Fabrication of ultra-thin Ge epitaxial templates for Ⅲ-Ⅴ semiconductor solar cells

Abstract

Recently, sustainable eco-friendly renewable energy has been attracting attention due to serious climate change problem. In particular, among various renewable energies, energy converted from abundant solar energy is considered as a realistic alternative. Ⅲ-Ⅴ semiconductor solar cells are known as promising technologies in eco-friendly renewable energy with excellent light conversion efficiency and electrical properties based on direct band gap, resistance to extreme environments and radiation. However, despite these advantages, due to the high manufacturing cost of Ⅲ-Ⅴ semiconductor solar cells, applications are limited to markets that are less affected by cost such as space industry and military industry. Ge and GaAs, the growth substrates for the manufacture of Ⅲ-Ⅴ semiconductor solar cells, account for about 40% of the total solar cell manufacturing cost. Therefore, if the cost of the substrate is reduced, the total solar cell manufacturing cost can be significantly reduced. In this dissertation, the thinning and reuse technology of Ge, a material used for epitaxial growth of Ⅲ-Ⅴ semiconductor solar cells, was studied to reduce the cost of Ⅲ-Ⅴ semiconductor solar cells. We reduced the process cost and made it possible to manufacture a large area by changing the deep reactive ion etching (DRIE) process for porous structure formation of the Germanium-on-nothing (GON) technology, which has been previously studied, to the bipolar electrochemical etching process. In this study, a uniform porous layer with a thickness of 1μm or more was formed through a bipolar electrochemical etching process, and a thin film for GaAs solar cell growth was formed by reorganization of the porous layer formed through the electrochemical process at high temperature. The substrate thinning and reusing technology developed through this study can be used in the next-generation space and military industry that require flexibility and small volume in the future, and is expected to enable the production of low-cost, high-efficiency solar cells.