Enhancement-mode β-Ga2O3 U-shaped gate trench vertical MOSFET realized by oxygen annealing

Abstract

Vertical metal–oxide–semiconductor field effect transistor (MOSFET) is essential to the future application of ultrawide bandgap β-Ga2O3. In this work, we demonstrated an enhancement-mode β-Ga2O3 U-shaped gate trench vertical metal–oxide–semiconductor field effect transistor (UMOSFET) featuring a current blocking layer (CBL). The CBL was realized by high-temperature annealing under oxygen ambient, which provided electrical isolation between the source and drain electrodes. The CBL thicknesses of different annealing temperatures were derived from C–V measurements and the Fermi level position of the sample surfaces of different annealing temperature was characterized by x-ray photoelectron spectroscopy measurements, indicating good process controllability. Furthermore, photoluminescence spectra were measured to study the effect of oxygen annealing. The fabricated UMOSFET showed normally off with a Vth of 11.5 V, an on-state resistance of 1.48 Ω cm2, a maximum on-state current of 11 A/cm2, an on–off ratio of 6 × 104, and a three-terminal breakdown voltage over 100 V. This work paves a way to form a CBL and broadens the design space for high-power β-Ga2O3 vertical transistors.

Bandgap Engineering and Oxygen Vacancy Defect Electroactivity Inhibition in Highly Crystalline N-Alloyed Ga2O3 Films through Plasma-Enhanced Technology

“…In contrast to third-generation semiconductors, such as GaN and SiC, β-Ga 2 O 3 possesses several advantages, including a wider bandgap, a higher breakdown field strength, and the ability to easily grow high-quality single crystals in large sizes. − As a result, β-Ga 2 O 3 -based photodetectors have demonstrated exceptional sensitivity and responsivity in the deep-ultraviolet (DUV) range, making them ideal for DUV sensing and imaging applications . Moreover, β-Ga 2 O 3 -based transistors have exhibited remarkable electron mobility, which makes them highly suitable for high-frequency and high-power electronic applications. − However, during the growth process, Ga 2 O 3 inevitably introduces oxygen vacancies, which pose significant challenges to intrinsic carrier regulation, − p-type doping, − and the formation of stable Schottky contacts. , For instance, the presence of oxygen vacancies leads to persistent photoconductivity (PPC) effects, resulting in unexpected photoconductive gains but slow response speed due to trapping effects. − Furthermore, the oxygen vacancy defects (V O ) on the surface of Ga 2 O 3 cause electrons to be transported through tunneling puncture effects that result in the high reverse leakage current of transistors. − …”

Phase Stabilized MOCVD Growth of β‐Ga2O3 Using SiOx on c‐Plane Sapphire and AlN/Sapphire Template

“…The Ga 2 O 3 sample A2 was annealed at 900-1200 °C for 30 min in the same MOCVD reactor in which it was grown under equal amounts of N 2 and O 2 flows (1000 sccm) at a pressure of 50 Torr in a similar way described in the literature. [21,22,29]…”

The origin of twins in the growth of the (100) plane of a β-Ga2O3 crystal using EFG

“…3 The performance of β-Ga 2 O 3 crystals can also be tuned by different dopants, such as Sn and Si to increase the carrier concentration in the crystal, Fe and Mg to obtain an insulating substrate, and Ti, to obtain the laser output. [4][5][6][7] These good qualities allow β-Ga 2 O 3 crystals to be used in semiconductor lasers, 8 high-temperature gas sensors, 9 deep UV detectors, 10 scintillation detectors, 11 field effect transistors, 12,13 Schottky barrier diodes, [14][15][16] and transparent conductive electrodes. 17 β-Ga 2 O 3 crystals can be grown by melt methods, such as the floating zone (FZ), [18][19][20] Czochralski (CZ), [21][22][23][24] vertical Bridgman (VB), [25][26][27] and edge-defined film-fed growth (EFG) methods.…”