High quality thin film Cu (In, Ga) Se2 for semiconductor device by vapor phase recrystallization

摘要

Enhanced quality thin films of Cuw(In,Gay)Sez for semiconductor device applications are fabricated by initially forming a Cu-rich, phase-separated compound mixture comprising Cu(In,Ga):CuxSe on a substrate to form a large-grain precursor and then converting the excess CuxSe to Cu(In,Ga)Se2 by exposing it to an activity of In and/or Ga, either in vapor In and/or Ga form or in solid (In,Ga)ySez. Alternatively, the conversion can be made by sequential deposition of In and/or Ga and Se onto the phase-separated precursor. The conversion process is preferably performed in the temperature range of about 300 DEG -600 DEG C., where the Cu(In,Ga)Se2 remains solid, while the excess CuxSe is in a liquid flux. The characteristic of the resulting Cuw(In,Ga)ySez can be controlled by the temperature. Higher temperatures, such as 500 DEG -600 DEG C., result in a nearly stoichiometric Cu(In,Ga)Se2, whereas lower temperatures, such as 300 DEG -400 DEG C., result in a more Cu-poor compound, such as the Cuz(In,Ga)4Se7 phase.