CONDUCTION AND VALENCE-BAND PHOTOEMISSION MECHANISMS IN 2-DIMENSIONAL-3-DIMENSIONAL STRUCTURES

The active layers in heterojunction internal photoemission infrared detectors are always of thickness in the order of few hundred angstrom, and thus the behavior of the excited carriers should be described in a two-dimensional (2D) mode. Conduction and valence band photoemission mechanisms have been introduced in 2D-three-dimensional structures. The carrier behaviors of two carrier types, electron and hole, were discussed in the cases of PtSi/p-Si and p+-SiGe/p-Si, respectively. Parallel momentum conservation were well preserved for these two cases during carrier transportation across the heterojunction ballistically. Theoretical simulations were in good agreement with experimental data for both the electron and hole cases. The reason why p+-SiGe/p-Si photodiodes exhibit higher quantum efficiency than PtSi/p-Si diodes has also been discussed.