Band offsets and optical conduction in the CdSe/GaSe interface

• The CdSe/GaSe interface is prepared by the physical vapor deposition technique.
• The Structural properties are investigated by the X-ray diffraction technique.
• The optical transmittance, reflectance, absorbance and conductance are explored.
• The conduction and valence band offsets are determined.
• The dielectric spectra are studied.
• The optical conductivity parameters are computed by Lorentz approach.

In this work, the design and characterization of CdSe/GaSe heterojunction is considered. The CdSe/GaSe thin film interface was prepared by the physical vapor deposition technique. Systematic structural and optical analysis were performed to explore the crystalline nature, the optical band gaps, the conduction and valence band offsets, the dielectric spectra, and the frequency dependent optical conductivity at terahertz frequencies. The X-ray diffraction analysis revealed a polycrystalline interface that is mostly dominated by the hexagonal CdSe oriented in the (002) direction. It was also found that the CdSe/GaSe interface exhibits conduction and valence band offsets of 1.35 and 1.23/1.14 eV, respectively. The dielectric spectra displayed two dielectric resonance peaks at 530 and 445 THz. Moreover, the computational fittings of the optical conductivity of the interface revealed a free carrier scattering time of 0.41 (fs) for a free carrier density of 7.0 × 1018 (cm−3). The field effect mobility for the CdSe/GaSe interface was found to be 5.22 (cm2/Vs). The remarkable features of this device having large band offsets and qualitative optical conduction dominated by a scattering time in the order of femtoseconds in addition to the dielectric property nominate the device to be used in optoelectronic technology.