AlGaN/GaN-based HEMT on SiC substrate for microwave characteristics using different passivation layers

In this paper, a new gate-recessed AlGaN/GaN-based high electron mobility transistor (HEMT) on SiC substrate is proposed and its DC as well as microwave characteristics are discussed for Si₃N₄ and SiO₂ passivation layers using technology computer aided design (TCAD). The two-dimensional electron gas (2DEG) transport properties are discussed by solving Schr?dinger and Poisson equations self-consistently resulting in various subbands having electron eigenvalues. From DC characteristics, the saturation drain currents are measured to be 600?mA/mm and 550?mA/mm for Si₃N₄ and SiO₂ passivation layers respectively. Apart from DC, small-signal AC analysis has been done using two-port network for various microwave parameters. The extrinsic transconductance parameters are measured to be 131.7?mS/mm at a gate voltage of V _gs?= ?0.35?V and 114.6?mS/mm at a gate voltage of V _gs?= ?0.4?V for Si₃N₄ and SiO₂ passivation layers respectively. The current gain cut-off frequencies (f _t) are measured to be 27.1?GHz and 23.97?GHz in unit-gain-point method at a gate voltage of ?0.4?V for Si₃N₄ and SiO₂ passivation layers respectively. Similarly, the power gain cut-off frequencies (f _max) are measured to be 41?GHz and 38.5?GHz in unit-gain-point method at a gate voltage of ?0.1?V for Si₃N₄ and SiO₂ passivation layers respectively. Furthermore, the maximum frequency of oscillation or unit power gain (MUG = 1) cut-off frequencies for Si₃N₄ and SiO₂ passivation layers are measured to be 32?GHz and 28?GHz respectively from MUG curves and the unit current gain, ?O?h ₂₁??O?=?1 cut-off frequencies are measured to be 140?GHz and 75?GHz for Si₃N₄ and SiO₂ passivation layers respectively from the abs ?O?h ₂₁??O curves. HEMT with Si₃N₄ passivation layer gives better results than HEMT with SiO₂ passivation layer.