Abstract
A recombination active defect is found in as-grown high-purity floating zone n-type silicon wafers containing grown-in nitrogen. In order to identify the properties of the defect, injection-dependent minority carrier lifetime measurements, secondary ion mass spectroscopy measurements, and photoluminescence lifetime imaging are performed. The lateral recombination center distribution varies greatly in a radially symmetric way, while the nitrogen concentration remains constant. The defect is shown to be deactivated through high temperature annealing and hydrogenation. We suggest that a nitrogen-intrinsic point defect complex may be responsible for the observed recombination.
Highlights
T HE presence of interstitial oxygen has been shown to negatively affect the minority carrier lifetime in silicon devices either through the boron–oxygen defect [2], [3], thermal donors [4], [5], other grown-in defects [6] or as a consequence of high temperature processing [7]–[11]
While the lifetime is initially lower in the nitrogen-doped wafers, we show that it improves after high temperature annealing to values similar to the nitrogen-lean wafers
We show that one defect or multiple defects limit(s) the lifetime in highly pure nitrogen-doped n-type floating zone silicon wafers
Summary
T HE presence of interstitial oxygen has been shown to negatively affect the minority carrier lifetime in silicon devices either through the boron–oxygen defect [2], [3], thermal donors [4], [5], other grown-in defects [6] or as a consequence of high temperature processing [7]–[11]. There is a growing interest in the photovoltaic community in using oxygen-lean growth methods, such as the floating-zone (FZ) method to produce wafers for high-efficiency silicon solar cells. Nitrogen is well known to mitigate the impact of extended defects [13]–[15]. It effectively suppresses the formation of vacancy and interstitial aggregates in FZ crystals [13], [14] (by reacting with vacancies and silicon interstitials via the reactions N2 + V → N2 V and N2 V + I → N2 ) [16]. Nitrogen pins dislocations [15], improving me-
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