Structural, optical and electrical measurements on boron-doped CdO thin films

Several boron-doped CdO with different boron composition thin films have been prepared on glass substrate by a vacuum evaporation technique. The effects of boron doping on the structural, electrical and optical properties of the host CdO films were systematically studied. The X-ray diffraction study shows that some of B³⁺ ions occupied locations in interstitial positions and/or Cd²⁺-ion vacancies of CdO lattice. The band gap of B-doped CdO suffers narrowing by 30–38% compare to undoped CdO. Such band gap narrowing (BGN) was studied in the framework of the available models. Furthermore, a phenomenological evaluation of the dependence of band gap on the carrier concentration in the film samples is discussed. The electrical behaviours show that all the prepared B-doped CdO films are degenerate semiconductors. However, the boron doping influences all the optoelectrical properties of CdO. Their dc-conductivity, carrier concentration and mobility increase compare to undoped CdO film. The largest mobility of 45–47 cm²/V s was measured for 6–8% boron-doped CdO film. From near infrared transparent-conducting oxide (NIR-TCO) point of view, boron is effective for CdO donor doping.