| AVS 64th International Symposium & Exhibition | |
| Electronic Materials and Photonics Division | Thursday Sessions |
| Session EM+NS-ThA |
| Session: | Wide and Ultra-wide Band Gap Materials for Electronic Devices: Growth, Modeling, and Properties |
| Presenter: | Patrick Carey IV, University of Florida |
| Authors: | P. Carey IV, University of Florida F. Ren, University of Florida D. Hays, University of Florida B. Gila, University of Florida S.J. Pearton, University of Florida S. Jang, Dankook University, South Korea A. Kuramata, Tamura Corporation, Japan |
| Correspondent: | Click to Email |
Band alignments for Al2O3, LaAl2O3 (LAO), Aluminum Zinc Oxide (AZO), and Indium Tin Oxide (ITO) with bulk β-Ga2O3 were determined by X-ray Photoelectron Spectroscopy. β-Ga2O3 is a direct band gap, ~4.9 eV, semiconductor, it has a very high theoretical breakdown electric field (~8 MV/cm), and is suitable for high power electronics in industrial, military applications, deep-UV photodetectors for a cut-off wavelength of 280 nm, and high temperature gas sensors. Ohmic contact with low contact resistance and gate oxides with low leakage current are essential for fabricating high performance base Ga2O3 electronic and optical devices. Since Ga2O3 has a wide energy bandgap, it is difficult to form low resistance Ohmic contact with conventional metal contact. ITO and AZO were found to have a conduction band offset of gap of -0.32 and -0.79 eV, respectively, which can be used as an intermediate layers between the metal contact and Ga2O3 to reduce contact resistance on Ga2O3-based devices. For wider energy band oxides, for use as gate oxides, sputtered LAO, atomic layer deposited (ALD) and rf-magnetron sputtered Al2O3 were employed. LAO was found to have a bandgap of 6.5 eV, a valence band offset of -0.21 eV, and a conduction band offset of 2.01 eV. LAO has a type II alignment and would provide excellent electron confinement, but no barrier for hole transport. Al2O3 was found to have a bandgap of 6.9 eV regardless of preparation method. However, the deposition method affected the band alignment. For ALD Al2O3, it has a has a nested (type I) gap alignment with a valence band offset of 0.07eV and a conduction band offset of 2.23 eV. While for sputtered Al2O3 on the same Ga2O3, there is a type II alignment with a valence band offset of -0.86 eV and a conduction band offset of 3.16 eV. The conduction band offsets in either case are large and provide excellent electron confinement, but the valence band offsets are smaller than desirable for limiting hole transport.