GaAs W-band IMPATT diodes - The first step to higher frequencies

The principles of design and impedance modeling of IMPATT diodes are described, and the device technology and experimental results are reviewed with emphasis on noise performance. Attention is focused on breakdown voltage values, the ionization rates, drift velocities, and the avalanche zone. A selective etching technology used for reducing series resistance due to the skin effect and thick substrate layer is discussed. It is observed that GaAs may become a candidate material for realizing IMPATT diodes for frequencies above 90 GHz if accurate material parameters such as ionization rates and drift velocities are taken into consideration. The noise performance with a noise level of 20 dB at 10 mW and 94 GHZ with a noise-to-carrier ratio of - 82 dBc at a modulation frequency of 100 kHz is found to be comparable to Gunn devices, offering better power capabilities.