Mechanical stress induced defect creation in GaP

Abstract

The concentration of a donor like deep level - T₇ - about 0.8 eV from the conduction band has been correlated to the amount of accumulated mechanical stress in GaP p-n structures. Under forward bias stressing the initial concentration of T₇ decreases. Depending on the local strain field pattern new levels appear. If compressive strain field is dominant within the p-n junction, the level created is 0.49 eV below the conduction band. If the strain field is absent two levels - 0.71 eV and 1.18 eV below the conduction band - are created. We tentatively identified the latter two levels as the two charge states Of P_Ga - phosphorus antisite defect. Both defects act as non-radiative recombination centres, hence responsible for the performance degredation of GaP LED's.