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-10nm 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 x 10(13)cm(-2), resulting in extremely low sheet resistances of 191 Omega/square. at RT and below 50 Omega/square at 77 K. These 2DEG properties exceed the best ones ever reported for III-N structures. The excellent current and power gain cutoff frequencies of 60 and 190GHz at V-DS = 15V obtained using 0.25 mu m technology reflect the outstanding 2DEG properties. (C) 2015 The Japan Society of Applied Physics