Electrical and optical characterization of GaN HVPE layers related to extended defects

Abstract

The study of the effect of extended defects, present in very large numbers in GaN epilayers, on the material properties and device performance is one of the most important aims of the current research in the field of III nitrides. Thickness strongly influences electrical and optical properties of epitaxially grown GaN. Due to the lattice mismatch between sapphire and GaN, extended defects (mainly threading dislocations) are generated at the sapphire/epilayer interface, and a degenerate layer, characterized by high defect density and high conductivity. has been observed. Movin toward the top surface, the density of the extended defects, which seem to greatly affect the material properties. gradually decreases. This fact mainly causes the commonly observed electrical and optical inhomogeneities. This work deals with the comparative study by means of optical and electrical characterization between two HVPE-grown layers with different thickness (2.6 and 55 mum) in order to check the effects of the extended defect distribution across the sample.