Research On Readout Circuit And Its Anti-radiation Property For Resistive Ga₂O₃ UV Detector

With the rapid development of UV detection technology in the military and civil areas, a variety of new UV detectors have been discovered. The readout circuit of resistive Ga₂O₃ UV detector must be designed according to its electrical characteristics because resistive Ga₂O₃ UV detector is a new kind of UV detectors. Meanwhile, with the wide applications of UV detector, more and more UV detectors have been used for space exploration, such as UV space-based early warning system. So the anti-radiation performance of the detection circuit has to be considered.A UV detection system was designed around resistive Ga₂O₃ UV detector, while a readout circuit for resistive Ga₂O₃ UV detector and its anti-radiation property has been studied carefully. The CTIA readout circuit configuration is selected according to the electrical characteristics of Ga₂O₃ ultraviolet detector, which includes an operational amplifier, integrating circuit, sample and hold circuit and a buffer circuit. The CTIA readout circuit was designed and circuit simulation results show that readout circuit can provide less than 1 mV offset voltage for the ultraviolet detector and photocurrent injection efficiency of the detector is greater than 99%. A 4 × 4 UV detector array and its digital control circuit were designed and output voltage fluctuation of the detector array is less than 1 m V. Then the layout and post simulation of the entire UV detector array was also accomplished. The post simulation results show that the detector array can function well and its linearity is more than 98%.In order to study the anti-radiation performance of the readout circuit, a radiation experiment was carried out on both conventional and enclosed-gate n-MOSFET. The experimental results show that enclosed-gate n-MOSFET owns good anti-radiation properties while sub-threshold slew rate and output resistance of conventional n-MOSFET have both been degraded in the total ionizing dose environment. Then n-MOSFET BSIM model parameters were extracted using the test data of n-MOSFET transistor which is irradiated at 100 krad, 300 krad and 500 krad. The circuit simulation results and test results were compared to verify the accuracy of the model parameters. Finally the simulation of the readout circuit was executed using the model parameters extracted from n-MOSFET to predict the performance of the readout circuit irradiated. The simulation results show the gain of the operational amplifier dropped 20 dB when the operational amplifier was irradiated at 500 krad. The reason caused gain of the operational amplifier to drop was analyzed and the operational amplifier was redesigned. The simulation results of the redesigned readout circuit show that the ultraviolet readout circuit can function well and its accuracy and linearity was not affected by irradiation.