Abstract
In this Letter, we experimentally investigate the impact of gate geometry on forward operation of Schottky-gate p-GaN high electron mobility transistors (HEMTs). In particular, we analyze devices with changing gate-metal/p-GaN junction area and p-GaN/AlGaN/GaN heterostructure area in the linear regime. These devices exhibit unique threshold voltage and subthreshold swing scaling dependence with gate geometry that is in contrast with classic field-effect transistors. On the other hand, peak transconductance and ON resistance are found to scale classically. We find that these results arise from the fact that with a Schottky contact to the p-GaN layer, under steady-state conditions, the p-GaN layer voltage is set by current continuity across the gate stack. Furthermore, a detailed scaling study of the gate current reveals that current flow across the p-GaN/AlGaN/GaN heterostructure is not uniform—instead, it preferentially flows through the ungated portion of the p-GaN layer. Our study concludes that in Schottky-type p-GaN gate HEMTs, the respective areas of two junctions constitute an additional design degree of freedom to fine-tune device performance.
Highlights
In this Letter, we study p-GaN high electron mobility transistors (HEMTs) with different gate geometries
In this Letter, we experimentally investigate the impact of gate geometry on forward operation of Schottky-gate p-GaN high electron mobility transistors (HEMTs)
Peak transconductance and ON resistance are found to scale classically. We find that these results arise from the fact that with a Schottky contact to the p-GaN layer, under steady-state conditions, the p-GaN layer voltage is set by current continuity across the gate stack
Summary
In this Letter, we study p-GaN HEMTs with different gate geometries. We find unusual dependences of device figures of merit— threshold voltage and subthreshold swing—on gate geometry. These devices exhibit unique threshold voltage and subthreshold swing scaling dependence with gate geometry that is in contrast with classic field-effect transistors.
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