InGaN based light emitting diodes utilizing Ga doped ZnO as a highly transparent contact to p‐GaN

We report on the electrical and optical properties of InGaN based light emitting diodes (LEDs) utilizing Ga doped ZnO (GZO) grown by MBE as a highly transparent contact p ‐electrode (GZO‐LEDs). For comparison, the LEDs with semi‐transparent thin Ni/Au (5nm/5nm) current spreading layers were also fabricated on the same wafer (Ni/Au‐LEDs). Pulsed electroluminescence measurements revealed that the relative external quantum efficiency (EQE) of the GZO‐LED is 1.7‐2 times higher than that of Ni/Au‐LED at high current densities. Moreover, GZO‐LEDs can withstand much higher current densities (4700 A/cm2) than the Ni/Au LEDs (3500 A/cm2) under pulsed mode. Unpackaged GZO‐LEDs with 200 μm diameter showed negligible light output degradation for up to 30 mins under CW current of 100 mA (corresponding to a 318 Acm‐2 current density), while the light output for Ni/Au‐LEDs was reduced by 85% after only 5 mins of operation due to the severe current crowding effect (or current filamentation). (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)