Germanium-based Blocked Impurity Band Infrared Detector And Its Photoelectric Properties

The development of human science and technology is essentially the process of human exploration and understanding of the world.Infrared astronomy detectors are powerful tools for mankind to explore the outer space world,so its importance is self-evident.Blocked Impurity Band(BIB)detectors have become the mainstream detectors in the field of mid and far infrared astronomical detection due to its excellent performance,and have been widely deployed with various large-scale astronomical detection platforms,such as Cosmic Background Explorer(COBE),Spitzer Space Telescope and James Webb Space Telescope(JWST).However,despite the great success of BIB detectors,many of their working mechanisms at low temperatures are still confusing.In addition,the research on BIB detectors is still in its infancy in our country,which limits the development of infrared astronomy.Therefore,it is urgent to conduct in-depth and systematic research on BIB detectors.This thesis mainly focuses on the physical model,parameter optimization,device preparation,test method,photoconductive gain,interfacial barrier and structure improvement of BIB detectors.The research is carried out through a combination of theoretical analysis and experimentals.The main innovations of the research work are listed as follows:1.By improving the preparation process and optimizing the device parameters,we successfully developed the high performance Ge:B BIB detector.At 3.5 K and 30 mV,the spectral response covers a broad range from 15 to 200?m,with the peak response locates at 117.9?m.The blackbody responsivity is 1.47 A/W,and the detectivity is 2.97×10¹³ cm?Hz^1/2?W^-1.The peak responsivity at 117.9?m reaches 21.46 A/W,and the corresponding detectivity reaches 4.34×10¹⁴ cm?Hz^1/2?W^-1.Overall,the performance has reached the international advanced level.By studying the dark current,we found that as long as the breakdown characteristic exists,the dark current will maintain at a small magnitude before breakdown,and the detection performance will maintain at a high level.2.In order to circumvent the shortcomings of the high temperature blackbody test system,a low temperature blackbody test system was specially designed and set up. The low temperature blackbody test system has three advantages:(1)It can avoid the influence of background radiation.(2)The radiation characteristics of the low temperature blackbody is similar to that of the detection target of BIB detector.(3) It avoids the impact of mechanical vibration,so that a closed-loop cryostat can be used,thereby reducing the experiment cost.Using this test system,we have studied the influence of the electric field on the photoconductive gain of the Ge:B BIB detector,and proposed the gain operating mode.According to the gain mechanism of photocurrent and the breakdown mechanism of dark current,we give a reasonable explanation for the gain operating mode.In the gain operation region, the photoconductive gain of the device is several magnitudes larger than that in the other region,which is conducive to the detection of weak signals.3.By studying the interfacial barriers in BIB detectors,we found that the barrier height can be adjusted by changing the doping concentration,and therefore,we have fabricated several Ge:B BIB detectors with different barrier heights and proposed the interfacial barrier blocking mechanism.For the interfacial barriers between the ontact region and its nearby regions,they can block the injection of carriers in the contact region to the nearby regions,thereby reducing the dark current.In addition, carriers in the contact region can also cross the interfacial barriers by absorbing infrared radiatio,contributing to the extension of the spectral response range.For the interfacial barrier between the absorbing region and the blocking region,it can block the transporation of carriers close to the edge of the valence band.By increasing the operating voltage,the probability transporting through the interfacial barrier can be increased,and therefore,the relative response intensity in the long-wavelength region can be increased.4.In order to break through the limitation of the width of the depletion region in conventional BIB detectors,we designed and prepared the multi-junction blocked impurity band(MBIB)detector.MBIB detector consists of multiple absorbing regions and multiple blocking regions,so it has multiple interfaces and multiple depletion regions.In addition,we found that MBIB detector can avoid the unidirectional operation characteristic of BIB detector,and can always work on concentrational operating mode with high performance.Compared with BIB detectors,the performance of dual-junction MBIB detector has increased by 34.7%,while the performance of five-junction and ten-junction MBIB detectors have even increased by 20 times.According to the preliminary experimental results,MBIB detector has great potential to replace BIB detector,becoming the mainstream detector in the field of medium and far infrared astronomical onservation.