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

Kuo-Yi Yen Kuo-Yi Yen,Tai-Yuan Lin Tai-Yuan Lin,Pei-Shin Lin Pei-Shin Lin,Tzu-Pei Chen Tzu-Pei Chen,Chien-Hua Chiu Chien-Hua Chiu,Chien-Hua Chou Chien-Hua Chou,Jyh-Rong Gong Jyh-Rong Gong,Chun-Wei Li Chun-Wei Li

doi:10.1109/lpt.2012.2220537

Abstract

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°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 × 10 -3 Ω cm 2 . Compared to the same InGaN/GaN MQW LED structure with a commercial grade indium tin oxide (ITO) TCL, the 400 °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.

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