Controlling a three dimensional electron slab of graded Al$_{x}$Ga$_{1-x}$N

TL;DR

This paper demonstrates polarization-induced doping in graded AlGaN layers grown by MOCVD, creating a three-dimensional electron slab with tunable conductivity confirmed by various characterization techniques.

Contribution

It introduces a method to achieve high electron concentrations in graded AlGaN layers via polarization doping, with detailed structural and electronic characterization.

Findings

Achieved electron concentrations up to 10^20 cm^-3

Confirmed composition gradient with high-resolution techniques

Demonstrated tunable conductivity of the 3D electron slab

Abstract

Polarization induced degenerate $n$-type doping with electron concentrations up to $\sim$10$^{20}$\,cm$^{-3}$ is achieved in graded Al$_{x}$Ga$_{1-x}$N layers ($x$: 0\%$\rightarrow$37\%) grown on unintentionally doped and on $n$-doped GaN:Si buffer/reservoir layers by metal organic vapor phase epitaxy. High resolution x-ray diffraction, transmission electron microscopy and electron energy loss spectroscopy confirm the gradient in the composition of the Al$_{x}$Ga$_{1-x}$N layers, while magnetotransport studies reveal the formation of a three dimensional electron slab, whose conductivity can be adjusted through the GaN(:Si) buffer/reservoir.