A nonlinear model to assess DC/AC performance reliability of submicron SiC MESFETs

A modified nonlinear model to predict direct-current (DC) and alternating-current (AC) characteristics of submicron SiC metal–semiconductor field-effect transistors (MESFETs) is presented. Such devices are normally operated under high-bias conditions, resulting in intense channel conditions and deviation from the usual device response. It has been demonstrated that, under relatively high drain bias, the Schottky barrier depletion is modified, causing the drain current to increase rapidly and thereby making the control of the Schottky barrier gate less effective. It has been observed that, when the ratio of the transconductance to the output conductance (g_m/ g_d) becomes less than unity, the device operational capabilities are drastically affected. Additionally, the small-signal intrinsic parameters of SiC MESFETs were assessed by evaluating the device Miller capacitances at various bias levels, revealing a significant increase in their magnitude at relatively high drain bias (V_ds≥ 40 V), which leads to deterioration of the high-frequency capabilities of the device, including the unity-gain frequency, f_T. Compared with the best reported model, the developed technique exhibited ∼48% improved accuracy in predicting the I–V characteristics of submicron SiC MESFETs and ∼63.5% improvement in evaluating the output conductance of the device. Thus, this technique can be employed to determine device reliability under intense operating conditions.