Abstract
Oxygen precipitation in silicon has been associated with a weak room temperature sub-bandgap luminescence emission at around 1600 nm. We show that the additional presence of iron impurities enhances this emission by an order of magnitude and results in a red shift of the peak luminescence by approximately 45 nm. We not only observe an increase in the luminescence emission with iron contamination level but also with the density and size of the oxide precipitates. Moreover, we provide evidence that the sub-bandgap luminescence emission increases proportionally with the concentration of iron segregated to oxide precipitates after high temperature (>700 °C) annealing and thus allows evaluation of the gettering efficiency of oxygen-containing precipitates. Annealing of iron-contaminated samples at low temperatures (550 °C) results in a considerable reduction in the interstitial iron concentration without changing the sub-bandgap luminescence, indicating that the sink to which iron diffuses depends upon temperature.
Highlights
Iron is known to be one of the most troublesome contaminants in silicon due to its capability to form minority carrier lifetime reducing defects [1, 2]
We showed that strained oxide precipitates give rise to a broad room temperature luminescence peak centred at ∼1600 nm increasing in intensity with the density of strained precipitates [10]
We investigate the impact of iron contamination on the room temperature luminescence emission of p-type Czochralski silicon (Cz–Si) containing oxide precipitates of different sizes
Summary
Iron is known to be one of the most troublesome contaminants in silicon due to its capability to form minority carrier lifetime reducing defects [1, 2]. Complete elimination of iron from silicon device manufacturing is challenging. As iron is a very common element in nature, it is found in lower purity silicon feedstock and can enter silicon during crystal growth and subsequent device processing. Methods have been developed to remove iron from active device regions.
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