InP HEMTs employing strain-compensated Al-rich InAlAs for low-noise and low-power consumption

Abstract

InP high electron mobility transistors (InP HEMTs) have attracted attention as cryogenic low noise amplifiers (LNAs) for quantum computing due to their high speed, high gain, and low-noise characteristics. Reducing gate leakage current is critical for achieving low-noise performance in InP HEMTs. Conventional approaches have mainly focused on optimizing the thickness of the lattice-matched In0.522Al0.478As layer to suppress the leakage current. However, leakage current still remains a major issue. Here, we propose a bandgap engineering approach using Al-rich In0.362Al0.638As layers to decrease the gate leakage current without increasing the layer thickness in InP HEMTs. The increased bandgap in Al-rich InAlAs decreases the gate leakage current and enhances electron confinement effect at the same thickness. In addition, the Al-rich InAlAs layer enables strain compensation for In-rich InGaAs channel layer and decrease the gate capacitance, which is favorable for high-speed operation. We successfully demonstrated low gate leakage InP HEMTs incorporating Al-rich In0.362Al0.638As in both the buffer and the spacer layers. Our InP HEMTs exhibited superior performance, achieving a high Ion/Ioff ratio of 1.5 × 105, a steep subthreshold swing (SS) of 65 mV/dec, and a high effective mobility of more than 9000 cm2/Vs, while maintaining a low gate leakage current of less than 6 nA/μm. This study will provide design guidelines for future low-noise InP HEMTs research.