AlGaN/GaN HEMTs on free-standing GaN substrates MBE growth and microwave characterization
We investigate the role of substrate temperature and gallium flux on the DC and microwave properties of AlGaN/GaN high electron mobility transistors grown by molecular-beam epitaxy on free standing, hydride vapor phase epitaxy grown GaN substrates. The freestanding substrates have threading dislocation densities below 10(7) cm(-2). We find that AlGaN/GaN heterostructures with excellent properties may be grown within a wide range of substrate temperatures and fluxes. Electron Hall mobilities above 1700 cm(2)/V s and sheet resistances below 370 ohm/square are typical. We are able to obtain high saturated drain currents with low gate leakage. Off-state breakdown voltages as high as 200 V with low drain and gate leakage currents have been measured. Further, we have measured microwave output power densities above 5 W/mm at 4 GHz with a power-added efficiency of 46% and an associated gain of 13.4 dB. We attribute improved electrical properties in these devices to the reduced threading dislocation density compared to those grown on non-native substrates. (c) 2006 Elsevier B.V. All rights reserved.
Storm, D. F., Katzer, D. S., Roussos, J. A., Mittereder, J. A., Bass, R., Binari, S. C., ... Evans, K. R. (2007). AlGaN/GaN HEMTs on free-standing GaN substrates: MBE growth and microwave characterization. Journal of Crystal Growth, 301, 429-433. DOI: 10.1016/j.jcrysgro.2006.11.085