This paper reports on the development of InP Gunn sources for operatio
n 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 operat
ion and represent the state-of-the-art performance from InP Gunn devic
es at these frequencies. This improvement in performance is attributed
in part to a processing technique based on the use of etch-stop layer
s and InGaAs cap layers. An etch-stop layer allows low-profile mesas (
2-3 mum) and InGaAs cap layers help reduce the contact resistance, thu
s minimizing series resistances in the device. In addition, a physical
model based on the Monte Carlo method was developed to aid in the des
ign of structures for high frequency operation. Experimental results o
btained from a 1.7 mum Gunn device operating at W-band frequencies wer
e used to estimate appropriate InP material parameters.