X-ray diffraction peak profiles from threading dislocations in GaN epitaxial films

TL;DR

This paper investigates the x-ray diffraction peak profiles of GaN epitaxial films with high threading dislocation densities, revealing Gaussian cores and power-law tails, and provides a method to quantify dislocation densities and correlations.

Contribution

It introduces a model fitting the entire diffraction profile of GaN films with dislocations, enabling extraction of dislocation densities and correlation ranges.

Findings

Peak profiles have Gaussian centers with power-law tails.

The $q^{-3}$ decay confirms random dislocation behavior.

Densities of edge and screw dislocations are quantified.

Abstract

We analyze the lineshape of x-ray diffraction profiles of GaN epitaxial layers with large densities of randomly distributed threading dislocations. The peaks are Gaussian only in the central, most intense part of the peak, while the tails obey a power law. The $q^{-3}$ decay typical for random dislocations is observed in double-crystal rocking curves. The entire profile is well fitted by a restricted random dislocation distribution. The densities of both edge and screw threading dislocations and the ranges of dislocation correlations are obtained.