Defects and positron states in Hg1-xCdxTe semiconductors

Abstract
Single crystals of Hg1-xCdxTe (x=0.35, 0.27 and 0.20) were studied by positron annihilation in a temperature range from -150 to 500 degrees C. It was found that, when samples were heated from 20 to 500 degrees C, the positron mean lifetime tau and Doppler broadening lineshape parameter S always show a 'V'-type behaviour with a minimum at around 250 degrees C. The authors attributed this behaviour to the annealing and creation of Hg vacancies. The formation enthalpy of VHg2- was estimated to be 0.71 eV. The values of the positron lifetimes in the bulk state and in the VHg2- trapped state were obtained as 282 ps and 310 ps, respectively. The specific positron-trapping rate mu of VHg2- was estimated to be (5+or-1)*1014 s-1.

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