InAlN/GaN HEMT on Si With fmax =270 GHz

Device surface properties are critical for its performance such as channel electron density, leakage current, subthreshold swing (SS), and noise in gallium nitride high-electron-mobility transistors (HEMTs). In this article, the improved surface property of InAlN/GaN HEMTs with forming gas (FG, 5% H-2, and 95% N-2) annealing is demonstrated. X-ray photoelectron spectra (XPS) show that the number of Ga-O bonds decreases while that of the Ga-N bonds increases, an indication of the surface native oxide removal after FG annealing. Compared with N-2 annealing, an increase of two-dimensional electron gas (2DEG) electron density with FG annealing is determined by both energy band simulation and capacitance-voltage measurement. Transmission line measurement (TLM) shows that N-2 annealing offers a lower ohmic contact resistance (R-C) while FG annealing features a lower sheet resistance (R-sheet). Herein, a FG/N-2 two-step ohmic contact annealing is developed to achieve a SS of 110 mV/dec, a transconductance (g(m)) peak of 415 mS/mm, a record low drain-induced barrier lowing (DIBL) of 65 mVN, and a record high power gain cutoff frequency (f(max)) of 270 GHz on a 50-nm InAlN/GaN HEMT on Si.

Automated summary

The article investigates the improved surface properties of InAlN/GaN HEMTs after forming gas annealing and proposes a two-step forming gas/nitrogen annealing method for ohmic contact. This method can achieve lower sheet resistance, higher two-dimensional electron gas electron density, and better device performance.