Electronic properties of semiconductors
Specific features of the temperature dependence of the conduction electron concentration in the narrow-gap and zero-gap states of Cd$_x$Hg$_{1-x}$Te
S. A. Aliev,
E. I. Zulfigarov,
R. I. Selim-zade Institute of Physics Azerbaijan Academy of Sciences
Abstract:
Results of studies of the conductivity
$\sigma$ and the Hall coefficient
$R$ in the Cd
$_x$Hg
$_{1-x}$Te crystals with
$x$ = 0.1, 0.12, 0.14, and 0.15 are analyzed in the temperature range
$T$ = 4.2–300 K and the magnetic field range
$B$ = 0.005–2.22 T. Using data on the
$R(B)$ in low and high magnetic fields and the data on
$\sigma(T)$, electron and hole concentrations and mobilities are determined. It is shown that the electron concentration
$n$ in the studied samples is almost independent of
$T$ in the range 4.2–15 K, while as
$T$ increases, it increases according to the law
$n\propto T^r$ (
$r>$ 3/2), where
$r = f(n, T, x)$. It is found that
$r$ varies from 1.7 at
$x$ = 0.1 to 3.1 at compositions with
$x$ = 0.14 and 0.15. The results for
$n(T)$ are compared with theory, taking into account nonparabolicity of the variance law for
$(T)$, and with the theory of impurity states in narrow-gap and zero-gap semiconductors. It is shown that the constancy of
$n(T)$ up to
$\sim$15 K and the strong dependence
$n(T)$ (
$r >$ 3/2) at higher temperatures are caused by the intense ionization of electrons localized at acceptor states.
Received: 17.05.2011
Accepted: 21.07.2011
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