Investigation of RF performance of Ku-band GaN HEMT device and an in-depth analysis of short channel effects

TL;DR

This study investigates how short gate lengths in AlGaN/GaN HEMTs affect RF performance and short channel effects, including temperature dependence, and explores gate engineering solutions to mitigate these effects.

Contribution

It provides the first detailed analysis of temperature-dependent short channel effects in GaN HEMTs and demonstrates that recessed gate structures can effectively reduce these effects.

Findings

Short gate length significantly impacts small signal parameters and linearity.

Temperature influences the severity of short channel effects in GaN HEMTs.

Recessed gate structures improve RF performance by mitigating short channel effects.

Abstract

In this paper, we have characterized an AlGaN/GaN High Electron Mobility Transistor (HEMT) with a short gate length (Lg $\approx$ 0.15$\mu$m). We have studied the effect of short gate length on the small signal parameters, linearity parameters and gm-gd ratio in GaN HEMT devices. To understand how scaling results in the variation of the above-mentioned parameters a comparative study with higher gate length devices on similar heterostructure is also presented here. We have scaled down the gate length but the barrier thickness(t$_{bar}$) remained same which affects the aspect ratio (L$_{g}$/t$_{bar}$) of the device and its inseparable consequences are the prominent short channel effects (SCEs) barring the optimum output performance of the device. These interesting phenomena were studied in detail and explored over a temperature range of -40$^\circ$C to 80$^\circ$C. To the best of our knowledge this paper explores temperature dependence of SCEs of GaN HEMT for the first time. With an approach to reduce the impact of SCEs a simulation study in Silvaco TCAD was carried out and it is observed that a recessed gate structure on conventional heterostructure successfully reduces SCEs and improves RF performance of the device. This work gives an overall view of gate length scaling on conventional AlGaN/GaN HEMTs.