InGaN/GaN multiple quantum wells on selectively grown GaN microfacets and the applications for phosphor-free white light-emitting diodes

Phosphor-free InGaN/GaN multiple quantum well (MQW) white light-emitting diodes (LEDs) have the advantages of simpler device process and potentially higher efficiency, and have attracted much attention in recent years. A host of technologies are emerging for implementing such white-light LEDs. Among them, the key issue is the color tuning of different emission wavelengths from InGaN/GaN MQWs with different indium (In) content. However, owing to the limited growth technology for long-wavelength InGaN/GaN MQWs with high In content, it is very attractive to study selective area epitaxy (SAE) of InGaN/GaN MQWs on GaN microstructures with non- or semipolar microfacets combined with (0001) c-plane. In this paper, we briefly review the previous developments of InGaN/GaN MQW based phosphor-free white light LEDs, then the particular technology for the growth of InGaN/GaN MQWs on the regrown GaN microfacets using SAE has been introduced, and related mechanisms for the formation of different non- or semipolar GaN microfacets fabricated by various mask patterns are discussed in detail. Furthermore, sophisticated approaches made use of the InGaN/GaN MQWs on GaN microfacets to fabricated phosphor-free white light LEDs with polychromatic emissions are reviewed.