Abstract:
ZnSe is a hard and intrinsic semiconductor material with a naturally occurring
hexagonal or cubic structure. It is potential material for optical devices in the visible
and infrared regions due to its large direct band gap of 2.7 eV and strong exciton
binding energy. The band gap of ZnSe can be modified to an optimal value in order to
properly implement this semiconductor's properties for a specific application. The
present research work focuses to investigate the structural and electronic properties as
well as absorption coefficient of Mn-doped ZnSe materials in cubic and hexagonal
phases using CASTEP numerical coding. Optimized lattice constants are used to
construct supercell 2×2×2 for cubic and 1×2×2 for hexagonal supercells to explore the
effect of Mn-dopant on structural and optical behavior of ZnSe. The GGA-PBE
functional with ultra-soft pseudo-potential for cubic and OTFG-ultrasoft pseudopotential for hexagonal configurations is used for non-spin-polarized calculations.
Direct band gap of 0.372eV from cubic and 0.912eV from hexagonal are observed for
pure ZnSe supercell, whereas the Fermi level resides between the conduction band
and valence band. The energy gap 0.109eV, 0.183eV, and 0.129eV for cubic and
energy gap 0.349eV, 0.078eV, 0.087eV for hexagonal structure are observed for one,
two and three atoms Mn doped ZnSe which is decreased due to presence of Mn
impurity atoms. The absorption spectral peak at 2.6×105
cm-1
for pure ZnSe and
1.28×105
cm-1
, 2×105
cm-1
and 1.96×105 cm-1
are observed on introducing Mn as
dopant in ZnSn. Reflectivity, dielectric function, refractive index, conductivity and
loss function are decreased with increase in the number of Mn-dopant atoms in ZnSe
structure for both cubic and hexagonal phase. The calculated results showed interband
absorption due to presence of Mn impurities.
