Abstract
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 (∼470nm) LEDs exhibit external quantum efficiencies of 10.6% at 20mA and 8.7% at 100mA. Green LEDs (522nm) have external quantum efficiencies of 4.5% at 20mA. Operating voltages as low as 2.96V at 20mA 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 20mA drive current and exceed the SQW LEDs at higher currents.
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