Electron beam and optical depth profiling of quasibulk GaN

Electron beam and optical depth profiling of thick (5.5-64 mu m) quasibulk n-type GaN samples, grown by hydride vapor-phase epitaxy, were carried out using electron beam induced current (EBIC), microphotoluminescence (PL), an d transmission electron microscopy (TEM). The minority carrier diffusion le ngth, L, was found to increase linearly from 0.25 mu m, at a distance of ab out 5 mu m from the GaN/sapphire interface, to 0.63 mu m at the GaN surface , for a 36-mu m-thick sample. The increase in L was accompanied by a corres ponding increase in PL band-to-band radiative transition intensity as a fun ction of distance from the GaN/sapphire interface. We attribute the latter changes in PL intensity and minority carrier diffusion length to a reduced carrier mobility and lifetime at the interface, due to scattering at thread ing dislocations. The results of EBIC and PL measurements are in good agree ment with the values for dislocation density obtained using TEM. (C) 2000 A merican Institute of Physics. [S0003-6951(00)00643-4].