Dark Currnt And Noise Characteristics Investigation In Quantum Dot Infrared Photodetectors

High performance detectors are the goal that people strive to achieve in the field ofthe infrared detecting technology. Owing to the excellent characteristics of the quantumdot infrared photodetectors (QDIPs), such as lower dark currents, higherphotoconductive gain, increased extraction efficiency, higher detectivity, and increasedoperating temperatures, they have attracted more and more attention from theresearchers in recent years. In this paper, the dark current and noise characteristics ofthe QDIP are mainly investigated, which will provide the dependable theoretical andtechnical basis in the optimization of the device design and the pursuit of higherperformance of QDIP. The specific work carried out is as follows:(1) The dark current models of QDIP based on potential energy and activationenergy are analyzed, respectively. Based on the exact experimental data, an activationenergy dark current model of the QDIP including the common influence of themicroscale and the nanoscale electron transport to the activation energy is furtherverified at different temperatures, moreover, with account taken of the dependence ofthe drift velocity of electrons on the applied electrical field. The main concern is toanalyze the influence of QDIP parameters on the dark current characteristics, such asthe applied electrical field, temperature, two electrons transport (microscale andnanoscale), and detector material performance parameters (mobility of electrons,effective mass of electrons, and saturation velocity of electrons), respectively, and thereasons for the influence of each performance parameter on the dark current areinvestigated in detail.(2) Based on the analysis on the mechanism of noise in QDIP, the functionrelationship between the noise and the dark current is obtained, and the two noise gainand noise models of QDIP are respectively derived. A noise model of QDIP within therange of0-20KV/cm including the common influence of the microscale and thenanoscale electron transport to the activation energy is further verified at differenttemperatures based on the exact experimental data, moreover, with the consideration ofthe influence the applied electrical field on the drift velocity of electrons. The mainconcern is to analyze the influence of QDIP parameters on the noise in low voltage,such as the applied electrical field, temperature, two electrons transport (microscale andnanoscale), detector material performance parameters (mobility of electrons, effectivemass of electrons, and saturation velocity of electrons), and detector structural performance parameters (detector area, number of quantum dot (QD) layers, spacingbetween QD layers, lateral size of QD, height of QD, density of QD, and capture rate ofelectrons), respectively, meanwhile, the reasons for the influence of main performanceparameters on the noise in low voltage are investigated in detail.(3) Anoise physical model of QDIP within the range of20-45KV/cm including thecommon influence of the microscale and the nanoscale electron transport is furtherverified at different temperatures based on the experimental data, moreover, with theconsideration of the dependence of the drift velocity of electrons on the appliedelectrical field. The main concern is to analyze and discuss the dark current and thenoise gain characteristics, and the influence and reasons of QDIP parameters on thenoise in high voltage, such as the applied electrical field, temperature, two electronstransport (microscale and nanoscale), detector material performance parameters(mobility of electrons, effective mass of electrons, and saturation velocity of electrons),and detector structural performance parameters (detector area, length of the activeregion of the device, density of QD, effective radius of QD, and capture rate ofelectrons), respectively.(4) The noise characteristics of quantum dot infrared photodetector focal planearray (QDIP PRA) are investigated. The two models of noise equivalent temperaturedifference (NE T) of QDIP focal plane array (PRA) are established, and thetwo NE T are calculated in quantitative methods to the typical QDIP performanceparameters, respectively. The validity and correctness of NE T of QDIP PRA isverified by comparing the results between the calculation and the experimental data.The NE T of HgCdTe and the quantum well infrared photodetectors focal plane array(QWIP PRA) are analyzed respectively, and the results show that the QDIP PRAhas thebest NE T by the comparison among the threeNE T of HgCdTe, QWIP, and QDIPPRA. The signal and noise ratio (SNR) and the current injection efficiency of QDIPPRAare analyzed and discussed.