Preferential Attachment of H in Amorphous Hydrogenated Binary Semiconductors and Consequent Inferior Reduction of Pseudogap State Density

Abstract

Hydrogen evolution and infrared vibrational absorption have been interpreted to show (1) the existence of weakly bonded H in $a$-Ge: H and Ge-rich $a$-Si-Ge: H alloys, and (2) a preference ratio in excess of 5 for the attachment of H to Si over Ge in the formation of such alloys. It is suggested that this may account for the inferior photoresponse of hydrogenated binaries compared to elements, and also for the superiority of $a$-Si: H over $a$-Ge: H. Some ideas on better compensators than H are advanced.