Extended Data Fig. 8: Back-gating effect of N-polar HEMT.
From: Using both faces of polar semiconductor wafers for functional devices
a,b, Log scale (a) and linear scale (b) transfer curves of a three-terminal N-polar HEMT gated by the substrate contact made with indium as shown in Extended Data Fig. 1, with the top gate left floating. Each curve represents the dependency of the drain (solid) and gate (dashed) current as a function of the back-gate voltage (VBS), with a fixed drain bias. Drain bias increases from 0.5 V to 5.0 V at a 0.5-V step in the direction the arrow points, with the last curve taken at a drain bias (VDS) of 0.2 V. c, Output characteristics of a back-gated N-polar HEMT. The maximum drain current is comparable with the value measured on the top-gated HEMT. For VBS − VDS ≲ −4 V, the drain current is dominated by the high gate leakage current. d, Log-scale transfer curves of a four-terminal N-polar HEMT measurement with fixed VBS and VDS. The blue curve represents the transfer curve with a back gate. No drain current modulation is observed for VDS − VBS ≈ 5 V and up to six orders of drain current modulation is observed for VDS − VBS = 0 V.
