Optical, Structural and Morphological Characterization of a Zn-Doped GaAs Semiconducting Thin Film Produced by Thermionic Vacuum Arc

A 780 nm thick Zn-doped GaAs p-type semiconducting film was deposited onto a glass substrate under a high vacuum condition by means of the thermionic vacuum arc technique in a very short period of time (90 sec) using GaAs and Zn pellets as source materials. In order to characterize the produced film, the optical constants and absorbance of the film were measured using optical methods. By using the obtained optical absorbance data, the optical band gap was estimated from the Tauc plot based on the relation (alpha hv)(2) = B(hv - E-g). The refractive index value of the film was 3.73 at lambda = 632.8 nm. The band gap was estimated to be 1.35 eV. According to the results obtained from the FESEM and AFM related studies, the produced film displayed a granular surface morphology with a root mean square roughness of 17 nm. Contact angle measurements of several testing liquids were used to characterize the film in terms of wettability. It was found that the contact angle value was dependent on the liquid used. However, the film was hydrophilic as observed in contact angle measurements.