSe0 .9 Te 0 .1 nanotips by molecular beam epitaxy and the fab- rication of ZnSeTe nanotip photodetector. It was found that the as-grown ZnSe0 .9 Te 0 .1 nanotips were twinned with alternative multidomains and mixture of cubic zinc-blende/hexagonal wurtzite phases. With 5-V applied bias, it was found that photocurrent to dark current contrast ratio of the fabricated photodetector was larger than 700.