Research on RF performance of GaN HEMT with graded Al composition AlGaN back-barrier

In this paper, we apply AlGaN back-barrier with graded Al composition to effectively improve the RF performance of GaN high electron mobility transistor (HEMT). Simulation results demonstrate that compared with GaN HEMT with fixed Al composition AlGaN back-barrier, graded AlGaN back-barrier HEMT has lower gate capacitance and better two-dimensional electron gas (2DEG) confinement. Its cut-off frequency ($f_t$) and maximum oscillation frequency ($f_{\max }$) reach 100 GHz and 179.8 GHz, respectively, an increase of 12.1 GHz and 42.9 GHz. Due to the lower power supply, graded AlGaN back-barrier HEMT also significantly improves the power added efficiency (PAE) compared with HEMT without back-barrier, increasing 20 %. Moreover, it is found that graded AlGaN back-barrier HEMT has better large-signal performance than fixed AlGaN back-barrier HEMT for the better electron confinement.