| Ternary compound semiconductor AlGaN is a kind of wide-gap and direct-gap semiconductor. It can change its bandgap from 3.4eV to 6.2eV continuously by changing the Al composition x,and the corresponding response cutoff wavelength is from 200 nm to 365 nm continuously, which covers the solar-blind ultraviolet waveband. So the solar blind ultraviolet detectors made by AlGaN material have attracted deep research and been widly used.In general, the back illuminated solar-blind ultraviolet detectors are fabricated on the multilayer AlGaN grown on sapphire(Al2O3) and the main structure is a p-i-n junction. To read out the response signals from focal plane detectors, the usual method is making a read-out circuit with silicon, then link the read-out circuit and AlGaN detectors together. But linking process will form stray capacitors of read-out circuit and addition capacitors of In column interconnect. These capacitors will lossen the current signals. If amplifying devices or a charge storage devices can be integrated on the detectors and amplify the response current signals or transfer them to the form of voltage, the output signals will be greatly enhanced and the influence of the stay capacitors will be reduced. This article introduces the numerical simulation of p-i-n solar blind ultraviolet detectors and the MESFET devices which have the feature of amplification. Then explored the fabricate process of devices and fabricated the solar blind UV detectors with an amplifier under the guide of theory data. At last, we did tests and analysis of the devices.Firstly, we analyzed and summarized the physical models of semiconductor photoelectronic detectors. Then used them to the calculation of p-i-n structured solarblind UV detectors and got the spectral response and I-V characters. We matched the simulation curve of spectral response to the testing data, and fixed the SRH recombination lifetime of carriers, and found that the SRH recombination lifetime is about 10-11 s. Using the fixed SRH recombination lifetime, we got a simulated spectral response result similar to the testing data. We also discussed the research we didi into the influence upon response spectral caused by SRH recombination lifetime and we got a series of results. The results shows that, when the SRH recombination lifetime is near 10-10 s, the ratio of responsivity in response waveband to the response signal before the response waveband is the largest. Then we did I-V simulation to the MESFET devices fabricated on p-GaN and got a conclusion that the MESFET can amplify signals.Secondly, we fabricated a kind of solar-blind integrated devices with multi-layer structure. The detector part has a structure of p-i-n and the response of it is 250nm~285nm. The signal amplifier and transverter are MESFET and MIS. Then we designed the processing sequence and we fabricated the p-i-n solar-blind UV detectors, MIS, MESFET, p-i-n+MESFET, and p-i-n+MIS on the same material.At last, we tested the fabricated devices and compared the testing results with the simulation ones. We made the C-f and C-V test of MIS capacitors that the dielectric layer thickness is 50 nm and 150 nm. The test results show that, the MIS with a 50 nm dielectric layer have a slight current leakage and the MIS with a 150μm dielectric layer performs better, it shows a good character of capacitor. Then we made I-V test to MESFET devices and found that, the gate voltage is lower, the conductivity between drain and source is better and the MESFET can act as an amplifier. We tested these two kinds of detectors with pre-amplifiers, and made comparation with the detectors without pre-amplifier. The results showed that the MESFET-integrated detectors can amplify the signals and the detectors integrated with a MIS can transform the output current into voltage. |
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