UV, blue, green, yellow-green and white LEDs fabricated by III-N semiconductors

Recent achievements in GaN-based light-emitting diodes (LEDs), which is linked to the use of new designs, such as p⁺-AlGaN/GaN strained-layer superlattice (SLS) and n⁺-InGaN/GaN short-period superlattice (SPS) top contact layer is reported. GaN-based LEDs with low-operation voltages, which are as low as 3 V (at 20 mA ) even lower, can be achieved by the use of these heavy-doped layers. In addition, conventional transparent conductive oxide, such as indium tin oxide (ITO), can be served as a transparent top contact layer in GaN-based LEDs other than thin metal film such as Ni/Au. Luminescence intensity in visible GaN-based LEDs can be significantly improved by this new design due to the high-transparency top contact layer. In the recent achievements, white LEDs including a variety of designs, such as phosphor-containing and phosphor-less device structures, will also be reported. Specifically, the high-efficiency yellow-green (λ∼565 nm) LEDs based on InGaN/GaN MQW emitting layers, which the luminescence intensity is comparable with the conventional AlGaInP yellow-green (λ∼575 nm) LEDs is achieved. This high-efficiency InGaN/GaN yellow-green LED makes a single-chip complementary white LED possible.