A possible explanation for high quantum efficiency of PtSi/porous Si Schottky detectors

P-type PtSi/porous Si Schottky detectors exhibit efficiencies as large as 60% in 2 to 7 (mu) m spectral range. Such efficiencies are larger than theoretical limit for regular PtSi detectors, as predicted by the modified Fowler theory. In the porous detectors a thin PtSi layer covers the walls of the pores creating a Schottky junction with a random surface orientation at any given point with respect to the Si substrate. If we assume that the orientation of the junction surface changes in scales comparable to the mean free path of the photo-excited carriers and incorporate that into the orthodox theory, the chance of transferring excited carriers into the Si substrate increases drastically and the large efficiencies of the porous samples can partially be justified.