Electrical properties of thin-film semiconductor heterojunctions $n$-TiO$_2$/$p$-CuInS$_2$

Anisotype thin-film heterojunctions $n$-TiO$_2$/$p$-CuInS$_2$ are fabricated by spray-pyrolysis and dc reactive magnetron sputtering. The electrical and optical properties of thin CuInS$_2$ films deposited by spraypyrolysis in strictly controlled modes are examined. Also, the electrical properties of the Mo/CuInS$_2$ rear contact are studied by means of measurements by the three-probe method. The dominant charge transport mechanism in forward- and reverse-biased thin-film heterojunctions $n$-TiO$_2$/$p$-CuInS$_2$ is determined. This mechanism is well interpreted in terms of the tunneling-recombination model via surface states at the heterointerface and defects in the space-charge region.