Fabrication and characterization of GaN FETs

The current status of GaN-based FET technology and performance is reviewed. The fabrication details and the de and microwave characteristics of GaN MESFETs that utilize Si-doped channels on semi-insulating buffer layers are presented. MESFETs with a 0.8 mu m gate have exhibited an f(T) and f(max) of 6 and 14 GHz, respectively. These devices have excellent pinchoff characteristics and a source-drain breakdown voltage of over 85 V. A high-field current-collapse phenomenon is observed in these MESFETs in the absence of light. The characteristics of this current collapse as a function of temperature, illuminating wavelength, and time are described. A model describing the current collapse in terms of hot electron injection into the buffer layer is presented. Elsevier Science Ltd.