Bulk β-Ga₂O₃ with (010) and (201) Surface Orientation: Schottky Contacts and Point Defects

Abstract

Electrical properties of Schottky contacts of high work-function metals (Pd, Au, and Ni) on (010) and (201) oriented β-Ga2O3 were investigated. Current-voltage characteristics reveal that all the contacts exhibit high rectifying behavior with ideality factors as low as 1.04. However, the reverse leakage currents were lower in the (010) samples compared to the (201) ones. Thermal admittance spectroscopy confirms a main charge carrier level to be at ~0.15 eV below the conduction band edge (Ec). Secondary ion mass spectrometry indicates that Si may be responsible for this donor level. Deep level transient spectroscopy reveals four levels (E1-E4) in the upper part of the band gap, with the corresponding energy level positions at 0.56, 0.76, 1.01, and 1.48 eV below Ec.

Generation and metastability of deep level states in β-Ga2O3 exposed to reverse bias at elevated temperatures

“…The level labeled as E1 (here and in the literature) exhibits characteristics similar to those reported previously. 10,17,18 The properties of E2 observed in the HVPE sample are also consistent with the literature. 19 Both these levels are seen at low concentrations in our samples and are taken out of consideration in the rest of our analysis.…”

“…E-beam deposition of Ni was used to manufacture Schottky contacts that exhibited suitable properties for the DLTS characterization. 18 Circular Ni contacts with radii 100, 240, and 400 μm were deposited through a shadow mask on the wafers using e-beam evaporation. A stack of Ti/Al was applied to the back of the wafers to serve as an ohmic contact, also using e-beam evaporation.…”

“…Further, a fourth level was reported in EFG samples at ∼1.48 eV below E C and was labeled E4. 18 Moreover, Fe has been recognized as the cause of the most prominent level in the bulk material (E2), whereas another closely located level (E2*) was found to be generated by proton irradiation. 19 Gao et al have employed oxygen plasmas and forming gas anneals, as examples of oxidizing and reducing treatments, for the purpose of varying the intrinsic point defect balance in β-Ga 2 O 3 .…”

Electrical Properties of Vertical p‐NiO/n‐Ga2O3 and p‐ZnCo2O4/n‐Ga2O3 pn‐Heterodiodes

“…A defect level with similar activation energy was found in homoepitaxial β ‐Ga 2 O 3 thin films fabricated by metal organic chemical vapor deposition or fabricated by plasma enhanced molecular beam epitaxy . In bulk samples, a defect level with this activation energy was not detected or found by computer simulations . This is a hint that this defect commonly occurs in epitaxial β ‐Ga 2 O 3 thin films.…”

First principles study of Schottky barriers at Ga2O3(100)/metal interfaces

“…In contrast, the (100) plane is nonpolar 18 and shows good convergence. Furthermore, experiment 19 showed that the dependence on different planes is not very notable. Therefore, we construct interfaces with ten-layer (100) oriented b-Ga 2 O 3 and four-layer metal atoms.…”