Electrical conductivity control in transparent p-type (LaO)CuS thin films prepared by rf sputtering

Thin films of wide-gap p-type (LaO)CuS were prepared by rf sputtering followed by postannealing. Undoped (LaO)CuS films are electrically insulating and emit ultraviolet (UV) light arising from excitons at room temperature upon photoexcitation. The hole carrier concentration in the film was controlled in the range similar to10(15) to similar to10(20) cm(-3) by doping Sr2+ ions to replace La3+. The hole concentration reached a maximum of 2.7x10(20) cm(-3) at a doping level of 3 at. % Sr2+ ions, and then the carrier generation efficiency was similar to50%. These results demonstrate that the (La1-xSrxO)CuS films are potentially applicable to optoelectronic devices operating at short wavelengths because a transparent p electrode, as well as UV-emitting layers, may be fabricated using this material by controlling the doping level. (C) 2002 American Institute of Physics.