A Novel LG = 40 nm AlN-GDC-HEMT on SiC Wafer With fT/IDS,peak of 400 GHz/3.18 mA/mm for Future RF Power Amplifiers

In this work, we report the RF/DC performance of novel AlN/GaN/Graded-AlGaN/GaN double-channel HEMT (AlN-GDC-HEMT) on SiC wafer for the first time. The study compares the performance between conventional AlGaN/GaN/Graded-AlGaN/GaN double-channel HEMT (AlGaN-GDC-HEMT) and the AlN-GDC-HEMT. Two quantum wells are formed in both devices, leading to distinct double peak features in transconductance and cut-off frequency plots, highlighting efficient inter-channel connection behavior. The study investigates the relative performance of AlN-GDC-HEMT and AlGaN-GDC-HEMT, exploring the influence of gate recess length (L
$_{\mathrm {R}}$
) and top barrier thickness. Additionally, the scaling behavior of the HEMTs is examined with varying gate lengths (L
$_{\mathrm {G}}$
). Furthermore, the impact of gate engineering and lateral scaling on both devices’ DC/RF behavior is explored. Extensive comparative analysis shows that the AlN-GDC-HEMT outperforms the conventional AlGaN-GDC-HEMT, mainly attributed to AlN’s higher polarization (spontaneous) density and its wider bandgap. The optimized AlN-GDC-HEMT with L
$_{\mathrm {G}} =40$
nm, L
$_{\mathrm {GS}} =250$
nm, and L
$_{\mathrm {GD}} =400$
nm exhibits superior performance resulting in transconductance (G
$_{\mathrm {M}}$
) values of 203.1 and 787.5 mS/mm at two peaks, an I
$_{\mathrm {DS\_peak}}$
of 1.97 A/mm, I
$_{\mathrm {DS\_sat}}$
of 3.18 A/mm, and the highest fT derived from the left and right peaks was 285.1 and 416.8 GHz, respectively. The promising results from this first investigation indicate the potential and applicability of AlN-GDC-HEMTs in future RF power amplifiers.