Increasing minority carrier lifetime in as-grown multicrystalline silicon by low temperature internal gettering

Journal Article · Tue Jun 21 04:00:00 EDT 2016 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4954010· OSTI ID:22596824

We report a systematic study into the effects of long low temperature (≤500 °C) annealing on the lifetime and interstitial iron distributions in as-grown multicrystalline silicon (mc-Si) from different ingot height positions. Samples are characterised in terms of dislocation density, and lifetime and interstitial iron concentration measurements are made at every stage using a temporary room temperature iodine-ethanol surface passivation scheme. Our measurement procedure allows these properties to be monitored during processing in a pseudo in situ way. Sufficient annealing at 300 °C and 400 °C increases lifetime in all cases studied, and annealing at 500 °C was only found to improve relatively poor wafers from the top and bottom of the block. We demonstrate that lifetime in poor as-grown wafers can be improved substantially by a low cost process in the absence of any bulk passivation which might result from a dielectric surface film. Substantial improvements are found in bottom wafers, for which annealing at 400 °C for 35 h increases lifetime from 5.5 μs to 38.7 μs. The lifetime of top wafers is improved from 12.1 μs to 23.8 μs under the same conditions. A correlation between interstitial iron concentration reduction and lifetime improvement is found in these cases. Surprisingly, although the interstitial iron concentration exceeds the expected solubility values, low temperature annealing seems to result in an initial increase in interstitial iron concentration, and any subsequent decay is a complex process driven not only by diffusion of interstitial iron.

• OSTI ID: 22596824
• Journal Information: Journal of Applied Physics, Journal Name: Journal of Applied Physics Journal Issue: 23 Vol. 119; ISSN JAPIAU; ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ABUNDANCE
ANNEALING
CARRIER LIFETIME
CARRIERS
CONCENTRATION RATIO
DIELECTRIC MATERIALS
DISLOCATIONS
ETHANOL
GETTERING
IODINE
IRON
PASSIVATION
SILICON
SURFACES
TEMPERATURE RANGE 0065-0273 K
TEMPERATURE RANGE 0273-0400 K