Optimization of GaN HEMTs with ScAlN Barrier for High 2DEG Density and Low on-Resistance

ScAlN is a novel barrier material for GaN-based high electron mobility transistors (HEMTs), with the potential to provide extremely high carrier densities and ultra-low on-resistance in RF and switching power supply applications. In this work, we simulate the density of two-dimensional electron gas (2DEG), electron mobility and on-resistance in GaN HEMT structures with a ScAlN barrier using an advanced mobility modeling framework. We outline the advantages of a ScAlN barrier device by comparing it to an AIGaN barrier HEMT, where we obtain a 2.44 times higher 2DEG sheet density and an improvement in on-resistance by a factor of 2.26. Thereafter, we optimize the barrier Sc-content and thickness to achieve a minimal room-temperature on-resistance of 130
$\Omega/\square$
, with a 2DEG density close to
$5.10^{13} \ \text{cm}^{-2}$
. Furthermore, we examine the impact of GaN and AlN interlayers (ILs), which are commonly added between the ScAlN barrier and GaN channel, and find that a thinner GaN IL and a thicker AlN IL is preferred for high 2DEG density and low on-resistance, provided that the strain-induced dislocations for AlN layers close to their critical thickness do not degrade the 2DEG mobility. The study reveals the most important factors determining the on-resistance, thereby offering guidance for the design of future ScAlN barrier HEMTs.