Effect of C- and Fe-doped GaN buffer on AlGaN/GaN high electron mobility transistor performance on GaN substrate using side-gate modulation

Abstract

Side-gate (SG) modulation on AlGaN/GaN high electron mobility transistor performance with C-doped GaN buffer (C-GaN) and Fe-doped GaN buffer (Fe-GaN) layer on GaN substrate is experimentally investigated. The SG contacts are located 6 μm from either side of the device mesa, and etched near the channel layer. SG modulation is done by two methods, that is, applying a fixed side-gate voltage (V_SG) bias while the DC characteristics are measured, and bidirectional dual sweeping the applied V_SG while measuring the on-state drain current (I_D). At fixed high negative V_SG, a drastic decrease in transconductance and I_D is evident for C-GaN as compared to Fe-GaN. Moreover, evidence of larger memory effect in C-GaN, is demonstrated as shown in the I_D hysteresis feature using bidirectional dual-sweep V_SG measurements. The I_D decreased at high negative V_SG is inferred to be due to the field modulation caused by the SG.