Separation of doping density and minority carrier lifetime in photoluminescence measurements on semiconductor materials
First Claim
1. A method of conducting an analysis of a silicon ingot or brick, said method including the steps of:
- (a) exciting at least one side facet of said silicon ingot or brick to produce photoluminescence;
(b) obtaining at least one image of the photoluminescence emitted from said at least one side facet; and
(c) interpreting said at least one image to identify variations in effective and/or bulk minority carrier lifetime in said ingot or brick, wherein the step of interpreting said at least one image comprises normalising the photoluminescence intensity within said at least one image with regard to variations in the background doping density of said ingot or brick, to identify variations in effective minority carrier lifetime in said ingot or brick.
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Abstract
Methods are presented for separating the effects of background doping density and effective minority carrier lifetime on photoluminescence (PL) generated from semiconductor materials. In one embodiment the background doping density is measured by another technique, enabling PL measurements to be analyzed in terms of effective minority carrier lifetime. In another embodiment the effective lifetime is measured by another technique, enabling PL measurements to be analyzed in terms of background doping density. In another embodiment, the effect of background doping density is removed by calculating intensity ratios of two PL measurements obtained in different spectral regions, or generated by different excitation wavelengths. The methods are particularly useful for bulk samples such as bricks or ingots of silicon, where information can be obtained over a much wider range of bulk lifetime values than is possible with thin, surface-limited samples such as silicon wafers. The methods may find application in solar cell manufacturing.
7 Citations
21 Claims
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1. A method of conducting an analysis of a silicon ingot or brick, said method including the steps of:
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(a) exciting at least one side facet of said silicon ingot or brick to produce photoluminescence; (b) obtaining at least one image of the photoluminescence emitted from said at least one side facet; and (c) interpreting said at least one image to identify variations in effective and/or bulk minority carrier lifetime in said ingot or brick, wherein the step of interpreting said at least one image comprises normalising the photoluminescence intensity within said at least one image with regard to variations in the background doping density of said ingot or brick, to identify variations in effective minority carrier lifetime in said ingot or brick. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A method of conducting an analysis of a silicon ingot or brick, said method including the steps of:
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(a) exciting at least one side facet of said silicon ingot or brick to produce photoluminescence; (b) obtaining at least one image of the photoluminescence emitted from said at least one side facet; and (c) interpreting said at least one image to identify variations in effective and/or bulk minority carrier lifetime in said ingot or brick, wherein the at least one photoluminescence image is used as a cutting guide in wafer production, or as a guide in wafer production to sort wafers into quality bins.
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13. A method of conducting an analysis of a silicon ingot or brick, said method including the steps of:
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(a) exciting at least one side facet of said silicon ingot or brick to produce photoluminescence; (b) obtaining at least one image of the photoluminescence emitted from said at least one side facet; and (c) interpreting said at least one image to identify variations in effective and/or bulk minority carrier lifetime in said ingot or brick, wherein the information obtained from said method is used in the manufacturing of silicon bricks or ingots, or to determine the price of wafers derived from said ingot or brick, or to obtain feedback on feedstock quality in the production of silicon wafers.
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14. A system for conducting an analysis of a silicon ingot or brick, said system comprising:
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a photodetection unit for obtaining at least one image or line scan of photoluminescence generated from at least one side facet of said silicon ingot or brick; and a processor for interpreting said at least one photoluminescence image or line scan to identify variations in effective and/or bulk minority carrier lifetime in said ingot or brick wherein said processor is adapted to normalise the photoluminescence intensity within said at least one photoluminescence image or line scan with regard to variations in the background doping density of said ingot or brick, to identify variations in effective minority carrier lifetime in said ingot or brick. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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21. A system for conducting an analysis of a silicon ingot or brick, said system including:
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a photodetection unit for obtaining at least one image or line scan of photoluminescence generated from at least one side facet of said silicon ingot or brick; and a processor for interpreting said at least one photoluminescence image or line scan to identify variations in effective and/or bulk minority carrier lifetime in said ingot or brick, wherein said processor is adapted to obtain information from said at least one photoluminescence image for use as a cutting guide in wafer production, or in the manufacturing of silicon bricks or ingots, or in determining the price of wafers derived from said ingot or brick, or as a guide in wafer production for sorting wafers into quality bins, or in obtaining feedback on feedstock quality in the production of silicon wafers.
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Specification