The influence of OMVPE growth pressure on the morphology, compensation, and doping of GaN and related alloys |
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Authors: | A E Wickenden D D Koleske R L Henry R J Gorman M E Twigg M Fatemi J A Freitas Jr W J Moore |
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Affiliation: | (1) Electronics Science and Technology Division, Code 6800, Naval Research Laboratory, 20375-5320 Washington, D.C. |
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Abstract: | Growth pressure has a dramatic influence on the grain size, transport characteristics, optical recombination processes, and
alloy composition of GaN and AlGaN films. We report on systematic studies which have been performed in a close spaced showerhead
reactor and a vertical quartz tube reactor, which demonstrate increased grain size with increased growth pressure. Data suggesting
the compensating nature of grain boundaries in GaN films is presented, and the impact of grain size on high mobility silicon-doped
GaN and highly resistive unintentionally doped GaN films is discussed. We detail the influence of pressure on AlGaN film growth,
and show how AlGaN must be grown at pressures which are lower than those used for the growth of optimized GaN films. By controlling
growth pressure, we have grown high electron mobility transistor (HEMT) device structures having highly resistive (105 Ω-cm) isolation layers, room temperature sheet carrier concentrations of 1.2×1013 cm−2 and mobilities of 1500 cm2/Vs, and reduced trapping effects in fabricated devices. |
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Keywords: | GaN epitaxy pressure grain size transport MOCVD TEM PL |
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