Numerical simulation of the impact of surface traps on the performance of InP-based high electron mobility transistors

In this paper, the DC and RF characteristics of our own InP-based HEMTs were investigated comprehensively with surface traps concentration varying among 0 cm−2, 1 × 1012 cm−2, 3 × 1012 cm−2. Reasonable physical models were used to describe the device performances, including hydrodynamic transport model, density gradient model, recombination models and so on. Moreover, surface Shockley–Read–Hall model and improved Possion's equation were introduced to implement for the impact of surface traps. The DC and RF characteristics have shown compatible trends between computation and experiment. With the increasing surface traps concentration over the gate-recess region, the channel current, transconductance, current gain cut-off frequency (fT) and maximum oscillation frequency (fmax) exhibit apparent decrease trends. The observed obvious changes of the DC and RF properties with surface traps could be accounted for carrier sheet density reduction, which resulted from the surface potential modulated by negatively charged surface traps. Additionally, the charged surface traps could deplete the electrons in channel region, which leads to an increase in channel sheet resistance, and thus, further decreasing the fmax.