Carrier recombination near threading dislocations in GaN epilayers by low voltage cathodoluminescence

Abstract

The authors present a low voltage cathodoluminescence (CL) study of as grown GaN and GaN:Si epilayers on sapphire. At 1kV they resolve individual threading dislocations on the sample surface at low temperature (5K), which appear as correlated dark spots. Analysis of CL intensity profiles across individual dislocation cores provides a direct measurement of the exciton and minority carrier diffusion lengths. Using this approach at 5K, an exciton diffusion length of 62±28nm was found for GaN:Si (∼3×1018cm−3) compared with 81±20nm for a nominally undoped n-type GaN (∼1×1016cm−3).