Properties of Zn-doped VPE-grown GaN. II. Optical cross sections

Abstract

Experimental data are presented for optical cross sections σ0n(hν) related to the four deep acceptorlike Zn-related radiative levels A–D in GaN. Very accurate spectral data were obtained by the photoluminescence excitation (PLE) technique, at temperatures varying from 4.2 up to 293 K. From a detailed comparison of the spectral behavior of the emission and absorption spectra, the size of electronic broadening effects could be determined in the overlap region. The binding energies for Zn-related acceptor levels were obtained as EA=0.34±0.04, EB=0.65±0.08, EC=1.02±0.05, and ED=1.42±0.08 eV at low temperature. Optical transmission data give estimates of absolute values for optical cross sections at saturation, varying from σ0nA(sat) ?1×10−16 to σnD(sat) ?5×10−18 cm2. Temperature broadening effects in optical cross sections are well explained by a linear model for phonon coupling in the optical transitions, employing the same phonon energies and coupling strengths as were evaluated from emission spectra.