Optical absorption and photoconductivity in gamma-irradiated zinc selenide crystals
D. B. El'murotova,
E. M. Ibragimova Institute of Nuclear Physics, Academy of Sciences of Uzbekistan, Tashkent
Abstract:
The possibility of radiation-induced enhancement of photoconductivity
$(\sigma_{ph})$ in crystalline zinc selenide (ZnSe) has been studied. The electron concentration in the initial ZnSe:O crystal was
$N_{E_g}$ = 1.26
$\times$ 10
$^{16}$ cm
$^{-3}$ as determined from the optical density of the sample at
$E_g$ = 2.58 eV. The irradiation of the ZnSe:O crystal by gamma-photons from
$^{60}$Co source to a dose of 10
$^6$ Gy leads to the creation of five new energy levels (
$\Gamma_{6v}$ – 5.76 eV;
$L_{1.3v}$ – 4.85 eV; Zn
$_i$ – 3.34 eV; O
$_{\mathrm{Se}}$ – 3.13 eV;
$X$ – 2.72 eV), a decrease in the electron concentration to
$N_{E_g}$ = 0.63
$\times$ 10
$^{16}$ cm
$^{-3}$, and a twofold increase in
$\sigma_{ph}$. The doping with Te to 0.2 wt% also creates the
$L_{1,3v}$ level and increases
$N_{E_g}$ to
$\cdot$ 10
$^{16}$ cm
$^{-3}$ and
$\sigma_{ph}$ to 2.01
$\times$ 10
$^{-10}$ $\Omega^{-1}$. The irradiation of Te-doped crystals leads to the creation of an additional resonant level (Zni, 3.34 eV) and a two-fold increase in
$\sigma_{ph}$. An increase in the content of Te to 0.5 wt% results in a shift of the Zn
$_i$ level to 3.39 eV and a growth in the conductivity to
$\sigma_{ph}$ = 7.6
$\times$ 10
$^{-9}$ $\Omega^{-1}$. However, the gamma-irradiation of these crystals leads to decomposition of this center and to a decrease in the photoconductivity.
Received: 25.12.2009
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