Wave Vector Excitation

Si is widely used in most of the electric devices; therefore, our world cannot be without Si. To improve the performance of Si devices using electron only as carriers, it is required to reduce the size of the device below 10 nm. In addition to the electrons, it is expected to improve further by introducing the photons [1]. However, Si is not good material for photonic device because Si has low efficiency to excite the carrier by the photo-excitation of propagating FF. This is due to its indirect bandgap, in which Si has different wave vector between the \(\Gamma \) point and the X point [2, 3] (refer to Fig. 2.8a). Therefore, phonon assistance is required to compensate for the wave vector difference.