CW Oscillations in GaAs planar-type bulk diodes

In order to realize practical GaAs bulk effect functional devices, it is necessary as a first step to demonstrate actually the capability of CW Gunn oscillation in planar-type diodes. This paper describes the results of CW oscillations obtained in GaAs planar-type bulk diodes. The n-type layer grown by vapor process on a Cr-doped semi-insulating substrate has 0.4-2 × 10¹⁵cm^-3carriers and is 10-35µ thick. Effective electrode spacing ranges 50-200µ. The most important things in obtaining reliable CW oscillations are the quality and geometry of the electrode-contacts as well as GaAs crystals of sufficient homogeneity. CW oscillations with satisfactory reliability have been obtained by adopting "I" and "T" shaped geometry for the n-type layer. The low-field resistance of the device is of the order of about 1kΩ. Fundamental oscillation frequencies of 0.5-3 GHz have been observed. The device construction and fabrication techniques as well as microwave oscillation characteristics such as output power, efficiency, etc., will be presented in detail.