AlInAs/GaInAs/AlInAs MODFETs fabricated on InP and on GaAs with metamorphic buffer - a comparison

Employing molecular beam epitaxy, we have grown identical Al(0.48)In(0.52)As/Ga(0.47)In(0.53)As/Al(0.48)In(0.52)As MODFET structures lattice matched to InP substrates asl as on GaAs substrates using a metamorphic buffer. To fabricate FETs on both substrate types, a fully planar process was developed using ion implantion for device isolation, electron-beam lithography for gate definition, and selective reactive ion etching for gate recess etching. Presently, a yield of 90 % for microwave transistors with 0.2 and 0.3 micron gate length and 70 % for 0.1-micron devices is achieved. For both substrate types, InP as well as GaAs with metamorphic buffer, very similar transistor performance was observed. Typically measured values are 800 - 900 mS/mm for g(ind (m,max)), -0.65 V for the threshold voltage, and 90 GHz and 165 GHz for f(ind T) for devices with 0.3 micron and 0.1 micron gate length, respectively. Hence, identical electron transport properties can be assumed for both substrates.