LOW-TEMPERATURE PHOTOLUMINESCENCE OF N-INSE LAYER SEMICONDUCTOR CRYSTALS

Low-temperature photoluminescence spectra of n-InSe layered single cry stals were studied in the temperature range 10-210 K. Photoluminescenc e of n-InSe showed peaks at 1.334, 1.306, 1.288, and 1.232 eV at 10 K. These four peaks were attributed to radiative recombination of the di rect free excitons, an impurity-band transition, a donor-acceptor reco mbination channel, and the transition within an impurity-vacancy compl ex, respectively. To determine the temperature dependence of direct ba nd gap of n-InSe, we estimated the exciton binding energy to be 15 meV by assuming an isotropic approximation for the anisotropy parameter g amma = 1. From these peak positions and the estimated band gap, the do nor and acceptor levels associated with these centers were estimated t o be approximately 43 and 18 meV, respectively. The temperature variat ions of the peak energy and linewidth of the excitons in n-InSe were e xplained by taking into account both the exciton-acoustic-phonon and t he exciton-optical-phonon interactions. Below approximate to 60 K, the se variations are due mainly to exciton scattering by acoustic phonons via the deformation potential in InSe. (C) 1998 Elsevier Science Ltd.