Analyses On Dark Current Mechanism Of Long-wavelength HgCdTe Focal Plane Array Infrared Photodetectors

Mercury cadmium telluride(MCT)has significant application prospect in infrared detection field for its tuable band gap nenrgy,better electron monility,high quantum efficiency.The band gap of HgCdTe can change from-0.3eV to 1.6eV with the variation of Cd composition,HgCd Te photodiodes own detective ability in short-wavelength infrared band,mid-wavelength infrared band and long-wavelength infrared band.Especially in the long-wavelength infrared band,they still have high responsibility,meanwhile,long-wavelength infrared detection is main objective of the third generation high performance focal plane array frabrication.However,the band gap of longwavelength HgCdTe diode is so narrow that high performance detector has higher requirements on material growth,device design and frabrication.The dark current is the key performance-limiting factor of the photodetectors,so the study of dark current mechanism is a significant tool to archieve high performance long-wavelength detectors.Based on the experiment data,coupling with refine numerical and analysis model,this paper has researched the dark current component and action mechanism.The dark current component of detectors with different structure and doping method were archieved,the key parameters were extracted,these works gave guidance for experiment design and the refine numerical and analysis model could predict the perforamnce of the detectors.The detail research contents and results are shown as follows:1.Analysis on 9?m double layer heterojunction long-wavelength HgCd Te photodetector was carried out.By analysical model,two different n-type doping concentration devices were researched,it found that trap-assisted tunneling current is the domain current when the diodes are under large reverse bias at 80 K,the trap-assisted tunneling current is far larger than band to band tunneling current;with temperature increasing,the minority carrier lifetimes become lower and equivalent defect level moves to valence band;comparing the devices with different doping concentration,it found the high doping concentration induces high trap concentration,so low n-type doping technology needs to explored.2.Analysis on 15?m DLHJ very-long-wavelength HgCdTe photodetector was carried out.It found that the performance of very-long-wavelength HgCd Te photodetector is more sensitive to the defects and device fabrication.When the devices are under large reverse bias,tunneling current is the major dark current component,and the generation-recombination current domains dark current when the devices are under little reverse bias however the bad performance device is trap-assisted tunneling current.With the temperature raising,the minority carrier lifetimes become lower just same as other detectors.The Cd component buffer layer is simulated and analysied,it can influence the detectivity and response.The traps,defects and Cd component buffer layer always cause the non-uniform of FPAs.3.The 12.5?m n-i-p Au and Hg-vacancy hybird doping p-type epitaxy HgCd Te infrared detectors were simulated and analysied.Firstly,the refine simulation analysis model is raised,the simulated dark current is much closer to the experiment datas comparing to the precious model.The dark current component were simulated and it found that the larger p-type doping concentration,the larger band to band tunneling current is,and the distribution of electric field shows the reasons for this phenomenon.The simulated minority carrier lifetimes show close related to the product factor which proves the accuracy of this model.At last,the proposed theory Au interaction with Hgvacancy clearly explans the minority carrier lifetime has a trend of rise first then fall with the p-typt doping concentration increasing.