High quantum efficiency of violet-blue to green light emission in InGaN quantum well structures grown by graded-indium-content profiling method

Optical characteristics of high-efficiency violet-blue, blue, and green light emissions in In x Ga 1 − x N quantum well (QW) structures with graded In content are investigated. Appearance of additional higher energy peaks at 410, 429, and 459 nm above the main peaks at 430, 463, and 509 nm with an effective carrier transfer from the higher to main peak sides is characteristic of these structures with various In contents of x < 0.2 , 0.2 < x < 0.3 , and x > 0.3 , respectively. Robust carrier localization by uniform, small-size, and high-density phase segregation plays an important role in maintaining high efficiencies over a wide range of In contents in graded-In-content InGaN QW structures.