The direct-bandgap III-Nitride semiconductor family and its alloy span the widest spectral range among all the semiconductors, ranging from the infrared (InN at 0.65 eV) through the visible and ultra-violet (UV) (GaN at 3.42 eV) to the deep UV range (AlN at 6.2 eV). This unique property along with their superior physical and chemical characteristics provides the wide applications in the solid-state lighting, laser diodes, high-frequency and high-power electronic devices, photovoltaic cells, etc. In the III-Nitride family, In-rich In_xGa_1-xN devices are less developed due to the challenge to realize p-type doping even if it has promising applications in the long-wavelength emitting and ultra-high-efficiency solar cells. We will solve this worldwide puzzle of p-type doping in In-rich In_xGa_1-xN by intelligently designing the growth technique.

Three primary color-mixing based on one material system is the most effective way to realize white light emitting. Up to now, only blue and green LEDs can be achieved using low In content In_xGa_1-xN. It is impossible to generate red emitting by using In_xGa_1-xN. On the other hand, although a high power conversion efficiency of more than 50% was expected for In_xGa_1-xN multi-junction photovoltaic cells, the practical values are much smaller (<3%). In order to make breakthrough in semiconductor lighting and to achieve the highest-efficiency solar cells, the novel physical strategies and device concepts are extremely urgent to overcome these drawbacks in III-Nitride material system.