Ba. Mansour et Ma. Elhagary, ELECTRICAL-CONDUCTIVITY AND NEAR-INFRARED ABSORPTION OF CUGASE2 THIN-FILMS, Physica status solidi. a, Applied research, 146(2), 1994, pp. 669-673
Near-infrared absorption spectra at room temperature in the photon ene
rgy range hv approximate to 0.4 to 1.5 eV and electrical conductivity
(sigma) in the temperature range 300 to 450 K are measured for p-type
CuGaSe2 thin films. Two acceptor levels with ionization energies E(1)
(240, 270 meV) and E(2) (80, 90 meV) are found. The ionization energy
of accepters is also obtained from optical absorption measurements as
280 meV. Free carrier absorption below 0.5 eV is observed in which the
absorption coefficient alpha increases as the third power of the wave
length lambda and the carrier concentration dependence of alpha is sup
erlinear rather than linear in this region of photon energy. This abso
rption is associated with the ionized impurity scattering mechanism. A
n absorption band at hv approximate to 0.75 eV is also found, its peak
energy and value of alpha depend on the carrier concentration. This b
and may be due to the transition from a lower lying valence band to an
upper one.