Role of defects in ultra-high gain in fast planar tin gallium oxide UV-C photodetector by MBE

Gunasekar, Naresh 2022. Role of defects in ultra-high gain in fast planar tin gallium oxide UV-C photodetector by MBE. Applied Physics Letters 121 (11) , 111105. 10.1063/5.0107557

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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.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Physics and Astronomy
Uncontrolled Keywords:	Deep UV photodetectors
Publisher:	American Institute of Physics
ISSN:	0003-6951
Date of First Compliant Deposit:	4 October 2022
Date of Acceptance:	22 August 2022
Last Modified:	17 Sep 2023 16:55
URI:	https://orca.cardiff.ac.uk/id/eprint/153057

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