STUDIES OF GAASER IMPACT EXCITED ELECTROLUMINESCENCE DEVICES

We report on the study of impact excitation of Er ions in GaAs. The me talorganic chemical vapor deposition grown, p+-n structured electrolum inescence (EL) devices were fabricated by growing, at different temper atures, GaAs:Er layers on top of the n+ GaAs substrates. P+ layers of GaAs were made by Zn diffusion from the top surfaces. When we forward biased these diodes, the EL spectra were similar to the respective pho toluminescence (PL) spectra of each sample. The spectra of the samples differed for the various growth temperatures. However, when we revers e biased these diodes, the EL spectra are the same for all samples but different from the PL spectra. These results indicate that the Er cen ter(s) excited by direct impact is different from the Er center(s) exc ited through electron-hold recombination and the subsequent energy tra nsfer.