Abstract
Thin amorphous films of Ge
5
As
22
Te
73–
x
In
x
(where
x
= 0, 3, 6 and 9 at. %) were thermally evaporated on glass substrates. The Seebeck coefficient (
S
) or simply thermoelectric power, dc electrical conductivity (
σ
d
), and photoconductivity (
σ
ph
) were measured within the temperature (
T
) range 300–420 K on the prepared thin films. The activation energies for dark conduction (∆
E
d
), thermoelectric (∆
E
S
) and photoconduction (∆
E
ph
) were estimated using the values of
σ
d
,
S
, and
σ
ph
, respectively. The current density (
J
) is found to be directly proportional to applied electric field (
E
) for the thin films indicating Ohmic behavior for
E
< 10
5
V/m. The positive values for
S
indicate that the semiconductor Ge
5
As
22
Te
73–
x
In
x
thin films are of p-type in the whole studied temperature range. It was found that
σ
d
and
σ
ph
increase, whereas
S
decreases with increasing In content. The energy gap (
E
g
) has been estimated from the spectral distribution of the dc-photoconductivity. The peak of photocurrent moves to lower spectrum energy when increasing In content from 0 to 9 at%. corresponding to a decrease in
E
g
from 1.1 to 0.9 eV. The dark conductivity pre-exponential factor (
σ
o
) was estimated by the variation of
σ
d
with both
T
and
S
.