This paper reports on a high-quality AlGaN/GaN double heterostructure (DH) which shows UV emission stimulated by optical pumping at room temperature with low threshold power in both edge and surface modes, and a high-efficiency blue light emitting diode (LED) and UV-LED based on p-n GaN homojunction and AlGaN/GaN DH. The process for the fabrication of LEDs and DH and their characteristics are presented.