Effects of etching depth for n-contact and current spreading layer in InGaN/GaN light emitting diodes

Abstract

InGaN/GaN multiple quantum well (MQW) light-emitting diode (LED) structures possessing current spreading layers of various carrier concentrations were grown by a metal organic chemical vapour deposition method, and LEDs were fabricated with various etching depths for the n-contact. The current–voltage and light output power characteristics of these LEDs were investigated. Device properties of LEDs possessing a current spreading layer showed a lower operation voltage and a higher light output power than those without, although the reverse breakdown voltage decreased when the carrier concentration in the current spreading layer was too high. The best LED characteristics are shown in a LED with a carrier concentration of 6 × 1018 cm−3 in the current spreading layer. Operating voltages of LEDs at 20 mA show the best value at an etching depth for the n-electrode of 800 nm from the top layer. The depth of etching for the n-contact in a LED also affects the light output power. On the basis of our results, it is suggested that the etching depth for the n-contact and the carrier concentration of the spreading layer in InGaN/GaN LED should be controlled properly to obtain the best performance from LEDs.