Carrier transport characteristics in PbSrSe thin films grown by molecular beam epitaxy

The dark-current characteristics of PbSrSe thin films grown by molecular beam epitaxy on BaF2 substrates with Sr composition from 0.066 to 0.276 have been measured systematically under different temperatures from 77 K to 300 K. The carrier-transport characteristics have been explained on the basis of a grain-boundary barrier model. The barrier height is found to be strongly related to the Sr composition. The different conductance behavior among the PbSrSe thin films is due to the variation of the grain-boundary barrier. Both the experimental barrier height, determined from the temperature-dependent conductance, and the theoretical results, deduced from the Poisson equation, reveal that the barrier height decreases with increasing applied bias. Furthermore, the success in explaining the observed negative-capacitance phenomenon gives further evidence that the accumulation of electrons at the grain boundaries plays a key role in the carrier transport of the PbSrSe thin films.