Degradation of bulk luminescence in GaP : Zn,O induced by laser excitation

Bulk degradation of GaP : Zn,O LED material has been studied using above-band-gap laser light as the means of excitation. Significant bulk degradation can be induced at elevated temperatures by ?103 W/cm2 of 5145-Å laser excitation. The degradation is quite uniform and extends 20 μm into the crystal, conforming to the volume excited by the laser. SEM and luminescence studies show that the minority-carrier diffusion length changes only slightly during degradation, whereas the Zn-O luminescence decreases by as much as an order of magnitude. It is concluded that the degradation is due to the reduction of the Zn-O complex concentration.