Adjacent compensated codoping (alloying) of semiconductor films and its application to CdTe and CdS

Abstract

Current optoelectronics technology is based on semiconductors containing impurities with specific functionalities. Because of its relevance, research on novel methods to overcome difficulties on doping semiconductors continues being an important and active field theoretical and experimentally. In this work, the concept of adjacent compensated codoping is introduced and analyzed as an alternative method to tailor the materials´ properties via the controlled incorporation of two different types of impurities. This novel paradigm consists of selecting the first dopant adjacent in the periodic table to a chemical element forming the host, and the second impurity adjacent to another element of the host. This is done in a compensated manner: one is a p-type impurity and the other n-type. With this approach the structural and lattice dynamics properties of the host are marginally affected, while significant effects may be produced in its electrical and photoelectronic properties. The likeness in atomic masses, ionic radii and electronegativities between the host´s atoms and the adjacent codopants produces excellent solubilities. The application of this method to relevant semiconductors in photovoltaics such as CdTe, CdS and ZnO in the form of thin films is presented. A common feature in CdTe and CdS with adjacent compensated codopants was the existence of optimal concentrations for which the photoconductivity was significantly enhanced.