Influence of dislocations in the GaN layer on the electrical properties of an AlGaN/GaN heterostructure

This paper reports on a comparative study of the spatialdistributions of the electrical, optical, and structural propertiesin an AlGaN/GaN heterostructure. Edge dislocation density in the GaNtemplate layer is shown to decrease in the regions of the waferwhere the heterostructure sheet resistance increases and the GaNphotoluminescence band-edge energy peak shifts to a high wavelength.This phenomenon is found to be attributed to the local compressivestrain surrounding edge dislocation, which will generate a localpiezoelectric polarization field in the GaN layer in the oppositedirection to the piezoelectric polarization field in the AlGaN layer andthus help to increase the two-dimensional electron gasconcentration.