Correlated carrier transport and optical phenomena in CdO layers grown by plasma-assisted molecular beam epitaxy technique

In this work, we have investigated a series of CdO layers grown by the plasma-assisted molecular beam epitaxy technique on the m-plane sapphire substrate. The relation between Cd and O2 parameters during growth in-fluences the stoichiometry of the CdO layers and it affects morphological, optical, and electrical properties which are manifested in the roughness parameter, lattice constant, optical bandgap, and electrical parameter of the layers. The surface morphology and structural properties of CdO layers were studied using atomic force mi-croscopy and X-ray diffraction respectively. Temperature-dependent Hall measurement revealed the maximum mobility of 352 cm2V- 1s- 1 achieved at room temperature with a carrier concentration of about 4.5 x 1019 cm-3. The optical properties and bandgap of CdO layers were investigated using UV-Visible spectroscopy at room temperature. It is observed that the shift of the bandgap depends upon the carrier concentration and is acquired by combining the effect of bandgap widening and bandgap narrowing.