Ka Band GaN MIS-HEMT with ALD-SiN Gate Dielectric and Lp-SiN Passivation Layer

In this paper, Lower pressure SiN (LP-SiN)and atomic layer deposition SiN (ALD-SiN) is developed for fabrication of ka-band AlGaN/GaN metal insulator semiconductor (MIS) high electron mobility transistors (HEMTs). Lp-SiN layer serves as a passivation layer and offers the benefit of reducing leakage. On the other hand, the 5 nm ALD-SiN layer functions as both a gate-dielectric and a passivation layer for the inner wall of the gate-trench. The performance of the device is significantly improved. With a
$0.15- \mu \mathbf{m}$
T-gate fabrication technology, a high power-gain cutoff frequency
$f_{\text{MAX}}$
of 157 GHz has been achieved. The AlGaN/GaN MIS-HEMT exhibits a high power-added efficiency (PAE) of 49.7% at 30 GHz in a continuous-wave mode with a power density of
$5.90\ \mathbf{W}/\mathbf{mm}$
.