Influence of AlxGa1−xAs buffer layers on the performance of modulation-doped field-effect transistors

Abstract

Normally‐off and pseudo‐normally‐on modulation‐doped Al_0.3Ga_0.7As/GaAs Schottky barrier field‐effect transistors were fabricated and characterized. The structures were grown by molecular beam epitaxy and exhibited electron mobilities as high as 8000, 100 000, and 200 000 cm²/Vs at 300, 78, and 10 K, respectively. Inclusion of an Al_0.3Ga_0.7As buffer layer between the substrate and the modulation‐doped layers improved the transconductance and saturation characteristics substantially. This improvement was observed to be strongly dependent on the substrate temperature during the buffer layer growth, with the best results being obtained at 700 °C.