Carrier density imaging of lateral epitaxially overgrown GaN using scanning confocal Raman microscopy

GaN thin films, grown by the lateral epitaxial overgrowth (LEO) method, are studied by scanning confocal Raman microscopy. By measuring changes in coupled longitudinal-optical phonon-plasmon frequencies and using a standard harmonic oscillator dielectric function, detailed images of carrier density could be formed. Carrier concentrations are extremely high (similar to 10(20) cm(-3)) immediately above SiO(x) mask layers and decrease abruptly when the SiO(x) mask are not directly exposed to the growth surface, implying that SiO(x) masks are the source of dopants. Images of intergrated E(1) longitudinal-optical phonon intensities could be compared with free-carrier images and showed a clear anticorrelation throughout the LEO structure. (C) 2001 American Institute of Physics.