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

We report on AlGaN/GaN heterostructures and heterostructure field-effect transistors (HFETs) fabricated on high-pressure-grown bulk GaN substrates. The $2d$ electron gas channel exhibits excellent electronic properties with room-temperature electron Hall mobility as high as $μ=1650 cm2/V s$ combined with a very large electron sheet density $ns≈1.4×1013 cm−2.$ 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 $(nsμ>2×1016 V−1 s−1)$ 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.