Sidegating-Induced Negative Differential Resistance in MBE-Grown InAs/AlSb HFETs

Abstract

We report sidegating measurements on mesa-isolated InAs/AlSb-based heterojunction field effect transistors (HFETs) grown on GaAs semi-insulating substrates with thick strain-relaxed AlSb buffer layers. We find that the AlGaSb/AlSb buffer layers provide adequate inter-device isolation for low sidegate voltages |V SG|<5 V. For sidegate electrode voltages of ±20 V, the substrate leakage current remains lower than 100 nA for a sidegate separation of only 4 µ m from the active channel. For large positive sidegate voltages, a marked sidegating-induced negative differential resistance (SINDR) appears in the drain characteristics. The peculiar frequency and temperature dependencies of the SINDR effect indicate that the negative differential resistance is caused by a transient occupation of deep level centers by holes injected into the buffer layers from the sidegate electrode. In contrast, large negative sidegate voltages have a negligible impact on the HFET drain characteristics. The present results illustrate the importance of buffer layers in InAs/AlSb HFETs and call for a deep level transient spectroscopy characterization of deep centers in InAs/AlSb HFET buffer layers.