Luminescence study of a deep level in N-free GaP light-emitting diodes

Abstract
A 1.9-eV weak luminescence band observed at 77 K in nitrogen-free GaP light-emitting diodes grown by liquid phase epitaxy of Temperature Difference Method under Controlled Vapor Pressure in the vicinity of the optimum phosphorus vapor pressure has been studied. The relevant deep level has been found to act as a dominant nonradiative center at room temperature. The electroluminescence efficiency of the green emission band (555 nm at room temperature) and minority carrier lifetime are affected by this deep level. The centers which cause the 1.90-eV luminescence band are found to distribute in a p-type bulk region and also p-n interface region. It is proposed that the deep level is related to phosphorus vacancies.