ZnO-based homojunction light-emitting diodes fabricated by metal-organic chemical vapor deposition

ZnO p-n homojunction light-emitting diodes were fabricated on p-GaAs substrates by metal-organic chemical vapor deposition. The current-voltage characteristics showed a diode characteristic between the n-type and p-type ZnO layers with a threshold voltage of 3.8 V. We present a room-temperature study of photoluminescence (PL) spectra and electroluminescence (EL) spectra. The PL spectra of both n-type and p-type ZnO exhibited strong near-band-edge emission and weak broad deep-level emission peaks. The EL spectra showed a strong broad deep-level emission when the injection current attained 40 mA, and a weak ultraviolet emission emerged when the current attained 150 mA.