Properties of Zn-doped VPE-grown GaN. I. Luminescence data in relation to doping conditions

Abstract

Experimental results on optical and electrical properties of VPE-grown GaN doped with Zn under various conditions of growth are presented. The incorporation of Zn into GaN was found to be critically dependent on growth conditions. Four different Zn-related acceptorlike centers A–D were found to occur, with broad radiative emissions peaking at 2.87 (A), 2.6 (B), 2.2 (C), and 1.8 eV (D). Their broad shape was found to be due to a moderate lattice relaxation upon optical transitions. A linear model for phonon coupling was found adequate, with a principal mode resonant with the optical band [h/ω, varying between 74 (A level) and about 84 meV (C level)] and an additional lower-energy mode, yielding Franck-Condon shifts for these centers ΔFC,A =0.25±0.03, ΔFC,B=0.25±0.04, ΔFC,C =0.28±0.04 eV, and ΔFC,D=0.28±0.05 eV. Data for electrical compensation related to the occurrence of these different emissions indicate that the A level could be the ZnGa substitutional acceptor, while the more efficiently compensating B–D levels might be associated with Zn occupying N sites.