Analysis of Small-Signal Parameters of 2-D Modfet with Polarization Effects for Microwave Applications

Abstract

An improved analytical two dimensional (2-D) model for AlGaN/GaN modulation doped field effect transistor (MODFET) has been developed. The model is based on the solution of 2-D Poisson's equation.The model includes the spontaneous and piezoelectric polarization effects. The effects of field dependent mobility, velocity saturation and parasitic resistances are included in the current voltage characteristics of the developed two dimensional electron gas (2-DEG) model. The small-signal microwave parameters have been evaluated to determine the output characteristics, device transconductance and cut-off frequency for 50 nm gate length. The peak transconductance of 165mS/mm and a cut-off frequency of 120 GHz have been obtained. The results so obtained are in close agreement with experimental data, thereby proving the validity of the model.

An analytical model for the current voltage characteristics of GaN-capped AlGaN/GaN and AlInN/GaN HEMTs including thermal and self-heating effects

“…The threshold voltage Vth is defined as the applied gate voltage for which the channel is completely depleted, and is considered as the minimum potential in the channel [23]. The dependence of Vth on temperature and Al mole fraction m (m = 0.32 for structure A, and m = 0.83 for B), including the effects of both spontaneous and piezoelectric charge polarization, is given by the following expressions: without cap [24]:…”

Microwave Analysis for Two-Dimensional C-V and Noise Model of AlGaN/GaN MODFET

“…For a given aluminum mole fraction, there is a certain critical thickness of barrier layer. Equation (6) shows that the device remains completely strained for Al content up to 38% and fully relaxed for Al content greater than 67% for thickness range of 200-400Å.…”

“…Capacitancevoltage characteristics are widely used as a diagnostic tool for semiconductor. The C-V characteristics also provide more information about the nonlinearity of the device for the large signal models [3][4][5][6]. Low noise HEMTs are promising devices for millimetre wave due to their excellent high frequency and low noise performances.…”