Role of defects in ultra-high gain in fast planar tin gallium oxide UV-C photodetector by MBE
Abstract
We report ultra-high responsivity of epitaxial (SnxGa1−x)2O3 (TGO) Schottky UV-C photodetectors and experimentally identified the source of gain as deep-level defects, supported by first principles calculations. Epitaxial TGO films were grown by plasma-assisted molecular beam epitaxy on (−201) oriented n-type β-Ga2O3 substrates. Fabricated vertical Schottky devices exhibited peak responsivities as high as 3.5 ×104 A/W at −5 V applied bias under 250 nm illumination with sharp cutoff shorter than 280 nm and fast rise/fall time in milliseconds order. Hyperspectral imaging cathodoluminescence (CL) spectra were examined to find the mid-bandgap defects, the source of this high gain. Irrespective of different tin mole fractions, the TGO epilayer exhibited extra CL peaks at the green band (∼2.20 eV) not seen in β-Ga2O3 along with enhancement of the blue emission-band (∼2.64 eV) and suppression of the UV emission-band. Based on hybrid functional calculations of the optical emission expected for defects involving Sn in β-Ga2O3, VGa–Sn complexes are proposed as potential defect origins of the observed green and blue emission-bands. Such complexes behave as acceptors that can efficiently trap photogenerated holes and are predicted to be predominantly responsible for the ultra-high photoconductive gain in the Sn-alloyed Ga2O3 devices by means of thermionic emission and electron tunneling. Regenerating the VGa–Sn defect complexes by optimizing the growth techniques, we have demonstrated a planar Schottky UV-C photodetector of the highest peak responsivity.
Document Details
- Document Type
- Pub Defense Publication
- Publication Date
- Sep 12, 2022
- Source ID
- 10.1063/5.0107557
Entities
People
- Akhil Mauze
- Daniel A. Hunter
- Feng Wu
- Isa Hatipoglu
- James S. Speck
- Joel B Varley
- Martin S. Williams
- Naresh Gunasekar
- Partha Mukhopadhyay
- Paul R. Edwards
- Robert Martin
- Winston V. Schoenfeld
- Ymir Kalmann Frodason
Organizations
- Cardiff University
- Engineering and Physical Sciences Research Council
- Lawrence Livermore National Laboratory
- Research Council of Norway
- University of Central Florida
- University of Oslo
- University of Strathclyde
- Şırnak University