Low noise epitaxial GaAs avalanche diode amplifiers

This paper describes the experimental results obtained with an x-band reflection amplifier using vopor phase epitaxial, GaAs p-n junctions biased into avalanche breakdown. The noise figures obtained with a large number of these diodes are significantly lower than those reported for Si or Ge diodes. Noise figures as low as 17 db and power gains in excess of 30 db have been repeatedly measured with diodes operated at current densities of the order of 200 amperes/cm². The corresponding published noise figures for Si and Ge avalanche diode amplifiers range from 30 to 40 db. Detailed measurements on an amplifier tunable from 8.2 to 9.4 GHz for various bias and coupling conditions are discussed. The results presented include complete gain, noise, and dynamic range characteristics. The properties of the vapor hydride epitaxial material and the construction details of the chemically formed mesa diodes are also presented.