ZnO-on-GaN heterojunction light-emitting diode grown by vapor cooling condensation technique

The growth of ZnO-on-GaN heterostructures was implemented using the vapor cooling condensation system. The technique thus developed was employed to fabricate both the p-GaN/n-ZnO:In (p-n) and p-GaN/i-ZnO/n-ZnO:In (p-i-n) heterojunction light-emitting diodes (LEDs). A rectifying diodelike behavior was clearly observed from both the p-n and p-i-n heterojunction LEDs, with the forward turn-on voltage of 3 V and the reverse breakdown voltage of -15 V determined for the p-n heterojunction LEDs, compared to 7 and -23 V, respectively, for the p-i-n heterojunction LEDs. Based on the results of photoluminescence and electroluminescence studies conducted on these LED structures, the ZnO layer responsible for the peak emission wavelength of 385 nm were also verified experimentally.