The temperature dependent photoresponse of planar photodetectors fabricated on β-Ga2O3 films grown on Al2O3 by metalorganic chemical vapor deposition to 254 nm wavelength, and blindness to 365 nm light, are reported over the range of 25-350 °C. Ohmic contacts were formed by Si-implantation and annealing at 900 °C, followed by deposition of Ti/Au metallization. The photocurrent induced by 254 nm illumination increased monotonically with temperature, from ∼2.5 × 10-7 A at 25 °C to ∼2.2 × 10-6 A at 350 °C at a fixed 254 nm light intensity of 760 μW/cm2. The photosensitivity decreases at high temperatures in many photoconductors (thermal quenching), in sharp contrast to the photosensitivity increase with high temperatures in this study. This is ascribed to the presence of states in the gap of Ga2O3, whose presence was proven by exposure to below band-gap energy. In this case, the current still increased due to the presence of defect levels in the band gap and the generation of photocurrent is due to a transition between the valence or conduction band and impurity or defect levels within the band gap. The temperature dependent photo-to-dark current ratio for this wavelength was 328 at room temperature and decreased to ∼9 at 350 °C. The responsivity increased from 5 to 36 A/W over this temperature range, with corresponding external quantum efficiencies of 2.5 × 103 % at 25 °C and 1.75 × 104 % at 350 °C. Similarly large numbers reported for Ga2O3 photodetectors have previously been ascribed to carrier multiplication effects.
|Journal||Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics|
|Publication status||Published - 2016 Jul 1|
Bibliographical noteFunding Information:
The research at University of Florida was supported by DTRA (Contract No. HDTRA11-1-0020), while that at Korea University was supported by the New and Renewable Energy Core Technology Program of the Korea Institute of Energy Technology Evaluation and Planning (KETEP), granted financial resource from the Ministry of Trade, Industry and Energy (No. 20153030012110). Research at the U.S. Naval Research Laboratory was supported by the Office of Naval Research.
© 2016 American Vacuum Society.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Process Chemistry and Technology
- Surfaces, Coatings and Films
- Electrical and Electronic Engineering
- Materials Chemistry