Fabrications of different Sb content p-SnO2 thin films

Tin oxide (SnO2) is a wide-band-gap semiconductor with a bandwidth of 3.6 eV at room temperature, which is widely used in many fields, such as gas sensors, transparent electrodes and optoelectronic devices due to its high optical transparency, low resistivity, and higher chemical and physical stability. However for the real applications of SnO2 based optoelectronic devices, it is necessary to obtain both n-type and p-type SnO2 materials. Unfortunately, SnO2 is intrinsically an n-type semiconductor material, therefore most efforts have been made to obtain p-type SnO2 materials. In this paper, SnO2 thin films with different Sb12 concentrations are grown on Al2O3 substrates by chemical vapor deposition method through using Sb2O3 and SnO as reaction source. The surface morphology, elemental concentration, and structural properties of SnO2 thin films with different Sb concentrations are investigated by field-emission scanning electron microscopy, energy-dispersive spectroscopy and X-ray diffraction, respectively. As the Sb content increases, the SnO2 thin films become more smooth and the grain size increases, indicating that the crystal quality of the thin film is improved. It is also found small amount of Sb doping of SnO2 thin film can be act as a surfactant. Moreover, the Hall measurement results indicate that the Sb doped SnO2 thin film has a p-type conductivity for an optimum Sb2O3/SnO mass ratio of 1:5. The optical absorption spectrum measurement indicates that the energy gap of sample is evidently blue-shifted with increasing Sb doping concentration. Furthermore, the Sb doped p-SnO2/n-SnO2 thin film homojunction is successfully fabricated to verify the p-type conductivity of Sb doped SnO2. The Sb doped p-SnO2/n-SnO2 homojunction device shows good rectifier characteristics, and its forward-turn-on voltage is 3.4 V.