Semiconductor models for first and second order non-equilibrium phase transitions

Non-equilibrium phase transitions in semiconductors due to impact ionization from traps have been obtained theoretically, and are discussed in detail. They include first and second order phase transitions, and develop previous work, which was restricted to second order phase transitions involving band-band processes. The models include switching transitions from non-conducting to conducting states, and from n- to p-type states. They furnish simple illustrations of the general principle that a system which is driven far from equilibrium can exhibit new stable steady states.