The spontaneous emission spectrum in n-type GaAs excited by a 40 kV electron beam at 300 K is theoretically determined for different values of the doping concentration. The procedure of determination is justified through reasonable agreement of the doping dependence of the peak emission energy and the linewidth of spontaneous emission as obtained from the computed cathodoluminescence spectra with that observed experimentally. Moreover, it is shown that the doping dependence of the low energy tail slope of the computed cathodoluminescence spectrum and the appearance of humps on the high energy side of this spectrum beyond a certain level of doping are also in agreement with the experimental observation. An attempt is also made to explain the origin of such humps.