Degenerate GaN source–drain AlN/Al<i>x</i>Ga1−<i>x</i>N/AlN high electron mobility transistors with a high breakdown electric field reaching 6.0 MV/cm
Kohei Ueno, Ryota Maeda, Takao Kozaka, Hiroshi Fujioka
Abstract
This study presents a comprehensive analysis of the structural and electrical properties of degenerate GaN source–drain AlN/AlxGa1−xN/AlN high electron mobility transistors (HEMTs) fabricated using low-temperature pulsed sputtering epitaxial growth. The investigation encompassed a range of Al compositions (0.3 ≤ x ≤ 0.7). Partially relaxed AlN/Al0.3Ga0.7N/AlN HEMTs exhibited a high drain current (ID = 580 mA/mm) and low contact resistance (RC = 0.30 Ω mm). Fully strained AlN/Al0.5Ga0.5N/AlN HEMTs achieved a balance between low on-resistance and high breakdown voltage, resulting in the highest lateral figure of merit of 319 MW/cm2 in this study. For x = 0.6, a peak breakdown electric field of 6.0 MV/cm was observed in a device with a short gate–drain distance. These results show the great potential of the low-temperature sputtering epitaxial growth process of AlN/AlxGa1−xN/AlN double heterostructure HEMTs with the degenerate regrowth GaN source–drain for the next-generation ultrahigh BV power electronics.