Photoluminescence microscopy investigation of lattice defects in epitaxial heterostructures

Spectrally selective photoluminescence microscopy has been used to investigate non-radiative defects and crystal imperfections in lattice-matched AlGaAs/GaAs quantum well structures grown by metalorganic vapour phase epitaxy and molecular beam epitaxy. Defects are selectively imaged in different epilayers of the heterostructures, using the compositional dependence of the luminescence wavelengths LambdasubPL. The correlation of LambdasubPL with individual layers allows one to analyse generation, propagation and blocking of defects during epitaxial growth, thereby discriminating growth-induced defects against imperfections caused by substrate imperfections. The propagation and gradual modification of defects from the bottom to the top of a sequence of layers are clearly observed. The influence of GaAs buffer layers, short period superlattices and AlGaAs barrier layers on the quality of subsequently deposited layers will be demonstrated.