For the first time, samples of particle detectors based on high-purity GaAs epilayers with an active area of 25 and 80 mm 2 and an ultra-thin Pt Schottky barrier were fabricated for use in the spectrometry of charged particles and their operating characteristics were studied. The obtained FWHM of 14.2 (for 25 mm 2 detector) and 15.5 keV (for 80 mm 2 detector) on the 5.499 MeV line of 238 Pu is at the level of silicon spectrometric detectors. It was found that the main component that determines the energy resolution of the detector is a fluctuation in the number of collected electron–hole pairs. This allows us to state that the obtained energy resolution is close to the limit for VPE GaAs.

GaAs detectors with an ultra-thin Schottky contact for spectrometry of charged particles

We have examined semi-insulating (SI) GaAs detectors with high density polyethylene (HDPE) conversion layer by a mono-energetic neutrons with kinetic energy of 16.755 MeV generated by a deuterium—tritium nuclear reaction. First, the influence of HDPE layer thickness on the relative detection efficiency of fast neutrons was studied. The MCNPX (Monte Carlo N-particle eXtended) code has been used to support the analysis of the experiment. The theoretical optimum thickness of the conversion layer was determined to 1.9 mm using the MCNPX code. The HDPE conversion layers of various thicknesses, in the range from 50 μ m to 3200 μ m, were glued on the top Schottky contact of SI GaAs detector in the experiment. The neutron detection efficiency was evaluated from measured spectra and compared to results from simulations. The experimental data showed very good agreement with simulation results. Then the effect of active detector thickness modified by detector reverse bias on neutron detection efficiency was studied. Finally, the effect of the angle of irradiation on neutron detection efficiency was evaluated exhibiting decreasing tendency with increasing deviation from perpendicular direction of impinging neutrons.

http://iopscience.iop.org/article/10.1088/1748-0221/11/12/C12002/pdf

Semi-insulating GaAs based detector of fast neutrons produced by D-T nuclear reaction

Surface-barrier structures based on thin high-purity GaAs epilayers with a polyethylene converter were studied as fast neutron detectors. A continuous Schottky barrier with a large area of 5 × 5 mm2 to the high-purity GaAs epilayers was fabricated using a Pt/TiN/Au metallization system. Results of measurement of electric parameters and α-particle spectra are presented. The fast neutron spectra from the 241Am-Be source measured by the recoil proton method for various thicknesses of the polyethylene converter and various operating biases are shown as well. The proposed detectors have shown high neutron detection efficiency of 1.3010−3 puls./neutr. and an acceptable signal-to-background ratio (at level of 50) as well as the capability to operate efficiently without any external bias.

http://iopscience.iop.org/article/10.1088/1748-0221/10/01/C01021/pdf

Fast neutron detector based on surface-barrier VPE GaAs structures

The AlxGa1-xAs / GaAs photosensitive heterostructures were grown by molecular beam epitaxy. On their basis the discrete photodiodes (PD) and phototransistors (PT) operating in the visible (0.4–0.7 μm) wavelength range and having photosensitive area diameters of 1.5 mm and 180 pm correspondingly were created. The current-voltage and spectral characteristics of discrete PD and PT were measured and analyzed. Distinctive features of the proposed photodetectors are a high monochromasy with the maximal sensitivity of 0.13 A/W at λ = 530-570 nm and a low dark current of 4.7 nA and 530 pA at 5 V reverse bias for PD and PT correspondingly.

https://iopscience.iop.org/article/10.1088/1742-6596/586/1/012018/pdf

AlGaAs/GaAs photodetectors for detection of luminescent light from scintillators

Fast neutron detectors with an active area of 80 mm2 based on surface-barrier VPE GaAs structures were fabricated and tested. Polyethylene with density of 0.90 g/cm3 was used as a converter layer. The recoil-proton surface-barrier sensor was fabricated on high purity VPE GaAs epilayers with a thickness of 50 μm. The neutron detection efficiency measured with a 241Am-Be source was 1.30 10−3 puls./neutr. for the PE converter thickness of 670 μm. The signal-to-gamma-background ratio was at the level of 50. Simulation of the detector characteristics with Geant4 toolkit has showed good correlation with the experimental data and allowed to estimate the maximal theoretical detection efficiency of the detector which is determined by the PE converter and equals to 1.37 10−3 puls./neutr. The difference between the measured and simulated values of the detection efficiency is due to the fact that the events with energies below 0.5 MeV were not taken into account during the measurements.

https://iopscience.iop.org/article/10.1088/1748-0221/11/12/C12005/pdf

Characterization and simulation of fast neutron detectors based on surface-barrier VPE GaAs structures with polyethylene converter

The electrical characteristics of Ti and Pt Schottky contacts to epitaxial n-GaAs layers with the charge-carrier concentration <1012 cm−3 for detectors of particles and X- or γ-ray photons are studied. It is shown that it is preferable to use a diffusion-based theory of charge transport in calculations of the parameters of Schottky contacts to thick high-resistivity lightly compensated GaAs layers. The calculated barrier heights were 0.84 and 0.87 eV for the Ti and Pt contacts, respectively. The fabricated samples of the surface-barrier detectors featured a linear response in the studied range of energies from 6 to 140 keV for γ-ray photons and from 4 to 8 MeV for α particles; the efficiency of charge collection was close to 100% and the energy resolution was high at room temperature.

Schottky contacts to high-resistivity epitaxial GaAs layers for detectors of particles and X- or γ-ray photons

Samples of nuclear detectors which represent matrices of p-i-n diodes were fabricated based on undoped gallium arsenide epitaxial layers by ion implantation technology The detectors have a size of the active area of 04×04 and 09×09 cm2 Electrical characteristics of fabricated detectors and results of measurements of fast neutrons spectra of 241Am-Be source by the recoil protons method are discussed

Nuclear radiation detectors based on a matrix of ion-implanted p-i-n diodes on undoped GaAs epilayers

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Fast neutron detector based on surface-barrier VPE GaAs structures

Schottky contacts to high-resistivity epitaxial GaAs layers for detectors of particles and X- or γ-ray photons

Nuclear radiation detectors based on a matrix of ion-implanted p-i-n diodes on undoped GaAs epilayers