A Comparison Between 20:1 and 5:1 Doping Ratios for High Efficiency X-Band GaAs IMPATT Diodes

High efficiency X-band GaAs IMPATT diodes with doping ratios of 20:1 and 5:1 are compared using hybrid coaxial-waveguide circuits. Both doping ratios yield diodes which show a factor of two increase in output power and efficiency when compared with similar uniformly doped diodes. Arrays of diodes are used to obtain output powers up to 5W. The increase in output power is almost linearly related to the number of diodes forming the array. Measurements of the AMand FM noise of representative diodes show that no significant noise penalty is incurred by using either doping ratio. The more difficult fabrication technology associated with the 20:1 doping ratio is not commensurate with the increase in RF performance, and a lower doping ratio can be used to equal effect.