A Comparative Study on the Electrical Properties of Vertical ( $\bar{\sf2}01$ ) and (010) $\beta$ -Ga2O3 Schottky Barrier Diodes on EFG Single-Crystal Substrates

This paper reports a comprehensive study on the anisotropic electrical properties of vertical (2̅01) and (010) β-Ga
₂
O
₃
Schottky barrier diodes (SBDs). The devices were fabricated on single-crystal substrates grown by an edge-defined film-fed growth method. The temperature-dependent current-voltage (I-V) and capacitance-voltage (C-V) characteristics were systematically measured, analyzed, and compared. The (2̅01) and (010) SBDs exhibited on-resistances (R
_ON
) of 0.56 and 0.77 mQ · cm
²
, turn-ON voltages (V
_ON
) of 1.0 and 1.3 V, Schottky barrier heights (SBHs) of 1.05 and 1.20 eV, electron mobilities of 125 and 65 cm
²
/(V · s), respectively, with an on-current of ~1.3 kA/cm
²
and on/off ratio of ~10
⁹
. The (010) SBD had a larger VON and SBH due to anisotropic surface properties (i.e., surface Fermi level pinning and band bending), as supported by X-ray photoelectron spectroscopy measurements. Temperature-dependent I-V also revealed the inhomogeneous nature of the SBH in both devices, where the (2̅01) SBD showed a more uniform SBH distribution. The homogeneous SBH was also extracted: 1.33 eV for the (2̅01) SBD and 1.53 eV for the (010) SBD. The reverse leakage current of the devices was well described by the two-step trap-assisted tunneling model and the 1-D variable range hopping conduction model. The (2̅01) SBD showed a larger leakage current due to its lower SBH and/or smaller activation energy, and thus a smaller breakdown voltage. These results indicate that the crystalline anisotropy of β-Ga
₂
O
₃
can affect the electrical properties of vertical SBDs and should be taken into consideration when designing β-Ga
₂
O
₃
electronics.