A Low Noise Impatt Diode

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A sequence of AlxGa1-xAs, GaAs hetrojunctions can be used to generate a series of potential steps which are just large enough to accelerate conduction band electrons above the threshold for impact ionization leading to current multiplication of the form I=Io2n+. The smaller valance band discontinuity and higher scattering rates can be used to suppress the initiation of impact ionization by valence band electrons. The resulting structure is predicted to be a low noise amplifier and to be insensitive to small fluxuations in the power supply voltage. By picking appropriate layer widths the transit time can be made to give a negative impedance at the desired frequency which can be used as either an amplifier or an oscillator. It is proposed that tests be carried out on the two wafers already fabricated by the National Submicron Laboratory at Cornell and that additional wafers will be grown with appropriate variations in parameters to improve the performance and enhance our understanding of the stepped structure.