Passivation of Germanium Surfaces by a Quinhydrone–Methanol Solution Treatment

Abstract

The bulk lifetime of minority carriers, b , in germanium (Ge) is one of the most important material parameters in the design and fabrication of Gebased solar cells. Surface passivation of Ge substrates is indispensable to the accurate evaluation of b . We have found that a newly developed wet chemical treatment, quinhydrone-methanol (Q/M) solution treatment, effectively passivates Ge surfaces, achieving a surface recombination velocity (S) of less than 20 cm/s. It has been clarified that oxide layers containing the molecules from the Q/M solution were formed on the Ge surfaces treated with the Q/M solution. Ge dangling bonds (DBs) are thought to be terminated by these oxygen related molecules. Band bending in the Ge substrates induced by the oxide layers adsorbed on the Q/M-treated Ge surface can contribute to the reduction in S. We also briefly discuss the properties of a recombination center found in the bulk of highly resistive Ge substrates. #