In-situ determination of interface roughness in MOVPE-grown visible VCSELs by reflectance spectroscopy

Abstract

This paper reports on an in-situ optical reflectance study of the development of the interface roughness of AlGaAs/AlAs distributed Bragg reflectors during the metalorganic vapour phase epitaxy growth of visible vertical-cavity surface-emitting laser structures. We show that the surface roughness can be extracted from time-resolved UV reflectance measurements. The roughness of the surface during growth for both the AlGaAs and AlAs layers can be determined individually. The values estimated from the in-situ optical data correlate well with the roughness measured ex-situ using atomic force microscopy. The in-situ reflectance measurement is thus shown to be a convenient non-invasive and non-destructive technique for determining surface and interface roughness even for complex device structures.