ELECTRON GLASS-TRANSITION IN A LIGHTLY DOPED SEMICONDUCTOR

A temperature-induced transition in the distribution of electrons over impurities in a lightly doped semiconductor is studied by a Monte Carlo computer simulation. Such a transition from a correlated distribution at low temperatures (electron glass) to a random distribution at high temperatures was studied recently by photo-thermal magnetospectroscopy experiments and appeared to be very sharp. We show here that this transition under thermal equilibrium conditions is relatively smooth. However, if the thermal equilibrium conditions fail at some temperature, the system possesses a sharp transition very close to that observed in the experiment. Therefore the sharpness of the transition comes not from the nature of the electron glass but from the freezing of the process, which leads to the thermalization of the system. In a lightly doped semiconductor this process is the activation of electrons from donors to the conduction band. The shape of the transition depends on the time scale of the experiment as in structural glasses. Desirable experiments are suggested which can verify the theoretical picture.