Electron-hole avalanches in semiconductors

An analytical theory of the development of electron - hole avalanches in semiconductors, which qualitatively differ from the electron avalanches in gases, is proposed and the spatiotemporal distributions of the field and charge in such avalanches are determined. It is suggested to identify the onset of the avalanche - streamer transition as the moment (t(a)) corresponding to a 20% decrease in the impact ionization coefficient alpha at the avalanche center. A transcendent equation is obtained for the calculation of t(a) as a function of the unperturbed coefficient alpha( E-ext) determined by the external field E-ext. It is established that, as the alpha( E-ext) value is increased in from 10(3) to 10(5) cm(-1), the total number of electron - hole pairs generated by the t(a) moment decreases by almost three orders of magnitude.