الفهرس 
General background and Literature reviewOnly 14 pages are availabe for public view
 |  | from | 146 |  |  |
| | | from | 146 | | |
Abstract
The present work was devoted to investigate structural, optical and
electrical transport properties of Zn doped GaP single crystals (GaP:Zn)
which were supplied from Sparta chemical industries (country) and they have wafer shape and p-type conductivity with concentration 1-2 x 10-18cm-3 at room temperature.
The structural properties of GaP:Zn single crystals were tested by using X-rays diffraction and indicated that these samples have cubic structure with a preferred orientation (200) plane and the lattice constant value was 5.447 Å
The optical properties of GaP:Zn single crystals were investigated in the spectral range of 200-2500 nm. It was found that the spectral distribution
of n R, and 1 reflected sharp structures due to the valence conduction band transitions ( , , ) 1 2 E E E andE g o having the energies 2.16, 2.7, 3.7 and 5.24 eV respectively. The investigated samples exhibited an indirect allowed optical transition associated with two phonons of energies 23.5 and 59 meV. The free carrier concentration was found to be 2.11 x 1018 cm-3. The oscillation energy, osc E , the dispersion energy, d E , the lattice dielectric constant l and
the optical dielectric constant at infinite frequency,, were calculated and
found to be the values 4.4 eV, 38 eV, 10.27 and 9.7 respectively.
The DC electrical conductivity was measured for GaP:Zn single crystals from room temperature (308 K) to 393 K and the DC activation energies were determined to be 1.07 and 0.22 eV for intrinsic and extrinsic conductions, respectively.
AC electrical conductivity of GaP:Zn single crystals was investigated and measured in the frequency range of 4-20 KHz and temperature range 308-393 K. Such measurements allowed us to determine the mechanism of charge carrier transport. The frequency dependence of () follows the Jonscher’s universal dynamic law with relation ()= (0) + As where is
the angular frequency of the applied AC field. The value of s is (0.75 ≤ s ≤
0.92) in the same range of temperature. The AC conduction mechanism has been described by the correlated barrier-hopping model (CBH).
Dielectric properties of GaP:Zn single crystals were measured and analyzed in the frequency range 4-20 kHz and temperature range 308-393K.
The values of static dielectric constant, s , high frequency limiting dielectric constant, and dielectric relaxation strength, , were determined from complex Cole-Cole plots at different temperatures.