Geometrical and thermal effects on mobility and analog parameters of AlGaN/GaN HEMTs on silicon substrates

Abstract

This work investigates how temperature and channel geometry affect the analog performance of AlGaN/GaN high electron mobility transistors (HEMTs) fabricated on silicon. Devices with varying lengths and widths were characterized across a temperature range from −35 °C to 25 °C. Four different methods were used to extract the carrier mobility: effective mobility (μeff) calculated from the ratio ID/(VG–VT) at low drain voltage; field-effect mobility (μFE) obtained from the transconductance in the linear regime; low-field mobility (μo) estimated from the drift–diffusion model; and peak transconductance mobility derived from the maximum value of gm. The results consistently followed the trend μeff > μFE > μo, and all mobilities showed degradation with increasing temperature due to enhanced phonon scattering. Key parameters such as threshold voltage (VT), subthreshold swing (SS), transconductance (gm), DIBL, output conductance (gD), Early voltage (VEA), and intrinsic gain (AV) were also evaluated, confirming that temperature and geometry critically influence device performance.