STRUCTURAL ELECTRONIC OPTICAL AND MAGNETIC PROPERTIES OF METALS DOPED III-V SEMICONDUCTORS

Abstract

In this thesis, we present theoretical studies of the structural, optoelectronic and magnetic properties of metals doped III-V semiconductors in the zinc blende phase. For the calculation of the physical properties of the com- pounds, we used the full potential linearized augmented plane waves (FP- LAPW) method within the density functional theory. In the Al1−x Gax N and Al1−x Inx N crystals, Al is replaced by Ga and In respectively in the step of 0.25 from 0 to 1. In In1−x Bx N, In is replaced by B for the entire range. We calculate the variation in the bandgap with the variation in the doping concentration. Frequency dependent optical pa- rameters such as complex dielectric function, refractive index, reflectivity, absorption coefficient, and optical conductivity of these materials are also calculated and are found to be concentration dependent. It is further no- ticed from the optical spectra that the refractive index drops below 1 for higher energy photons. In this energy range the group velocity of photon is larger than the vacuum velocity of light. This astonishing result shows that at higher energies the optical properties of these materials shift from linear to non-linear. This comprehensive theoretical study of the optoelectronic properties of these materials predicts that they can be effectively used in the optical devices working in the major parts of the spectrum. The magnetic nature, half-metallicity and robustness of half metallicity of transition metals doped III-V semiconductors in the zinc blende crystal structure are investigated. The calculated ground state spin polarized band structures and density of states of Al0.75 Cr0.25 N, Ga0.75 Cr0.25 N, Al0.75 Co0.25 N and Al0.75 Ni0.25 N reveal that these compounds are semiconductor for spin up state and conductor for spin down state. For the majority spin-channels the electronic cloud of the N-2p states overlaps with the TM-3d and 2s states and causes spd-hybridization, which is the origin of half metallicity in these compounds. The calculated spin-polarized band structure of In0.75 Cr0.25 N shows that it is conductor for both spin channels. The electronic structure and magnetic properties of Ga1−x Mnx P and Ga1−x Mnx As (x=0.125) are calculated and the feasibility of the growth of these compounds on different substrates on the basis of the variation in the lattice constants is discussed. The results show that, both the compounds hold their half-metallic nature (conductor for spin-up state and semiconduc- tor for spin-down state) with their lattice compressions up to certain critical lattice constants.