High-efficiency InGaN MQW blue and green LEDs

High-efficiency blue and green light-emitting diodes (LEDs) with multiple quantum well (MQW) InGaN active regions have been grown by low-pressure MOCVD on sapphire substrates. The devices have active regions composed of 12 InGaN wells clad by GaN barrier layers. A high density of crystallographically-oriented pits form during growth of the MQW layers and planarize during the growth of subsequent layers. Blue (similar to 470 nm) LEDs exhibit external quantum efficiencies of 10.6% at 20 mA and 8.7% at 100 mA. Green LEDs (522 nm) have external quantum efficiencies of 4.5% at 20 mA. Operating voltages as low as 2.96 V at 20 mA have been achieved. These are the highest efficiencies published to date for nitride-based MQW LEDs, Blue and blue-green device efficiencies are comparable to the best reported SQW devices at 20 mA drive current and exceed the SQW LEDs at higher currents. (C) 1998 Elsevier Science B.V. All rights reserved.