Spectral sensitivity of IR photodetectors in monolithic bipolar integrated circuits

We examine different designs for photodetectors within bipolar monolithic integrated circuits and study their spectral characteristics. We have analyzed the effect of buried n+-type layers in the photosensitive region of the photodiode on its spectral sensitivity. We show that the highest maximum spectral sensitivity in the IR region of the spectrum is exhibited by a tandem photodetector and an n+-n-p epitaxial photodiode.