30 μm thick GaAs X-ray p+-i-n+ photodiode grown by MBE

Lioliou, G, Poyser, C L, Butera, S, Campion, R P, Kent, A J and Barnett, A M (2019) 30 μm thick GaAs X-ray p+-i-n+ photodiode grown by MBE. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment. ISSN 0168-9002 (Accepted)

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Abstract

A GaAs p+-i-n+ photodiode detector with a 30 μm thick i layer and a 400 μm diameter was processed using standard wet chemical etching from material grown by molecular beam epitaxy. The detector was characterized for its electrical and photon counting X-ray spectroscopic performance at temperatures from 60°C to -20 °C. The leakage current of the detector decreased from 1.247 nA ± 0.005 nA (= 0.992 μA/cm2 ± 0.004 μA/cm2) at 60 °C to 16.0 pA ± 0.5 pA (= 12.8 nA/cm2 ± 0.4 nA/cm2) at -20 °C, at the maximum investigated applied reverse bias, -100 V (corresponding to an applied electric field of 33 kV/cm). An almost uniform effective carrier concentration of 7.1 × 1014 cm-3 ± 0.7 × 1014 cm-3 was found at distances between 1.7 μm and 14 μm below the p+-i junction, which limited the depletion width to 14 μm ± 1 μm, at the maximum applied reverse bias (-100 V). Despite butterfly defects having formed during the epitaxial growth, 55 Fe X-ray spectra were successfully obtained with the detector coupled to a custom-made charge-sensitive preamplifier; the best energy resolution (Full Width at Half Maximum at 5.9 keV) improved from 1.36 keV at 60 °C to 0.73 keV at -20 °C. Neither the leakage current nor the capacitance of the GaAs detector were found to be the limiting factors of the energy resolution of the spectroscopic system; noise analysis at 0 °C and -20 °C revealed that the dominant source of noise was the quadratic sum of the dielectric and incomplete charge collection noise.

Item Type: Article
Additional Information: A.M.B. acknowledges funding from the Leverhulme Trust, United Kingdom, in the form of a 2016 Philip Leverhulme Prize
Keywords: Gallium Arsenide; GaAs; X-ray spectroscopy; wide bandgap; high temperature
Schools and Departments: School of Engineering and Informatics > Engineering and Design
Research Centres and Groups: Space Research Group
Depositing User: Lucy Arnold
Date Deposited: 11 Sep 2019 08:54
Last Modified: 11 Sep 2019 09:00
URI: http://sro.sussex.ac.uk/id/eprint/86098

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Radioisotope MicrobatteriesG1951STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCILST/P001815/1