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 1 kV they resolve individual threading dislocations on the sample surface at low temperature (5 K), 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 5 K, an exciton diffusion length of 62±28 nm was found for GaN:Si (-3x10 18 cm−3) compared with 81±20 nm for a nominally undoped n-type GaN (-1x10 16 cm−3).