Emission of Cuprous Halide Crystals at High Density Excitation

Super-linear luminescences of cuprous halide crystals under the high density excitation by an N 2 -laser have been studied at temperatures above 100 K, where excitons and free charge carriers are considered to co-exist. A new emission, which is called H band, is found in CuCl, CuBr and CuI crystals. The H band has an asymmetric shape tailing to the low energy side. The peak energy, measured from the exciton band, varies linearly with temperature. By assuming that the emission is due to the interaction of exciton with free electron, the properties of the H band are explained and the effective masses of the electron and hole are obtained as m e =0.43 m o , m h =4.2 m o in CuCl, m e =0.28 m o , m h =1.4 m o in CuBr and m e =0.33 m o , m h =14 m o in CuI crystals.