Study On The Effect Of Annealing On The Resistivity Of CdZnTe

CdZnTe is one of the most important II-VI compound semiconductor materials.Because of the exceptional photoelectric property of CdZnTe, recent years we witnessthe expansion of CdZnTe room-temperature semiconductor radiation detectortechnology into many applications such as medical imaging, industrial processmonitoring, national security and treaty verification, environmental safety andremediation, and basic science and so on. So, it has broad application prospects andgreat market value. The CdZnTe material used for radiation detector should have highresistivity (ρ>108Ω cm). However, most CdZnTe material has relatively low resistivity,thus it is unable to meet the requirements of the fabrication of detector. In this way, itis important for us to systematically investigate the method for improving itsresistivity. In this paper, we mainly studied the effects of annealing on CdZnTe crystalabout its resistivity. By modeling the diffusion of In atoms in CdZnTe crystal andcombining the change of resistivity before and after annealing, we systematicallystudied the relationship between annealing processes, diffusion coefficient and theresistivity of CdZnTe.In this experiment, we mainly studied the effects of annealing on CdZnTeresistivity in In atmosphere conditions. By combining semiconductor diffusion theoryand the diffusion mechanism of In atoms in CdZnTe crystal, we successfully build thediffusion theory of In atoms in CdZnTe crystal. It is found out that the reason for thechanges of electrical properties of CdZnTe crystal is the diffusion and compensatoryprocess of In atoms, and annealing temperature and time. We successfully obtainedthe integral expressions of resistivity and diffusion coefficient of In atoms in CdZnTecrystal. Finally, we obtained the diffusion coefficients of In atoms in CdZnTe crystalin the different temperatures and the function expression of diffusion coefficient in thedifferent temperatures ranging from1073K~973K. Additionally, we also obtained thefrequency factor D0(2.15cm2/s) and activation energy of diffusion E0(1.9eV), etc. Thedata we got has significant value for the intensive study of annealing of CdZnTe. In this paper, we also proposed a new method for accurately measuring theresistivity of high resistivity CdZnTe crystal. As is well known, it is difficult tomeasure the resistivity of CdZnTe crystal accurately. We successfully measured theresistivity of high resistivity CdZnTe crystal with accuracy, using Cu film electrodeand Keithley Model6430stored program control meter.The resistivity of CdZnTe crystal is greatly improved after being annealed in theIn atmosphere conditions. This study greatly improves the resistivity of CdZnTecrystal with4orders of magnitude, which has crucial importance in the fabrication ofhigh resistivity detector material.Based on the semi-infinite diffusion model, if the concentration distribution ofimpurity is available, we can obtain the diffusion coefficient of the impurity inCdZnTe crystal using this model. Moreover, this study also authenticated a newmethod to study the diffusion coefficient of electrically active impurity. Specifically,some semiconductor crystal is annealed in the electrically active impurity atmosphereconditions. Based on the theory in this paper, we can obtain the diffusion coefficientof the impurity in this semiconductor crystal if we know the changes of resistivitybefore and after annealing and the surface concentration of the impurities.