0.2 /spl mu/m T-gate InP/InGaAs/InP pHEMT with an InGaP diffusion barrier layer grown by LP-MOCVD using an N/sub 2/-carrier

The development of the High Electron Mobility Transistor for millimetre-wave applications has resulted in best RF performance in the material system InAlAs/InGaAs/lnP. Nevertheless, some problems like photoconductivity and kink-effect arise, which are related to aluminium containing layers. These problems can be avoided by using InP instead of InAlAs. HEMTs with very good RF performance have been fabricated in the material system InP/InGaAs/InP. These structures were grown by LP-MOCVD using H/sub 2/ as a carrier gas. We present now the first data of InP/InGaAs/InP HEMTs grown by LP-MOCVD using an nitrogen carrier, which improves the growth process in terms of homogeneity, safety and costs. To avoid short channel effects at small gate lengths the gate to channel separation has to be kept as small as possible. This distance is limited by the thickness of the p-doping layer and by diffusion of Zn atoms into the supply layer and the channel. We show that the insertion of a InGaP layer between p-doping and separation layer reduces Zn diffusion and therefore enables the growth of smaller gate to channel separation. HEMTs with 0.2 /spl mu/m gate length yield cutoff frequencies of f/sub T/=110 GHz and f/sub max/=200 GHz.