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 (HEMT) in the last years resulted in the best RF performance in the material system InAlAs/lnGaAs/InP. Nevertheless, some problems like the kink-effect or photoconductivity arise that are related to aluminium containing layers. These problems can be avoided by using InP instead of InAlAs. InP/InGaAs/InP HEMTs grown by LP-MOCVD using H/sub 2/ as carrier gas demonstrated very good RF performance. We present now the first data of Al-free HEMTs grown by LP-MOCVD using a nitrogen carrier, which improves the growth process in terms of homogeneity, safety and costs. We show that Zn diffusion affects the performance of those HEMTs and can be suppressed by inserting an InGaP layer below the p-doped InP that acts as diffusion barrier for Zn. This diffusion barrier allows smaller gate to channel separations resulting in improved RF performance of f/sub T/=135 GHz and f/sub max/=200 GHz for 0.2 /spl mu/m T-gate HEMTs.