Spatial variations of doping and lifetime in epitaxial laterally overgrown GaN

Spatial variations of donor concentration and diffusion length/lifetime were studied for epitaxial laterally overgrown undoped n-GaN samples by electron beam induced current (EBIC) and microcathodoluminescence (MCL). The dependence of the EBIC signal collection efficiency on the probing beam accelerating voltage shows that the local electron concentration is three times lower and the local lifetime about twice as high in the laterally overgrown regions compared to the regions grown in the SiO₂ mask windows. Band edge MCL profiling shows that the lifetime difference could be an order of magnitude higher. EBIC scans along the SiO₂ stripes in the low dislocation density overgrown regions show long propagation distances of holes in the quasineutral part of the structure, explained by the existence of a potential profile forming a trough for transport of holes while spatially separating nonequilibrium carriers.