In the last decade, the III-N compounds have attracted much interest because of their applications in blue, violet and ultraviolet optoelectronics. Most of the devices and research use sapphire as a substrate for epitaxy of nitrides. However, these epi-structures contain a very high dislocation density induced by the 16% lattice mismatch between GaN and sapphire. In our laboratory, we grow single ...
In this paper we review the developments of producing non-polar (i.e. m-plane and a-plane) and semi-polar (i.e. (20.1)-plane) wafers by ammonothermal method. The growth method and polishing results are described. We succeeded in producing 26 mm × 26 mm non- and semi-polar wafers. These wafers possess outstanding structural and optical properties, with threading dislocation density of the order of ...
Wafer-scale arrays of well-ordered Pb(Zr0.2Ti0.8)O3 nanodiscs and nanorings were fabricated on the entire area (10 mm × 10 mm) of the SrRuO3 bottom electrode on an SrTiO3 single-crystal substrate using the laser interference lithography (LIL) process combined with pulsed laser deposition. The shape and size of the nanostructures were controlled by the amount of PZT deposited through the patterned ...
We investigated the transition energy levels of the vacancy defects in gallium nitride by means of a hybrid density functional theory approach (DFT). We show that, in contrast to predictions from a recent study on the level of purely local DFT, the inclusion of screened exchange stabilizes the triply positive charge state of the nitrogen vacancy for Fermi energies close to the valence band. On the...
A micromachined AlGaN/GaN high-electron-mobility transistor (HEMT) on a Si substrate with diamondlike carbon/titanium (DLC/Ti) heat-dissipation layers was investigated. Superior thermal conductivity and thermal expansion coefficient similar to that of GaN enabled DLC/Ti to efficiently dissipate the heat of the GaN power HEMT through the Si substrate via holes. This HEMT with DLC design also mainta...
The growth condition of thin heavily Mg-doped GaN capping layer and its effect on ohmic contact formation of p-type GaN were investigated. It is confirmed that the excessive Mg doping can effectively enhance the Ni/Au contact to p-GaN after annealing at 550 °C. When the flow rate ratio between Mg and Ga gas sources is 6.4% and the layer width is 25 nm, the capping layer grown at 850 °C exhibits th...
We report the Au-assisted chemical beam epitaxy growth of defect-free zincblende InSb nanowires. The grown InSb segments are the upper sections of InAs/InSb heterostructures on InAs(111)B substrates. We show, through HRTEM analysis, that zincblende InSb can be grown without any crystal defects such as stacking faults or twinning planes. Strain-map analysis demonstrates that the InSb segment is nea...
Highly tensile-strained sub-monolayer Ge nanostructures on GaSb have been grown by molecular beam epitaxy and studied by ultrahigh-vacuum scanning tunneling microscopy. Four different coverage rates of Ge nanostructures on GaSb are achieved and investigated. It is found the growth of Ge on GaSb follows 2D growth mode. The crystal lattice of the sub-monolayer Ge nanostructures is coherent with that...
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