Temperature Dependent Current Dispersion Study in $\beta$-Ga$_2$O$_3$ FETs Using Sub-Microsecond Pulsed IV Characteristics

TL;DR

This study investigates temperature-dependent current dispersion in $eta$-Ga$_2$O$_3$ FETs, revealing trap-related effects that impact high-frequency performance and demonstrating improvements with surface passivation.

Contribution

It provides a detailed analysis of trap effects and current dispersion mechanisms in $eta$-Ga$_2$O$_3$ FETs, highlighting the role of fabrication-induced traps and passivation.

Findings

Gate lag effect causes significant current dispersion in unpassivated devices.

Surface passivation with Silicon Nitride reduces current dispersion and improves RF cutoff frequency.

Trap activation energy estimated at 99 meV, affecting device transient response.

Abstract

A comprehensive study of drain current dispersion effects in $\beta$-Ga$_2$O$_3$ FETs has been done using DC, pulsed and RF measurements. Both virtual gate effect in the gate-drain access region and interface traps under the gate are most plausible explanations for the experimentally observed pulsed current dispersion and high temperature threshold voltage shift respectively. Unpassivated devices show significant current dispersion between DC and pulsed IV response due to gate lag effect characterized by time constants in the range of 400~$\mu s$ to 600~$\mu s$. An activation energy of 99~$meV$ is estimated from temperature dependent Arrhenius plots. A variable range hopping based slow transport in conjunction with the observed shallow trap level is attributed to the observed slow transient response of drain current with respect to time. Reactive ion etching step during the device fabrication is most likely responsible for introducing the traps. Effect of traps can be minimized by using surface passivation layers, in this case, Silicon Nitride which shows significant improvement in the current dispersion and RF cutoff frequency. This work demonstrates the detrimental effect the traps can have on the current dispersion which significantly limits the high frequency operation of the device.