GaN-AlGaN heterostructure field-effect transistors over bulk GaN substrates

We report on AlGaN/GaN heterostructures and heterostructure field-effect tr ansistors (HFETs) fabricated on high-pressure-grown bulk GaN substrates. Th e 2d electron gas channel exhibits excellent electronic properties with roo m-temperature electron Hall mobility as high as mu = 1650 cm(2)/V s combine d with a very large electron sheet density n(s) approximate to 1.4 x 10(13) cm(-2). The HFET devices demonstrated better linearity of transconductance and low gate leakage, especially at elevated temperatures. We also present the comparative study of high-current AlGaN/GaN HFETs (n(s)mu > 2 x 10(16) V-1 s(-1)) grown on bulk GaN, sapphire, and SiC substrates under the same conditions. We demonstrate that in the high-power regime, the self-heating effects, and not a dislocation density, is the dominant factor determining the device behavior. (C) 2000 American Institute of Physics. [S0003-6951(00 )02425-6].