Abstract
A general expression for the small‐signal microwave conductivity of a nonequilibrium electron plasma is derived in terms of the momentum distribution function. The dependence of conductivity upon the orientation of the microwave field with respect to a steady bias electric field is presented in detail. Carrier‐phonon relaxation processes, such as those characteristic of polar semiconductors, lead to large variations of conductivity with frequency. For certain electron scattering models approximate to GaAs, the present results illustrate how a population inversion discovered by Fawcett and Rees could lead to wide band maser action at submillimeter‐wave frequencies.

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