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We demonstrate selectively-grown GaAs nano/micro structures on silicon substrates by molecular beam epitaxy. Hexagonal or rectangular shaped GaAs crystals, depending on the orientation of the silicon substrate, were formed inside the silicon-dioxide-masked nanoholes at 630°C. Clear facets, which are the low-energy {011} planes, indicate single-crystalline nature of the growth. GaAs/InAs/GaAs structure...
The spectral photoresponse characteristics for visible blind GaN/AlGaN p-i-n photodiode have been numerically studied. Effects of the absorption layer thickness and the n-layer thickness on the photoresponse spectra have been investigated. Our work shows that the absorption layer thickness and n-layer thickness have important impact on the peak value of photoresponse spectra and rejection ratio of...
III-V FETs are being developed for potential application in 0.3-3 THz systems and VLSI. To increase bandwidth, we must increase the drive current Id = qnsvinjWg per unit gate width Wg, requiring both high sheet carrier concentrations ns and high injection velocities vinj. Present III-V NFETs restrict control region transport to the single isotropic Γ band minimum. As the gate dielectric is thinned,...
III-V FETs are in development for both THz and VLSI applications. In VLSI, high drive currents are sought at low gate drive voltages, while in THz circuits, high cutoff frequencies are required. In both cases, source and drain access resistivities must be decreased, and transconductance and drain current per unit gate width must be increased by reducing the gate dielectric thickness, reducing the...
The structure of amorphous compound semiconductor has been constructed successfully by ldquocontinuous random networksrdquo (CRN). Based on the first-principles calculations, the effects of different local disorder on density of states are studied in detail. The results show that the wrong bonds mainly have effect on the deeper energy band and introduce new electron states, and the dangling bonds...
We report on 2D simulations of dark current for GaN/GaN/Al0.33Ga0.67N p-i-n photodiode. The simulated result is in good agreement with experiment data indicating that avalanche multiplication is the cause of breakdown and band-to-band tunneling is the main source of dark current before breakdown. Effects of interface charge on avalanche current are investigated in detail.
Scanning thermal microscope (SThM) and electron backscatter diffraction (EBSD) techniques were used to investigate the local thermal-conductivity of a GaN-buffer-sapphire heterostructure. Compared with GaN epilayer, buffer layer displayed the low thermal-conductivity and the high strain state due to the lattice distortion.
The AlInGaN-based high electron mobility transistor (HEMT) has proven to be the leading candidate for simultaneously realizing ultra-high frequency and ultra-high power amplifiers. The potential for these devices extends into operation in the mm-wave regime. Processes and device technologies that have resulted in these tremendous improvements are addressed
We report lateral quantum coupling between two self-assembled InGaAs/GaAs quantum dots. Single-photon photoluminescence emission has been observed from this quantum dot molecule and the level of coupling can be controlled using a static electric field.
Operation of AlGaN/GaN HFETs in space was simulated by irradiation with protons and heavy ions at 68 MeV and 2MeV and fluences up to 1013 cm-2. Before and after irradiation dc and pulsed I-V characteristics of the AlGaN HFET devices were measured. A thick GaN reference layer was characterized by photoluminescence, X-ray diffraction and Hall measurements before and after irradiation. The results of...
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