Full-band Monte Carlo simulation of two-dimensional electron gas in (Al$_{x}$Ga$_{1-x}$)$_{2}$O$_{3}$/Ga$_{2}$O$_{3}$ heterostructures

TL;DR

This paper presents a comprehensive full-band Monte Carlo simulation of high-field electron transport in 2DEG within (Al$_{x}$Ga$_{1-x}$)$_{2}$O$_{3}$/Ga$_{2}$O$_{3}$ heterostructures, revealing insights into velocity saturation and phonon interactions.

Contribution

It introduces a detailed simulation framework combining first-principles parameters with Monte Carlo methods for 2DEG in Ga$_{2}$O$_{3}$ heterostructures, advancing understanding of high-field transport.

Findings

Peak electron velocity increases with higher 2DEG density.

Critical field for velocity saturation remains similar to bulk values.

Antiscreening of LO phonons significantly affects low-density 2DEG transport.

Abstract

$\beta$-Gallium Oxide (Ga$_{2}$O$_{3}$) is an extensively investigated ultrawide-bandgap semiconductor for potential applications in power electronics and RF switching. The room temperature bulk electron mobility ($\sim$200 cm$^{2}$V$^{-1}$s$^{-1}$) is comparatively low and is limited by the 30 phonon modes originating from its 10-atom primitive cell. The theoretically calculated saturation velocity is 1-2$\times$10$^{7}$ cms$^{-1}$ which is comparable to GaN. The high field electron transport in the 2DEG is explored in this work based on the first principles calculated parameters. A self-consistent calculation on a given heterostructure design gives the confined eigenfunctions and eigenenergies. The intrasubband and the intersubband scattering rates are calculated based on the Fermi's golden rule considering LO phonon-plasmon screening. The high field characteristics are extracted from the full-band Monte Carlo simulation of heterostructures at 300 K. The motion of electrons in the 2DEG and the bulk is treated through an integrated Monte Carlo program which outputs the steady state zone population, transient dynamics and the velocity-field curves for a few heterostructure designs. The critical field for saturation does not change significantly from bulk values, however an improved peak velocity is calculated at a higher 2DEG density. The velocity at low 2DEG densities is impacted by the antiscreening of LO phonons which plays an important role in shaping the zone population. A comparison with the experimental measurements is also carried out and possible origins of the discrepancies with experiments is discussed.