Carrier Lifetime Degradation and Regeneration in Gallium- and Boron-Doped Monocrystalline Silicon Materials

Abstract

In this article, carrier lifetime degradation phenomena on fired gallium-doped Czochralski-grown silicon (Cz-Si:Ga) and boron-doped float-zone silicon (FZ-Si:B) are observed. We examine lifetime degradation and regeneration as a function of illumination intensity and temperature and observe qualitatively similar degradation effects in both material classes, which are triggered by a fast-firing high-temperature step. Charge carrier injection, e.g., through illumination, is required to activate the defects responsible for degradation. The extent of degradation increases with increasing temperature, which is untypical for degradation effects reported before. Despite different degradation time constants are measured for Cz-Si:Ga and FZ-Si:B, the activation energies are for both materials in the narrow range (0.58 ±0.04) <b xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">eV</b> . The extracted activation energy is quite different compared with other degradation effects in silicon, suggesting a novel defect formation mechanism. Since the lifetime degradation is triggered by the fast-firing of the silicon wafers during the presence of a hydrogen-rich dielectric at the surface, the involvement of hydrogen in the defect reaction is very likely. During prolonged illumination at elevated temperature (135 °C), we observe a permanent regeneration of the lifetime, whereas at temperatures close to room temperature (36 °C), the defect deactivation is only temporary.