Iron-related carrier traps near the n⁺p-junctions of crystalline silicon solar cells: impacts of feedstock and of the fabrication processes

Abstract

An influence of the iron content in the crystal on the formation of carrier traps in the silicon solar cells was studied. Mesastructured n þ p-junctions were formed on the surface of Cz-Si wafers after various stages of a standard solar cell fabrication process. Majority carrier traps in/near the junction volume were investigated by deep level transient spectroscopy (DLTS). The trap density correlated with the total iron content in the wafers and dropped strongly with the distance from the junctions. Our results suggest that the traps were formed during the phosphorus diffusion process and/or during the subsequent cooling. The initial iron content in the wafers influenced changes in the trap concentrations at further fabrication steps. The present study could help in increasing solar cell efficiencies by tailoring the fabrication processes according to the contamination in the feedstock.

Capacitance Transient Spectroscopy Measurements on High-k Metal Gate Field Effect Transistors Fabricated Using 28nm Technology Node

“…All previous CTS studies were conducted on samples prepared in laboratory conditions with MIS capacitors of relatively large areas (several mm 2 ). Recently, it was shown that standard DLTS investigation on finished devices [12][13][14] can bring new and important information about carrier traps, which cannot be obtained on samples prepared under laboratory conditions. Detection of a new type of iron-related defects (near-junction volume, NJV traps) [13] and traps related to lightinduced degradation [14] became possible only due to investigation of finished solar cell structures, without significant modification of their structure and properties.…”

“…Recently, it was shown that standard DLTS investigation on finished devices [12][13][14] can bring new and important information about carrier traps, which cannot be obtained on samples prepared under laboratory conditions. Detection of a new type of iron-related defects (near-junction volume, NJV traps) [13] and traps related to lightinduced degradation [14] became possible only due to investigation of finished solar cell structures, without significant modification of their structure and properties. The aim of the present work was to investigate the applicability of CTS to structures fabricated under production conditions, with real dimensions of the working elements and after application of the full cycle of production processes, including the packaging.…”