Cd acceptors in $Ga_2O_3$, an atomistic view

TL;DR

This study demonstrates the successful incorporation of Cd as an acceptor in $eta$-$Ga_2O_3$, revealing atomic-scale behavior and charge states, which could advance p-type doping strategies for wide bandgap semiconductors.

Contribution

It introduces a combined experimental and computational approach to characterize Cd doping in $eta$-$Ga_2O_3$, providing new insights into its acceptor behavior and atomic-scale properties.

Findings

Cd acts as an acceptor sitting in octahedral Ga sites

No polaron deformations or nearby point defects observed

Thermally activated electrons with an activation energy of 0.54 eV

Abstract

Finding suitable p-type dopants, as well as reliable doping and characterization methods for the emerging wide bandgap semiconductor $\beta$-$Ga_2O_3$ could strongly influence and contribute to the development of the next generation of power electronic. In this work, we combine easily accessible ion implantation, diffusion and nuclear transmutation methods to properly incorporate the Cd dopant into the $\beta$-$Ga_2O_3$ lattice, being subsequently characterized at the atomic scale with the Perturbed Angular Correlation (PAC) technique and Density Functional Theory (DFT) simulations. The acceptor character of Cd in $\beta$-$Ga_2O_3$ is demonstrated, with Cd sitting in the octahedral Ga site in the negative charge state, showing no evidence of polaron deformations nor extra point defects nearby. Furthermore, thermally activated free electrons were observed for temperatures above ~648 K with an activation energy of 0.54(1) eV. At lower temperatures the local electron transport is dominated by a tunneling process between defect levels and the Cd probe.