InGaN/AlGaN blue-light-emitting diodes

Highly efficient InGaN/AlGaN double-heterostructure blue-light-emitting diodes (LEDs) with an external quantum efficiency of 5.4% were fabricated by codoping Zn and Si into an InGaN active layer. The output power was as high as 3 mW at a forward current of 20 mA. The peak wavelength and the full width at half maximum of the electroluminescence of blue LEDs were 450 and 70 nm, respectively. Blue-green LEDs with a brightness of 2 cd and a peak wavelength of 500 nm were fabricated for application to traffic lights by increasing the indium mole fraction of the InGaN active layer.