Research On Performance Characterization Methods Of Quantum Dot Infrared Photodctectors

With the expanding and deepending of the detecting application, there are moreand more demands for the high performance and high quality detectors. Due to itsspecial quantum dot nano-structure, quantum dot infrared photodetectors, which emergein recent year, show more efficiency properties such as a low dark current, a high gain,and thus attract a wide attention. Since traditional performance methods don’t considerthe influence of these factors, the performance characterization methods of quamtumdot infrared photodetectors are studied from four aspects in this paper, which willprovide us with reliable theoretical support for the detector optimization. Specifically,these works are as follows.1. Electron transports in quantum dot infrared photodetectors are analysised, and adark current model is proposed. In the model，the microscale and nanoscale electrontransports are considered, the dark current is forecasted and estimated by counting thecarriers in the barriers. This dark current model is improved with the consideration ofthe relationship between the drift velocity of electrons and the bias voltage of thephotodetector. As a result, the calculation of the dark current is more accurate than thatof the previous dark current.2. Based on the improved dark current model, the noise model of quantum dotinfrared photodetectors is proposed with the calculation method of photoconductivegain. Firstly，after the time from the extend state to gound state of carriers in thediffusion limited system is analysed, the photoconductive gain model is obtained withthe structure characteristics of quantum dot infrared photodetector. Sencodly, the noisefeatures of the photodetector are analysed, and it is pointed out that the noise come fromthe generation-recombination procession of carriers. in the end, the noise model of thequantum dot infrared photodetector is built with the consideration of the gain model.The calculated results show that the model makes the calculation of the noise moreconsistent with the work mechanism of the photodetector.3. Based on the dark current model including two electron transports, theperformance models of photodetectors are built from the two aspects which are theemission of and the continuous potential distribution of electrons. The performancemodel on the basis of electron emission supposes that there are two electron emissions:thermal emission and field-assisted tunneling emission. The number of carriers in aquantum dot is obtained by estimating the carriers rates of the thermal emission andfield–assisted tunneling emission, and the current balance relaition under the dark condition is obtained, thus the models for the photocurrent, responsivity and detectivityof the photodetectors is bulit. The performance model on the basis of the electronscontinuous potential distribution supposes that the potential distribution satisfied thepoisson distribution, by sloveling the Poisson equation and considering the relationbetween the current through the punctures in the planar potential barriers and potentialdistribution, the performance models of photodetectors such as photocurrent，detectivityare built together with the previous dark current model. Finally，the comparisionbetween two performance models is made，and the differences between them areillustrated.4. The properties of quantum dot infrared photodetectors under different incidentmodels are analyzed. Firstly, J.Phllips model of the photodetector under the normalincidence is built, and then the normal incidence dark current and detectivity are studied.Secondly, the properties of the quantum dot infrared photodetector under the normalnormal incidence and oblique incidence model are compared. In the end, the advantagesin properties of quantum dot infrared photodetectors under different incidence modelsare presented by the comparision between quantum well infrared photodetectors andquantum dot infrared photodetectors.