Performance of InGaN/GaN MQW LEDs Using Ga-Doped ZnO TCLs Prepared by ALD

Heavily Ga-doped ZnO (n(+)-GZO) films prepared by atomic layer deposition were used as transparent conducting layers (TCLs) on InGaN/GaN multiple quantum well (MQW) light emitting diodes (LEDs). It was found that N-2-annealed n(+)-GZO-coated InGaN/GaN MQW LEDs exhibited reduced forward voltage and enhanced light extraction under certain conditions. A forward voltage of 3.1 V at 20 mA was achieved for a 400 degrees C N-2-annealed n(+)-GZO-coated InGaN/GaN MQW LED with a specific contact resistance of the n(+)-GZO on p-GaN contact being 4.1 x 10(-3)Omega cm(2). Compared to the same InGaN/GaN MQW LED structure with a commercial-grade indium tin oxide (ITO) TCL, the 400 degrees C N-2-annealed n(+)-GZO-coated InGaN/GaN MQW LED shows an increment of light output power by 15% at 20 mA. It is believed that the enhanced light extraction of the n(+)-GZO-coated InGaN/GaN MQW LED is a consequence of a higher refractive index of n(+)-GZO than that of ITO.