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Enhancement‐Mode AlGaN/GaN Vertical Trench Metal–Insulator–Semiconductor High‐Electron‐Mobility Transistors with a High Drain Current Fabricated Using the AlGaN Regrowth Technique
Author(s) -
Yamamoto Akio,
Kanatani Keito,
Yoneda Norifumi,
Asubar Joel T.,
Tokuda Hirokuni,
Kuzuhara Masaaki
Publication year - 2020
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201900622
Subject(s) - materials science , optoelectronics , trench , transistor , metalorganic vapour phase epitaxy , epitaxy , semiconductor , reactive ion etching , annealing (glass) , etching (microfabrication) , layer (electronics) , voltage , nanotechnology , electrical engineering , composite material , engineering
Herein, the first successful fabrication of enhancement (E)‐mode AlGaN/GaN vertical trench metal–insulator–semiconductor (MIS) high‐electron‐mobility transistors (HEMTs) using n + ‐GaN/p‐GaN/n − ‐GaN epistructures on free‐standing n + substrates is reported. A trench with smooth semipolar planes (sidewalls) with angles of 45° and 135° from the c ‐plane is formed by reactive ion etching. Using metalorganic vapor‐phase epitaxy, a uniform thickness of the AlGaN layer is regrown in the trench. Devices fabricated without Mg activation treatment for p‐GaN show depletion (D)‐mode operation. The operation mode is changed from D to E when Mg activation annealing temperature exceeds 700 °C. A high drain current ( I D ) ≥ 0.8 A mm −1 is obtained in the devices with a relatively low Mg concentration (≤1 × 10 18 cm −3 ), whereas a threshold voltage ( V TH ) as high as 22 V is obtained in the devices with a high Mg concentration (5 × 10 18 cm −3 ). The poorly controlled V TH with doped Mg concentration is discussed from the viewpoint of dehydrogenation of the p‐GaN layer.