A Simplified Thermal Diffusion Process for Making the Silicon p-n Junction Using Sol-Gel Thin Films as the Educational Application

Abstract

Learning by the actual experience of fabrication and evaluation of a p-n junction is a very effective way for students to obtain a deep meaningful understanding of the fundamentals of semiconductor physics. To achieve this requirement at a real-world classroom situation, a simplified fabrication process for making the silicon p-n junction as the educational application was studied. The process without using the lithography process, and in use of simple thermal diffusion furnace under the air environment for the impurity thermal diffusion process by using phosphorous silicate glass (PSG) thin film prepared by the Sol-Gel material as the phosphorus (P) diffusion source was proposed and tested. As the results, it was obtained that the impurity concentration and diffusion depth were controlled well by this method, and good rectification phenomenon of the p-n junction was successfully observed. The typical diode factor n of the p-n junction was approximately 2.3. The p-n junction also performed well as a solar cell. The FF is approximately 0.7. These results show that it is possible to use the p-n junction prepared by this simplified process as the educational device to help students’ understanding of the theory of the p-n junction.