Application of scanning mid-IR-laser microscopy for characterization of semiconductor materials for photovoltaics

TL;DR

This paper demonstrates the effective use of scanning mid-IR-laser microscopy for characterizing semiconductor materials like CZSiGe and multicrystalline silicon, revealing defect structures and carrier scattering mechanisms relevant to photovoltaics.

Contribution

The study extends the application of scanning mid-IR-laser microscopy to new photovoltaic materials and clarifies the origin of anomalous scattering signals in polished samples.

Findings

Effective imaging of polishing-induced defects and pin holes.

Attribution of cubic power dependence to carrier scattering on dislocations.

Validation of the technique as a defect investigation tool for photovoltaic materials.

Abstract

The scanning mid-IR-laser microscopy was previously demonstrated as an effective tool for characterization of different semiconductor crystals. Now the technique has been successfully applied for the investigation of CZ SixGe1-x -- a promising material for photovoltaics - and multicrystalline silicon for solar cells. In addition, this technique was shown to be appropriate for imaging of polishing-induced defects as well as such huge defects as "pin holes". Besides, previously unexplained "anomalous" (cubic power) dependence of signal of the scanning mid-IR-laser microscope in the optical-beam-induced light scattering mode on the photoexcitation power obtained for mechanically polished samples has now been attributed to the excess carrier scattering on charged linear defects, likely dislocation lines. The conclusion is made in the article that the scanning mid-IR-laser microscopy may serve as very effective tool for defect investigations in materials for modern photovoltaics.