D-BAND (110-170 GHZ) INP GUNN DEVICES

This paper reports on the development of InP Gunn sources for operation in the D-band (110-170 GHz). n+-n-n+ structures with flat doping as well as graded doping profiles have been considered. Oscillations were obtained at 108.3 GHz from a 1 mum structure with a uniform n doping of 2.5 x 10(16)cm-3. The CW RF output power was 33 mW. A 1 mum graded structure with an n doping increasing linearly from 7.5 x 10(15) to 2.0 x 10(16) cm-3 has resulted in 20 mW at 120 GHz and 10 mW at 136 GHz. These results are believed to correspond to a fundamental mode operation and represent the state-of-the-art performance from InP Gunn devices at these frequencies. This improvement in performance is attributed in part to a processing technique based on the use of etch-stop layers and InGaAs cap layers. An etch-stop layer allows low-profile mesas (2-3 mum) and InGaAs cap layers help reduce the contact resistance, thus minimizing series resistances in the device. In addition, a physical model based on the Monte Carlo method was developed to aid in the design of structures for high frequency operation. Experimental results obtained from a 1.7 mum Gunn device operating at W-band frequencies were used to estimate appropriate InP material parameters.