Abstract
With the global shortage of 3He gas, researchers worldwide are looking for alternative materials for detecting neutrons. Among the candidate materials, semiconductors are attractive because of their light weight and ease in handling. Currently, we are looking into the suitability of boron arsenide (B12As2) for this specific application. As the first step in evaluating the material qualitatively, the photo-response of B12As2 bulk crystals to light with different wavelengths was examined. The crystals showed photocurrent response to a band of 407- and 470- nm blue light. The maximum measured photoresponsivity and the photocurrent density at 0.7 V for 470 nm blue light at room temperature were 0.25 A ⋅ W−1 and 2.47 mA ⋅ cm−2, respectively. In addition to photo current measurements, the electrical properties as a function of temperature (range: 50-320 K) were measured. Reliable data were obtained for the low-temperature I-V characteristics, the temperature dependence of dark current and its density, and the resistivity variations with temperature in B12As2 bulk crystals. The experiments showed an exponential dependence on temperature for the dark current, current density, and resistivity; these three electrical parameters, respectively, had a variation of a few nA to μA, 1-100 μA ⋅ cm−2 and 7.6x105-7.7x103 Ω ⋅ cm, for temperature increasing from 50 K to 320 K. The results from this study reported the first photoresponse and demonstrated that B12As2 is a potential candidate for thermal-neutron detectors.
Highlights
The release of radioactive materials presents a real threat to homeland- and national-security
The results from this study reported the first photoresponse and demonstrated that B12As2 is a potential candidate for thermal-neutron detectors
For lights with higher wavelengths, the penetration depths are higher than the thickness of the detector and material was almost transparent to the higher wavelengths and there was no photo response
Summary
In such compound materials, neutron capture and ionization generation occur in the same media, allowing full absorption of secondary particles and, ideally, complete charge collection of the generated electrons and holes. Among all the candidate semiconductor materials, icosahedral boron arsenide (B12As2) is appealing for thermal neutrons detection due to its wide band-gap (3.20-3.47 eV)[2,3,4,5] and potentially good carrier-transport properties. This study was intended to explore, and hopefully validate, that the charge carriers in B12As2 could be activated by incident LED-energy and transported through the crystal inducing electronic signals on the electrodes of fabricated detectors that could be measured by an appropriate readout circuit
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