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

Abstract
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.