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Professor,
Materials Science and Engineering,
Indian Institute of Technology-Kanpur ,
Work Phone: (512) 2597353,
Email: saboo[at]iitk.ac.in
Materials Science and Engineering,
Indian Institute of Technology-
Email: saboo[at]iitk.ac.in
Kaushik Nandi’s Thesis
Thesis Topic:
First principle calculations on point defects in GaAs
First principle calculations on point defects in GaAs
We have carried out ab initio total energy calculations using the density-functional theory to study the native defects in GaAs material. First principle pseudopotentials for Ga and As were generated according to the Bachlet-Hamann-Schlüter scheme using the computer code fhi98pp. These pseudopotentials were fully separable and norm conserving in nature. In order to ensure the accuracy of the results hard pseudopotentials were generated. The total energy calculation was performed with another code fhi96md. Lattice constants of Ga, As and GaAs were optimized on the basis of total energy minimization. All the calculations were done at 20 Ry cutoff and only the electron minimization scheme was employed using the second order damped Joannopoulos algorithm. The supercells for the calculations were constructed from four cells of Ga and As each and eight cells of GaAs. For exchange and correlation local density approximation (LDA) was employed. Heat of formation of GaAs was calculated for these optimized structures by subtracting the bulk energies of Ga and As from the bulk energy of GaAs. Though the individual energies of the materials concerned are close to those published in the literature, our results show that the heat of formation is 0.36 eV where as the experimental result is 0.74 eV. Various point defects were introduced in a GaAs crystal by physically removing the atoms. The formation energies for defects at different charge states have also been examined.