SEPARATION OF DOPING DENSITY AND MINORITY CARRIER LIFETIME IN PHOTOLUMINESCENCE MEASUREMENTS ON SEMICONDUCTOR MATERIALS
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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 analysed in terms of effective minority carrier lifetime. In another embodiment the effective lifetime is measured by another technique, enabling PL measurements to be analysed in terms of background doping density. In yet 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 for improving the manufacture of silicon ingots and bricks, or for providing a cutting guide for wafering.
15 Citations
81 Claims
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1-39. -39. (canceled)
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40. A method of conducting an analysis of a semiconductor material, said method including the steps of:
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(a) exciting said material to produce photoluminescence; (b) measuring the intensity of the photoluminescence emitted from said material; (c) normalising the measured photoluminescence intensity with regard to variations in the background doping density of said material to obtain a normalised photoluminescence intensity; and (d) analysing said normalised photoluminescence intensity in terms of one or more properties of said material. - View Dependent Claims (41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 58)
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54. A system for conducting an analysis of a semiconductor material, said system including:
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a photodetection unit for obtaining at least one image or line scan of photoluminescence generated from a surface of said material; and a processor for normalising the measured photoluminescence intensity with regard to variations in the background doping density across said surface, and for analysing the normalised photoluminescence intensity in terms of one or more properties of said material. - View Dependent Claims (55, 56, 57)
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59. A method of conducting an analysis of a semiconductor material, said method including the steps of:
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(a) exciting a portion of said material to produce photoluminescence; (b) measuring the distribution of the photoluminescence emitted from said portion; (c) normalising the measured photoluminescence distribution with regard to variations in the effective minority carrier lifetime across said portion; and (c) analysing the normalised photoluminescence distribution in terms of variations in the background doping density of said material across said portion. - View Dependent Claims (60, 61, 62, 63, 64, 65, 66, 67, 68, 73)
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69. A system for conducting an analysis of a semiconductor material, said system including:
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a photodetection unit for obtaining at least one image or line scan of photoluminescence generated from a surface of said material; and a processor for normalising the measured photoluminescence intensity in each part of said image or line scan with regard to variations in the effective minority carrier lifetime across said surface, and for analysing the normalised photoluminescence image or line scan in terms of variations in the background doping density across said surface. - View Dependent Claims (70, 71, 72)
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74. A method of conducting an analysis of a semiconductor material, said method including the steps of:
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(a) exciting a portion of said material to produce photoluminescence; (b) measuring the distribution of the photoluminescence emitted from said portion; and (c) analysing the photoluminescence distribution in terms of variations in the background doping density of said material across said portion. - View Dependent Claims (75, 76, 77, 78, 79, 80, 81)
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Specification