Research and Development of Advanced GaAs-Based Technology for the New Type Radiation Detectors
Tech Area / Field
- FIR-OTH/Other/Fission Reactors
- INS-DET/Detection Devices/Instrumentation
3 Approved without Funding
Joint Institute of Nuclear Research, Russia, Moscow reg., Dubna
- Tbilisi State University, Georgia, Tbilisi
- High Energy Accelerator Research Organization, Japan, Tsukuba\nShinshu University / Japanese Linear Collider Calorimeter Group, Japan, Nagano\nCANDU Owners Group, Canada, ON, Toronto
Project summaryFor many years gallium arsenide (GaAs) and related compounds along with silicon (Si) have occupied a firm position as a material for micro-and optoelectronic devices.
It is well known that for detection of different kind of radiation GaAs has significant advantages over Si, namely:
- shorter actuation time;
- higher thermostability;
- higher radiation resistance.
These three characteristics are related to such distinguishing features of GaAs as high carrier mobility (determines high-speed performance) and large band gap (determines thermostability and radiation resistance).
These two parameters in GaAs against Si at 300K are:
Carrier mobility [cm2/(V.s)]
Band gap (eV)
It is well known that high-speed performance of III-V devices and IC’s is on the average higher by an order of magnitude than in silicon devices.
If the average operating temperature of silicon devices is 150oC, for GaAs this value is twice as high.
And finally, the value of 108 rad is taken as a boundary dose for normal operation of most GaAs devices.
Today GaAs is believed to be the most promising material for fabrication of radiation detectors used in diagnostic medicine, structural biology, space investigations, high-energy physics, dosimetry, non-destruction control in industry, etc.
The objective of the present project is a creation of a calorimeter module prototype for high energy physics using a Photomultiplier (PM) as a GaAs pixel matrix (monolithic version) produced on the base of the development of advanced GaAs-based technology for different type radiation detectors proposed in the project.
The problems of PM creation based on semiconductors were more or less successfully solved using a silicon technology on p-n junction where PM could operate as a monolithic unit of multi-purpose application.
However, due to the above mentioned peculiarities of GaAs a photodetector based on this semiconductor material will be superior in a number of properties to its silicon analog. Detection of light signals should also be performed as a result of appearance of a self-quenching Geiger discharge in each pixel when light quanta get into the pixel active region of the device.
For future high energy physics experiments where higher collision energy and higher luminosity are expected it is extremely important for detector calorimeter to have very good energy resolution (~30%vE) to identify W- and Z-jets in events. In conjunction with corresponding software – Particle Flow Algorithm (PFA) – such jet energy resolution can be achieved. That is why the calorimeter parameters must be optimized from PFA requirements point a view. Among others fine segmentation in 3-dimentions is essential. A sampling calorimeter with small tiles/strips of plastic scintillator as active detector can be chosen as promising candidate. For such a scintillator-based calorimeter the Photomultiplier converting the light incident thereon to an electric signal plays the key role. The proposed GaAs PM should have:
- high sensitivity to visible light (photon absorption coefficient in GaAs within photon energies from 1,2 to 3eV is higher by an order of magnitude than in Si,
- high gain without any amplifier (no less than 5 ·106 in GaAs against 106 in Si),
- low operating voltage (no more that 40V for GaAs against 50V in Si),
- high photon counting capability (no worse than in Si),
- low noise level (noise-factor 1,1 – 1,2),
- fast signal and short recovery time (60-70ps in GaAs against 100ps in Si),
- low amplification factor sensitivity to magnetic field,
- operating temperature range up to 250oC,
- direct bonding to the tile/strip and attached to WLS (Wave Length Shifter) fiber at the same time not making dead regions in the calorimeter
- compact size.
Investigations will result not only in development of an advanced GaAs technology for different radiation detectors, but in creation of practically a new semiconductor device to be applied first of all in thin plastic scintillators with an inserted WLS fiber. The device should be compact enough to be placed into special grooves in the scintillator tile/strip.
The development is to be completed by fabrication and test of about 100 devices mounted on chip carriers with a passivating coating.
In the framework of the present project main ISTC goals and objectives should be met: redirecting the specialists’ activity from military to peaceful purposes and further integration of scientists into the international scientific community; restoring applied research to get results that are needed in industry.
The scope of activity is defined by the goals and the expected final results.
To realize the above-mentioned goals the project is pided into four main tasks: theoretical stage, development and fabrication of test chips, fabrication of demonstrators and elaboration of design and technological documentation. In the framework of main tasks a number of subtasks is to be executed in parallel, in particular, development of design and technological processes.
The scope of activity, as a whole, includes development of a functional design and then a final version of the device, material investigation, elaboration of a process flow and methods for amplifier parameter testing and as a result – development of an integrated Photomultiplier (PM) module.
As a final step some electromagnetic (EM) calorimeter prototype module will be designed and constructed with GaAs-based PM`s and its properties will be experimentally investigated on the test beams of electrons, muons and pions. A well-documented advanced technology will also be developed.
The technical approach and methodology involve different aspects of project activity: scientific, technological, engineering and organizational.