Zinc oxide-based current spreading layer behavior on the performance of P-side-up thin-film red light emitting diodes

Transparent conductive layers deposited on a GaP window layer were used to fabricate high-brightness p-side-up thin-film AlGaInP light emitting diodes (LEDs). Zinc oxide (ZnO) and aluminum-doped zinc oxide (ZAO) with an Zn:Al cycle ratio of 20:1 were grown by atomic layer deposition for comparison. The ZAO thin films reduced the droop in the external quantum efficiencies of the LEDs as well as the junction temperature, which result in increases in the light output power and thermal stability of the LEDs. The efficiency droops of the LEDs with the ZnO and ZAO thin films were 41% and 15%, respectively. The junction temperature of the LED with the ZAO thin film can be reduced to 39.6 °C at an injection current of 700 mA, which is lower than that of the LED with the ZnO thin film (58.1 °C). The above results are promising for the development of ZAO thin films for applications in AlGaInP LEDs.