ABSTRACT
It is now established that the performance of blue/green GaN based light emitting diodes (LEDs) (Nakamura and Fasol, 1997a) is superior to conventional red AlGaAs or AlinGaP LEDs with respect to output power and reliability in spite of large threading dislocation (fD) density up to the order of 1010 cm·2 (Rosner et al., 1997). The dislocation density in ZnSe based II-VI laser material is as low as less than 104 cm·2. However, both the output power and device lifetime of GaN based purplish-blue LDs (Nakamura and Fasol, 1997a) are better than those of II-VI materials. Therefore the open question has been why InGaN LEDs exhibit highly efficient bright emissions despite of the large TD density.
