In this paper, a patterned sacrificial layer structure comprised of 3 mu m-wide SiO(2) narrow strips and 3 mu m spacing between strips fabricated on sapphire substrate was proposed. The structure was used not only to improve GaN epilayer quality, but also as a sacrificial layer structure. The GaN light emitting diodes (LEDs) covered by the Cu substrate was fabricated after the GaN epitaxy layer was grown on the sapphire by lateral epitaxial overgrowth. Chemical etching using hydrofluoric acid was conducted to remove the aforementioned SiO(2) strips, and hence transform them into narrow tunnels. The GaN LEDs with the Cu substrate detached from the sapphire substrate after interface strain was increased, which demonstrates that n-side-up vertical GaN LEDs could be more easily obtained using chemical lift-off technology without laser damage compared with the laser lift-off technique. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3582352] All rights reserved
This work presents dc characteristics (gain and leakage current) of a GaN/InGaN/ZnO npn collector-up heterojunction bipolar transistor (HBT) measured at 300, 200, and 100 K. The GaN-based epilayers of HBT were grown by metallorganic chemical vapor deposition, and the n-ZnO film was then deposited on top of p-InGaN by sputtering. X-ray diffraction analysis demonstrates that annealing at
600°C
for 60 s in ambient
normalN2
improved the quality of the ZnO film. Moreover, this study shows that the current gains
(β)
from the Gummel plot increased as the temperature decreased because the leakage current of the collector current
(InormalC)
is not a strong function of temperature. However, gains
(GCE)
from the measured common-emitter current–voltage characteristics increased slightly as the temperature decreased due to a reduction in the recombination current coupled with lower injection efficiency. These preliminary results show the potential of fabricating GaN/InGaN/ZnO HBTs without dry etching to reach the p-GaN layer, as required in the emitter-up geometry.
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