Enhancement in electrical and optical properties of field-effect passivated GaN blue light emitting diodes

This paper investigates the field-effect sidewall surface passivation of III-Nitride blue light emitting diodes (LEDs) using ultrathin films of Al2O3 and ZnO grown using atomic layer deposition. A large density of negative fixed charges existing at the sidewall surface of the passivation layer leads to formation of an electric field at the interface of the passivation layer and the GaN layer. This repels the free negative charge carriers from getting close to the surface of the semiconductor and being trapped there. It also reduces the non-radiative recombination of these charge carriers and eventually leads to enhancement in electrical and optical properties of these devices. Electrical measurements demonstrate a significant decrease in the leakage current and the ideality factor in addition to a notable increase in the parasitic shunt resistance of the field-effect-passivated GaN LEDs compared to non-passivated devices. The field-effect passivation can be especially useful for smaller LED die size. In such a device, the effect of high leakage current at the edges of the device is more detrimental to its performance. The proposed approach can further eliminate the shunt conduction paths along the sidewalls of the LED and increase the efficiency of the devices.