Impurity effects on low temperature photoluminescence of GaSe

The low temperature luminescence of GaSe has been measured on a series of single crystals, some of which were doped with tin, copper, zinc, iodine, or cadmium. Concentrations and activation energies of the impurities have been determined by electrical measurements. At 4.2 °K, radiative recombination of electron–hole pairs occurs via two channels, whose relative efficiency is governed by the total impurity concentration. The first channel is most efficient in pure crystals. It gives rise to a spectrum dominated by the free exciton lines. The second channel is most efficient in doped crystals. Its spectrum is not sensitive to the chemical nature of the impurities. It is attributed to structural defects which are created by the chemical impurities.