High quality tunneling oxides for passivated contacts and heterojunctions for high efficiency silicon solar cells

We analyze the chemical passivation quality of silicon oxide-nanolayers on crystalline silicon wafers prepared by different oxidation methods with surface photo voltage and quasi-steady-state photo conductance measurements. It is shown that for wet chemical oxidation and plasma oxidation, adequate passivation of the interface defects is achieved by subsequent anneal in forming gas environment. Furthermore, we present a simple oxidation method by means of rapid thermal oxidation, which requires no complex surface pre-treatment or surface pre-conditioning after cleaning. By rapid thermal oxidation (RTO) in a gaseous mixture of argon and oxygen and subsequent anneal in forming gas, a reproducible preparation method of high-quality ultra-thin oxide-nanolayers with a nearly intrinsic energetic distribution of interface states and a defect density of states of only 1 × 1012 cm^-2 eV^-1 at the minimum of the distribution is demonstrated.