Ring Porous, Ion Beam Etching Hgcdte Photodiodes And Mis Devices Research

The band gap energy ofⅡ—Ⅵcompound semiconductor Hg_1-xCd_xTe alloyranges from -0.3eV to 1.6eV, which covers three important infrared wavebands of1～3μm, 3～5μm, 8～14μm. The material is important in infrared imaging, pollutionmonitoring, industrial process control and so on. The HgCdTe loophole pn junctionformed by energy ion beam milling is a novel compound detector with advantages offast response, high sensitivity, high stability, low price, high intergraded density andso on.In this dissertation, theⅠ-Ⅴ, R_D-V characteristic of HgCdTe loophole photodiodeand the C-V characteristic of HgCdTe MIS device were calculated and analyzed. Thenthe interface chemical structure of MIS device was researched by XPS analysis. Thefollowing is the main work and results:1. A new simply, precise, intuitional method and formula for calculating and analysisⅠ-Ⅴcharacteristic of pn junction were deduced. We used the method to calculateand analyze theⅠ-Ⅴ, R_D-V characteristic of some HgCdTe loophole pn junctions.We obtained a lot of important parameters, such as surface leakage conductance,diode ideality factor n distributing with voltage, dI/dV-V curve, which are vital todiode characteristic. The study indicated that surface leakage current tunneling hasa very important effect on the reverseⅠ-Ⅴcharacteristic. The crystal defect ofHgCdTe material make diode ideality factor n, G-R current and trap-assistedtunneling current obviously increased.2. The HgCdTe loophole pn junction formed by energy ion beam milling is a linerjunction judged by its C-V curve. And the grade of impurity concentrationdistribution is known from 1/C³-V curve. We calculated some importantinformation by Poisson's equation, such as build-in electric field distribution,build-in potential distribution. Then we analyzed the cause and process of HgCdTeloophole pn junction formed by energy ion beam milling.3. The fabrication of HgCdTe MIS device, basic principle and steps(included measurehe interface state density with energy distribution for the passivation films inHgCdTe MIS device, through the low and high frequency capacitance combinedtechnology) to calculate and analyze the interface electrical characteristic throughC-V curve are introduced. The formules of impurity distribution in substrate arededuced by using the high frequence C-V characteristic of MIS device in depletion region. The study indicated, there are many useful results. For example,the fixed charge density of anodic sulfidization+ZnS passivation isabout 7.6×10¹⁰/cm²,the impurity concentration distribution in substrate, theinterface trap density with energy distribution and low slow interface trap density.All of the indexes are better than anodic oxide film, close to CdTe+ZnS doubleinsulator films. It is a mature method for HgCdTe FPA surface passivation. It hasalready reach the various demands of surface passivation for PV HgCdTe focalplane arrays(FPAs) devices.4. The structure of anodic sulfide+ZnS passivation films was analyzed by XPS. Theresults showed that the main of anodic sulfide film is CdS. In the processes ofsurface treatment, because the relative rates of Br₂-CH₃OH and HgCdTe elementsare different, the surface left more Te, less Hg, Cd, generate TeO₂ and the surfacewas rough distinctly, which cause interface trap density increase, passive film lieto including passitive charge and surface leakage current increase.