Donors and Deep Acceptors in $\beta$-Ga2O3

TL;DR

This study investigates the electrical properties of various dopants in $eta$-Ga2O3, determining donor and acceptor energy levels and confirming the shallow nature of Si and Ge donors through temperature-dependent Hall measurements.

Contribution

It provides precise estimates of donor and acceptor energy levels in $eta$-Ga2O3 using self-consistent fitting of temperature-dependent data across multiple growth methods.

Findings

Si and Ge are confirmed as shallow donors with 30 meV energy levels.

Fe acts as a deep acceptor with an energy of 860 meV.

Mg exhibits an activation energy of 1.1 eV in $eta$-Ga2O3.

Abstract

We have studied the properties of Si, Ge shallow donors and Fe, Mg deep acceptors in $\beta$-Ga2O3 through temperature dependent van der Pauw and Hall effect measurements of samples grown by a variety of methods, including edge-defined film-fed (EFG), Czochralski (CZ), molecular beam epitaxy (MBE), and low pressure chemical vapor deposition (LPCVD). Through simultaneous, self-consistent fitting of the temperature dependent carrier density and mobility, we are able to accurately estimate the donor energy of Si and Ge to be 30 meV in $\beta$-Ga2O3. Additionally, we show that our measured Hall effect data are consistent with Si and Ge acting as typical shallow donors, rather than shallow DX centers. High temperature Hall effect measurement of Fe doped $\beta$-Ga2O3 indicates that the material remains weakly n-type even with the Fe doping, with an acceptor energy of 860 meV relative to the conduction band for the Fe deep acceptor. Van der Pauw measurements of Mg doped Ga2O3 indicate an activation energy of 1.1 eV, as determined from the temperature dependent conductivity.