A novel CMOS spectrometer based on wavelength absorption

This article reports on a novel spectrometer without dispersing elements fabricated in standard CMOS technology. The spectrum detection principle is based on the wavelength absorption mechanism in silicon. A finite element model confirms the excess holes' detection principle as a function of depth where moving holes' trajectory is deviated under the Lorentz force towards a set of collectors. In the case of high excess carrier concentration, experimental results confirm the theoretical analysis that wavelength becomes indistinguishable because the Auger recombination mechanism is dominant, which should be avoided to realize a spectrometer. For the low excess carrier concentration case, the concentration profile is determined by the incident irradiance and the wavelength and can be additive since the Shockley-Reed-Hall recombination mechanism prevails, where the excess carrier life time is constant, and hence suitable for wavelength discrimination. In order to realize a spectrometer, a light spectrum detection method is developed, which requires a linear equation set where coefficients of the matrix coming from the measurement of the current density as a function of the irradiance for different wavelengths and magnetic fields. The proposed miniature and integrated spectrometer with a pixel array can be used as a spectral imager.