Quantum-mechanical estimates of the speed of field ionization of shallow impurity levels

Using a Kohn-Luttinger approach to shallow impurity levels in semiconductors, we estimate the speed of charge release associated with field ionization. At sufficiently low temperatures, this is predominantly a quantum-mechanical process. It is found that charge release times in the picosecond regime may be achievable in prebreakdown fields in semiconductors. In GaAs, one picosecond release times correspond to fields of 0.2 V/μ and field energy densities of 2×10−18 J/μ3. In the picosecond regime, our estimates rely on published, mutually consistent Stark width results obtained by various techniques including dispersion relations and Weyl’s complex-eigenvalue method.