High electron mobility in high-polarization sub-10 nm barrier thickness InAlGaN/GaN heterostructure

We report on the improvement of the electron transport properties of the two-dimensional electron gas (2DEG) confined at a nearly lattice-matched quaternary barrier InAlGaN/AlN/GaN heterostructure using a sub-10 nm ultrathin barrier. Electron mobilities of 1800 (RT) and 6800 cm 2 V −1 s −1 (77 K) are achieved while delivering a high electron density of 1.9 × 10 13 cm −2 , resulting in extremely low sheet resistances of 191 Ω/□ at RT and below 50 Ω/□ at 77 K. These 2DEG properties exceed the best ones ever reported for III–N structures. The excellent current and power gain cut-off frequencies of 60 and 190 GHz at V DS = 15 V obtained using 0.25 µm technology reflect the outstanding 2DEG properties.