A summary is presented of the present status of several compound semiconductor radiation detectors, including detectors fabricated from GaAs, HgI2, CdTe, Cd1−xZnxTe and PbI2

Room-temperature compound semiconductor radiation detectors

Detection of neutrons, at high total efficiency, with greater resolution in kinetic energy, time and/or real-space position, is fundamental to the advance of subfields within nuclear medicine, high-energy physics, non-proliferation of special nuclear materials, astrophysics, structural biology and chemistry, magnetism and nuclear energy. Clever indirect-conversion geometries, interaction/transport calculations and modern processing methods for silicon and gallium arsenide allow for the realization of moderate- to high-efficiency neutron detectors as a result of low defect concentrations, tuned reaction product ranges, enhanced effective omnidirectional cross sections and reduced electron–hole pair recombination from more physically abrupt and electronically engineered interfaces. Conversely, semiconductors with high neutron cross sections and unique transduction mechanisms capable of achieving very high total efficiency are gaining greater recognition despite the relative immaturity of their growth, lithographic processing and electronic structure understanding. This review focuses on advances and challenges in charged-particle-based device geometries, materials and associated mechanisms for direct and indirect transduction of thermal to fast neutrons within the context of application. Calorimetry- and radioluminescence-based intermediate processes in the solid state are not included.

https://iopscience.iop.org/article/10.1088/0953-8984/22/44/443201/pdf

The physics of solid-state neutron detector materials and geometries

Particle detectors made from artificial diamond have great promise for future experiments in particle physics because they are far less vulnerable to radiation damage than any other detector type. We review the history of diamond detectors and describe their current state of development. We also discuss the evidence which proves the resistance of these detectors to damage by various forms of incident radiation.

https://iopscience.iop.org/article/10.1088/0034-4885/63/8/203/pdf

Diamond detectors in particle physics

In recent papers, we have investigated, within the context of the RD-8 experiment, the behaviour as a function of bias of the active region of particle detectors made by Alenia SpA on semi-insulating liquid encapsulated Czochralski gallium arsenide: the active region width depends linearly on the bias voltage. The diodes were found to break down as soon as the field reached the back ohmic contact. This suggested that the ohmic contact was injecting holes into the diode, therefore we have decided to develop a new, non-injecting, non-alloyed ohmic contact. This new contact allows us to go far beyond, five times, the voltage bias necessary to have a fully active detector. The higher voltage reached by the detectors helps us improve the charge collection efficiency, up to more than 95% for alphas and more than 90% for beta (mips) particles and X-rays, giving a more stable operation of the detectors. For the first time we can explore the characteristics of a GaAs detector beyond the voltage needed for it to be completely active.

Performance of a new ohmic contact for GaAs particle detectors

High-purity epitaxial GaAs 10 B-coated thermal neutron detectors advantageously operate at room temperature without externally applied voltage. Sample detectors were systematically irradiated at fixed grid locations near the core of a 2 MW research reactor to determine their operational neutron dose threshold. Reactor pool locations were assigned so that fast and thermal neutron fluxes to the devices were similar. Neutron fluences ranged between 10 11 and 10 14  n/cm 2 . GaAs detectors were exposed to exponential fluences of base ten. Ten detector designs were irradiated and studied, differentiated between p–i–n diodes and Schottky barrier diodes. The irradiated 10 B-coated detectors were tested for neutron detection sensitivity in a thermalized neutron beam. Little damage was observed for detectors irradiated at neutron fluences of 10 12  n/cm 2 and below, but signals noticeably degraded at fluences of 10 13  n/cm 2 . Catastrophic damage was apparent for neutron fluences of 10 14  n/cm 2 . Comparison studies also included semi-insulating bulk GaAs thermal neutron detectors. It was observed that the SI bulk GaAs Schottky barrier detectors sustained the highest fluences prior to device failure. The main cause of detector failure was determined to result from the 10 B(n,α) 7 Li reaction product damage.

The effect of incremental gamma-ray doses and incremental neutron fluences upon the performance of self-biased 10B-coated high-purity epitaxial GaAs thermal neutron detectors

We report on progress with Schottky diode and p-i-n diode GaAs detectors for minimum ionising particles. The radiation hardness and potential speed of simple diodes is shown to be more than competitive with silicon detector. A discussion is given of the present understanding of the charge transport mechanism in the detectors since it influences their charge collection efficiency. Early results from microstrip detectors are also described.

GaAs solid state detectors for particle physics

The authors report on progress with Schottky diode and p-i-n diode GaAs detectors for minimum ionizing particles. The radiation hardness and potential speed of simple diodes are shown to be more than competitive with silicon detectors. A discussion is given of the present understanding of the charge transport mechanism in the detectors as it influences their charge collection efficiency. Early results from microstrip detectors which are relevant for high radiation regions of Large Hadron Collider (LHC) detectors near the beam pipe and in the forward region are also described. The authors have established the ability of GaAs Schottky diode detectors to tolerate radiation loads at the level expected in more than one year of running at a radial distance of only a few cm from the intersection point of the proposed LHC collider at nominal luminosity. The diode output signal of only a few nanoseconds is very satisfactory for the new colliders. >

P. G. Pelfer

Papers

GaAs solid state detectors for particle physics

GaAs solid state detectors for physics at the LHC