High indium content InGaN films were grown on sapphire substrate using low temperature pulsed laser deposition (PLD)
with nitrogen plasma and a specific target. The controllable target consists of two separate sections: an indium sheet with
periodic rectangular-holes and a standard GaN wafer. By changing the rectangular-hole area, a modulated indium vapor
was excited by pulsed laser and introduced into the InGaN deposition reaction, contributing the increase in the
incorporation of indium into the InGaN film. The structural and optical stability of the 33 and 60% indium InGaN
revealed no differences in the line-shape and peak position even after annealing at 800°C for 75 min from x-ray
diffraction and luminescence results. Moreover, such high thermal stability of 60% InGaN film was put in metal organic
chemical vapor deposition (MOCVD) to regrow GaN layer, the peak position of 860 nm remained unchanged after
MOCVD regrowth. The flat and uniform of regrown sample indicates that the PLD method used in this study is indeed
promising for the development long wavelength of high indium content InGaN emitters.
High indium composition InGaN films were co-deposited on u-GaN templates using low temperature (300°C)
pulsed laser deposition (PLD). The du-composition target consisted of a 3-inch indium sheet drilled with periodic
rectangular holes mounted on a normal GaN wafer. By changing the ratio of the holes areas to total sheet area, the
indium concentration in two InGaN films was set to 33% and 60%. The structural and optical characteristics of these
films are investigated through isochronal and isothermal annealing. X-ray diffraction (XRD) and cathodeluminescence
results for the 33% sample exhibited no significant differences in line-shape and peak position even after annealing at
800°C for 100 minutes. In contrast, the XRD peak of 60% sample became broadened under the same annealing condition.
This slight inhomogeneity in composition also resulted in two visible peaks in the photoluminescence spectrum.
Although the optical properties of the 60% sample can be considered merely acceptable, the advantages of applying PLD
to the growth of high thermal stability and high indium composition InGaN have been made clear. The PLD technique
shows promise for developing long wavelength devices.
The β-Ga2O3 films were grown on (0001) sapphire at 500 °C by metal organic chemical vapor deposition. In the
analysis of crystal structure, we found that the (-201) oriented single crystal β-Ga2O3 epilayer can be obtained under low
chamber pressure of 15 torr. Moreover, a metal-semiconductor-metal solar-blind deep ultraviolet photodetector was
fabricated with the β-Ga2O3 epilayer. As the bias voltage is 5 V, the photodetector exhibits a relatively low dark current
about 0.2 pA, which induced by the highly resistive nature of the β-Ga2O3 thin films. From the responsivity result, it can
be observed that photodetector shows a maximum responsivity at 260 nm, revealing the β-Ga2O3 photodetector was
really solar-blind. The responsivity of the photodetector was as high as 20.1 A/W with an applied bias of 5 V and an
incident light wavelength of 260 nm. The improved performance is attributed to the high quality of β-Ga2O3 epilayer.