Photoluminescence studies of nitrogen doped gallium phosphide grown by liquid phase epitaxy

Abstract

GaP:N grown by Liquid Phase Epitaxy (LPE), exhibits several photoluminescence peaks at low temperatures (< 10K). In this study we observe that the PL intensity increases with temperature and exciting laser power upto a critical value beyond which it decreases. A model is presented to explain such dependences. The temperature behaviour is attributed to the initial increase in the number of radiative recombinations owing to thermal relaxation of carriers followed by the ionization of holes in the bound exciton, thereby leading to a sharp fall in the LP intensity. On the other hand, the initial increase in PL intensity with laser power, as per our model, is due to the larger number of carriers getting excited into the conduction band; the subsequent decrease in intensity being due to the increase in phonon-assisted non-radiative recombinations owing to many-body interactions of the larger number of carriers.