Contributions of point defects, chemical disorder, and thermal vibrations to electronic properties of Cd1−xZnxTe alloys

Abstract

We present a first principles study based on density functional theory of thermodynamic and electronic properties of the most important intrinsic defects in the semiconductor alloy Cd1−xZnxTe with x < 0.13. The alloy is represented by a set of supercells with disorder on the Cd/Zn sublattice. Defect formation energies as well as electronic and optical transition levels are analyzed as a function of composition. We show that defect formation energies increase with Zn content with the exception of the neutral Te vacancy. This behavior is qualitatively similar to but quantitatively rather different from the effect of volumetric strain on defect properties in pure CdTe. Finally, the relative carrier scattering strengths of point defects, alloy disorder, and phonons are obtained. It is demonstrated that for realistic defect concentrations carrier mobilities are limited by phonon scattering for temperature above approximately 150 K.

First-principles study of atomic and electronic structures of60∘perfect and30∘/90∘partial glide dislocations in CdTe

“…30 On the other hand, the remaining Cd B3 adopts a nearly planar sp 2 configuration with its three Te neighbors; such a planar CdTe 3 configuration is reminiscent of the atoms surrounding a Te vacancy in CdTe. 6,31,32 Our calculation predicts that the QP structure is 0.58 eV/nm lower in energy compared to the SP structure. • glide dislocation.…”

Characterization of point defects in CdTe by positron annihilation spectroscopy

“…27,30 Recent firstprinciples calculations of point defects in CdTe have provided further insight on local structure and stability. [1][2][3][4][5]31 Possible relaxed geometries of the two stable charge states, À1 and À2, of the Cd vacancy, 1,3 and for the À1 charge state of Cl-donor A-center, V Cd with a Cl Te nearest neighbor, 2 have been reported. The other point defect considered of particular importance in these materials is the Te antisite; this has also been studied and relaxed structures for the three charge states, Te þ2…”

“…Despite many decades of experimental studies, using a range of different techniques, routine detection and unambiguous identification of point defects in CdTe and related materials remains a challenge. However, increasingly accurate density functional theory (DFT) calculations are providing valuable insight on the nature and behavior of point defects in CdTe 1-4 and Cd 1Àx Zn x Te, 5,6 and these are, in turn, aiding the interpretation of experiments. The experimental methods that are capable of detecting point defects with a sensitivity better than 10 16 cm À3 , and which provide information on local structure, include the positron annihilation spectroscopy techniques.…”

Simulating Interface Growth and Defect Generation in CZT – Simulation State of the Art and Known Gaps

“…There have been many studies of defect and absorption energetics of CdTe and CZT using DFT [230,[327][328][329][330][331][332][333][334][335][336][337][338][339][340][341][342][343][344]. Even though DFT has been very successful in predicting structures, properties and reactivities for a wide variety of molecular and solid-state systems, the accuracy of the defect energies from DFT has not been rigorously validated from experiment or higher levels of ab initio theory.…”

“…This approach has been used by Aberg et al in their recent DFT study of defects in CZT alloys [334]. A drawback of this method is that a dielectric constant has to be estimated [353], although for many materials this constant is known.…”