First demonstration of AlInAs/GaInAs HEMTs on AlAsSb and oxidized AlAsSb buffers

We report for the first time two new AlInAs/GaInAs HEMT device structures, one fabricated on a thin AlAsSb buffer and the other on an oxidized AlAsSb buffer. AlAs_0.56Sb_0.44 which is lattice matched to InP has a bandgap of 1.9 eV compared to 1.45 eV for AlInAs. This increases the barrier between the channel and the substrate, reducing parasitic conduction through the buffer, and improves the charge control properties. Also AlAsSb can be converted to Al₂O₃ by lateral oxidation in steam to obtain a truly insulating buffer. An AlInAs/GaInAs HEMT with an AlAsSb buffer with Lg=1.5 μm has Ids=500 mA/mm and gm=810 mS/mm. AlInAs/GaInAs HEMTs with an oxidized AlAsSb buffer have gm=190 mS/mm for Ids=130 mA/mm