Study of zinc oxide/porous silicon interface for optoelectronic devices

A study of the interface of the ZnO/PSi heterojunction with photoluminescense (PL), cathodoluminescense (CL) and Electron Beam Induced Current (EBIC) is presented. The fabrication process of the heterostructure consisted of three steps; First, it was formed the porous silicon (PSi) layer via electrochemical synthesis, it was followed by the growth of a ZnO thin film onto the Psi layer via RF-magnetron sputtering, Finally, a thermal annealing process at 700 °C was applied on the ZnO/PSi heterojunction device. The PL analysis revealed a widening of the luminescence spectrum (in a range of 350 to 850 nm) due to the application of a thermal annealing process which favored the crystallization of the ZnO/PSi structure. Monochromatic CL images were focused on the two main peaks of the CL spectra at 385 and 436 nm, showing the emission of the ZnO and the ZnO/PSi structure, respectively. EBIC characterization determined the electronic properties of the heterojunction such as deflection zone (50 nm) as well as the hole (Lp=55nm), and electron (Ln=60nm) diffusion lengths. Furthermore, EBIC characterization served to experimentally determined the density of donor impurity atoms in the ZnO film (Nd=3.75x1014cm−3).