Dual-band Infrared Detector Using Type-Ⅱ Superlattice Based On GaSb Substrate

Infrared detector can be widely used in satellite detection, infrared guidance,infrared early warning and infrared thermograph and so on. Especially the dual-banddetector has more excellent performance than single channel devices. In recent years,InAs/GaSb type-II superlattices (T2SL) photodetectors have been attracted owing totheir unique broken-gap band-structures and potential applications. The T2SLsuppress Auger recombination and dark current, improve work temperature and adjustwavelength from3μm to30μm. Then, it has good prospects in the field of MWIR,LWIR and multi-band.In this paper, we are researching on a InAs/GaSb type-Ⅱsuperlattice dual-band(MWIR/MWIR) infrared detectors, the two cut-off wavelength are4.2μm and5.0μm,the structure is n-p-n design, two p-i-n structure place back-to-back and theP-electrode is the communal electrode. Firstly, the device structure was designedaccording to principle of detection after analyzing the T2SL properties. Secondly, ourwork emphasis focused on the optimized of lithography mask layout andmanufacturing process of the dual-band detectors. We took device area optimization,electrodes optimization, layout mark optimization, multifunction optimization andmultipurpose optimization in layout design. We also took optimized in lithography,ICP etching, passivation and metal stripping etc. some key process in manufacture.The last, we measured I-V characteristics, blackbody detection rate and spectralresponse.The main work of this paper includes:1. The paper summarily introduces the development of InAs/GaSb SL detectors ininternal and abroad, and application prospects. Analyzing the structure of energy bandand working principle in the superlattice detector of InAs/GaSb. This papersummarizes the advantages and disadvantages of InAs/GaSb detector by comparingwith the multi-quantum well infrared photo detector (QWIP) and mercury cadmiumtelluride (HgCdTe) detector.2. This papper took a number optimization in the design of lithography masklayout, including area optimization, electrodes optimization, layout mark optimization, multi-function (passivation, anti-reflection and protection layer) optimization,multi-purpose (transparent and medium, single band and dual band) optimization ect.3. The lithography process is optimized according to confirm suitable thicknessof photoresist and rotate speed of rubber coating. Through many times trial, the bestexposure, development and baking time have been confirmed. We are using two timesexposure if the thick photoresist is too thick.4. In the experiments, we used SiCl4/Ar with Cl2/Ar two etching gas source inICP (Inductively Coupled Plasma) process, comparing the two gas effect for etchingrate and uniformity. Finally, the optimum etching gas ratio is Cl2:Ar=3sccm:9sccm.5. The passivation material and thickness are optimized. In the experiments, wecompared SiO2and Si3N4two kinds of material in passivation process, and foundSiO2was more excellent for manufacturing process and electrical properties. Besides,the thickness of SiO2was thicker, and the result of passivation is superior.6. The manufacture of electrode was optimized. The thicker of turnoverphotoresist was benefical to get the complete electrode pattern in the metal stripping.The best condition of rapid thermal annealing has been confirmed by trial and error.7. We measured I-V characteristics, blackbody detection rate and spectralresponse of the dual-band device, and analyzed the test results.