H. Bayhan et C. Ercelebi, ELECTRICAL CHARACTERIZATION OF VACUUM-DEPOSITED N-CDS P-CDTE HETEROJUNCTION DEVICES/, Semiconductor science and technology, 12(5), 1997, pp. 600-608
The effects of post-deposition processes such as CdCl2 dip and/or anne
aling in air on the material and device properties of vacuum-evaporate
d Au-CdTe/CdS-TO heterojunction solar cells have been investigated. Th
e CdCl2 dip followed by air annealing at 300 degrees C for 5 min impro
ved the device efficiency significantly, resulting in decreased CdTe r
esistivity and enhanced grain size. The temperature-dependent current-
voltage analysis indicated that above 280 K interface recombination do
minates the current transport mechanism for the as-grown samples, whil
e depletion region recombination starts to be dominant after annealing
the samples with CdCl2. Below 280 K multistep tunnelling is identifie
d to be the dominant transport mechanism. Frequency-dependent capacita
nce-voltage studies revealed that after annealing with CdCl2 the densi
ty of interface states decreases and the quality of the heterointerfac
e improves. The capacitance of the CdS/CdTe heterojunctions has been a
nalysed using a model based on the existence of a single dominant trap
level, identified at 0.40 eV above the valence band with a concentrat
ion of 5.1 x 10(15) Cm-3.