Investigation of a buried double p-n junction structure implemented in CMOS technology for wavelength-sensitive detection

A buried double pn junction (BDJ) structure in a CMOS process has been investigated to validate a wavelength-sensing method, which consists in using the ratio of the deep junction current to the shallow junction current for wavelength determination. Theoretically, an analytical BDJ device model has been established; and experimentally a chip incorporating BDJ sensing elements as well as electronic circuitry has been designed and measured. Both simulated and measured results, which are in good agreement, confirm the monotonic increase of the spectral response of the ratio. This allows the dominant wavelength of the incident light to be identified.