Abstract:
We present an experimental and theoretical analysis of the nonlinear response of cooled extrinsic Ge photoconductors of the type used to detect far-infrared radiation. State of the art p-type Ge devices with nearly ideal noise performance in the absence of drive show characteristic subharmonic and chaotic nonlinear phenomena when periodically driven, with a corresponding degredation in noise performance by a factor ≈ 104. A systematic series of experiments and corresponding simulations of a standard model of extrinsic photoconductors, including measurings and simulations of the I-V curves, transient and small signal response, as well as the response to periodic drive, identify the physical transport processes responsible: the nonlinear electric field dependence of the rates of free hole capture and impact ionization due to carrier heating at relatively modest applied electric fields E > 0.1 V/cm. © 1986.
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