High performance titanium nitride sub-100 nm rectifying contact, deposited by sputtering on AlGaN/GaN high electron mobility transistors, shows a reverse leakage current as low as 38 pA/mm at VGS = -40 V and a Schottky barrier height of 0.95 eV. Based on structural characterization and 3D simulations, it is found that the polarization gradient induced by the gate metallization forms a P-type pseudo-doping region under the gate between the tensile surface and the compressively strained bulk AlGaN barrier layer. The strain induced by the gate metallization can compensate for the piezoelectric component. As a result, the gate contact can operate at temperatures as high as 700 °C and can withstand a large reverse bias of up to -100 V, which is interesting for high-performance transistors dedicated to power applications

An analysis of frequency dispersion in capacitance and conductance of gate-source contact of AlGaN/GaN HEMT was performed. Capacitance and conductance were measured at temperatures varying from 83 K to 370 K with bias voltage maintained at 0 V. In order to characterize trap states the conductance method was used considering series resistance. Hence, the parallel conductance G p and capacitance C p were calculated, and consequently interface trap density D it and time constant t are deduced. The analysis is performed assuming a continuum of levels yielding to a trap density of approximately 10 +12 cm −2 eV −1 and a time constant varying between 1 µs and 3 ms. Activation energies and capture cross sections of three trap levels were deduced and their values were respectively ( E a1 = 0.201 eV, σ n1 = 4.992 × 10 −18 cm 2 ), ( E a2 = 0.053 eV, σ n2 = 2.585 × 10 −21 cm 2 ), ( E a3 = 0.121 eV, σ n3 = 1.256 × 10 −20 cm 2 ). An electrical model was established with two levels of traps at AlGaN/GaN interface and one level located in barrier AlGaN surface.

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