A MODEL FOR THE CURRENT INSTABILITIES IN GAAS-ALGAAS HETEROJUNCTION

A model is proposed for the description of the current instabilities i n GaAs-AlGaAs heterojunctions. It consists of three parts: the injecti on of electrons via the contact into the AlGaAs layer, the partial cap ture of these electrons in deep centers, and the change with time of t he band structure. This last ingredient is crucial, since due to the i ncrease of the total number of electrons in the AlGaAs layer the band bending decreases making real-space transfer from the AlGaAs layer to the two-dimensional electron gas possible. We have performed quasistat ionary simulations of the time dependence of the current. The velociti es, average energies, capture rates, etc. were taken from Monte Carlo simulations. It turned out, that the parameters for the modeling of th e contact, which are to a high degree unknown, play an essential role. (C) 1996 American Institute of Physics.