Spatial characterization of a 2 in GaN wafer by Raman spectroscopy and capacitance-voltage measurements

Abstract

Micro-Raman spectroscopy and capacitance-voltage (C-V) measurements have been used to investigate 2 in GaN epitaxial wafers grown by hydride vapour phase epitaxy on sapphire substrates. The position and line shape of the A 1 longitudinal optical (LO) phonon mode were used to determine the carrier concentration at different locations across the wafer. The line-shape fitting of the Raman A 1 (LO) coupled modes taken from horizontal lateral-different positions on the wafer yielded a rudimentary spatial map of the carrier concentration. These data compare well with a carrier density map of the wafer obtained by C-V measurements, confirming the non-uniform distribution of carrier concentration in the GaN epitaxial film and that Raman spectroscopy of the LO phonon-plasmon mode can be used as a reliable and production friendly wafer quality test for GaN wafer manufacturing processes.