Trap characterization in AlGaN/GaN HEMT by analyzing frequency dispersion in capacitance and conductance

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 (Δ E a 1 = 0.201 eV, σ n 1 = 4.992 × 10 −18 cm 2 ), (Δ E a 2 = 0.053 eV, σ n 2 = 2.585 × 10 −21 cm 2 ), (Δ E a 3 = 0.121 eV, σ n 3 = 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. Copyright © 2010 John Wiley & Sons, Ltd.