Method of Using DC Photocurrent Measurements to Sense Wavelength or Color of Light or to Characterize Semiconductor Materials
Figure 1. Absorption coefficient versus wavelength for amorphous silicon. The data points were established using the invented method and the dashed line represents approximate values reported in literature.
Figure 2. Depletion width versus reverse bias. Shown are the results of both stsandard capacitance-voltage measurements (closed circles) and the invented method (solid line).
Figure 3. Color chart showing the actual color (open circles) of an incident light source and its estimated color (closed circles) as determined by the invented method. A novel method has been developed to characterize specific material properties of semiconductors by using DC photocurrents produced in a photodetector. The method also permits determination of the wavelength or the color of incident light.
Applications Spectrometry, fiber optic communications, and automated industries. Main Advantages The new method expands the use of a photodiode by permitting determination of specific properties such as absorption coefficient, depletion region width, and doping density of semiconductors. These parameters are obtained from the DC photocurrent response of a photodetector when a monochromatic light is exposed to the device. The new technique also allows inferring color or wavelength of an unknown incident light. The sensors, along with the associated electronic circuitry, can be fabricated in a semiconductor chip. This offers advantages over the conventional methods where the systems are bulky and expensive.
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