111-V nitride-based short-wavelength LEDs and LDs*

Abstract

Abstract Much research has been done on high-brightness blue light-emitting diodes (LEDs) and laser diodes (LDs) for use in full-color displays, full-color indicators, and light sources for lamps with the characteristics of high efficiency, high reliability, and high speed. For these purposes, II-VI materials such as ZnSe [1, 2], SiC [3], and III-V nitride semiconductors such as GaN [4] have been investigated intensively for a long time. However, it was impossible to obtain high-brightness blue LEDs with a brightness over 1 cd and reliable LDs. Much progress has been achieved recently on green LEDs and LDs using II-VI-based materials [5]. The short lifetimes prevent II-VI-based devices from commercialization at present. It is considered that the short lifetime of these II--VI based devices is caused by crystal defects at a density of 103/cm2, because one crystal defect would cause the propagation of other defects leading to failure of the devices. SiC is another wide bandgap material for blue LEDs. The brightness of SiC blue LEDs is only between 10 med and 20 med because of the indirect bandgap of this material. Despite this poor performance, 6H--SiC blue LEDs have been commercialized for a long time because there has been no competi¬ tion for blue light-emitting devices [6].