Intersublevel Photoabsorption and Photoelectric Processes in ZnO Quantum Dot Embedded in and AlN Matrices

In this paper, we investigate the linear and nonlinear photoabsorption processes in the conduction-band-confined levels of a singly charged ZnO quantum dot (QD) surrounded by HfO₂ and AlN matrices. We also investigate the photoelectric process in which the conduction band electron ejects from the dot to the vacuum. We use the effective mass approximation with a finite barrier height at the dot-matrix interface. We consider the self-energy of the electron in the dot and the local field effect. The electromagnetic interaction of the incident radiation with the electron in the dot is considered in the electric dipole plus quadrupole approximation. Results for the photoabsorption coefficient and the photoelectric process are presented for different dot sizes and different intensities of incident radiation. It is found that the inclusion of the quadrupole effect reveals new photoabsorption peaks in the absorption spectra. Both the photoabsorption and photoelectric processes significantly depend on the dot size and the surrounding matrix. The change in the intensity of the incident radiation significantly influences the nonlinear photoabsorption. The photoabsorption coefficient and the photoelectric cross sections are found to be relatively higher for the ZnO QD embedded in the high-dielectric constant matrix HfO₂ as compared with the lower-dielectric constant AlN matrix.