Improvement of the surface quality of semi-insulating InP substrates through a novel etching and cleaning method

Abstract

Residual impurities and contamination on semi-insulating (SI) InP wafers are detrimental for epitaxial growth and device performance, especially because residual silicon on an SI-InP wafer surface is electrically active and generates an n-type conduction layer at the interface between the epilayer and the InP substrate. In order to reduce the concentration of Si and improve surface quality, the authors investigate a wet-chemical cleaning process for ready-to-use InP substrates. A novel and practical cleaning process was developed by adding an alkaline solution to the conventional acidic cleaning process. Time-of-flight secondary mass spectrometry, a very powerful analysis technique to characterize surfaces and investigate any organic and inorganic contamination present on the InP surface, was used after the samples were etched under different cleaning processes. The results show that the novel etching process effectively reduces the Si contamination.