The analysis further suggests that the carrier multiplication process in thin a-Si can be much more efficient than in thick a-Si, even stronger than single crystalline Si in some cases. We further justified the application of local field model for thin a-Si, based on the property that in a-Si, the mean-free path for energy relaxation is orders of magnitude greater than the mean-free-path for momentum relaxation.
We modeled the gain mechanism in a-Si by solving the transport equations including dynamics of defect states and carrier multiplication via the local field model. We also show presence of trap-induced junction modulation at much lower frequency. We show evidence of highly effective carrier multiplication process within a-Si as the primary gain mechanism, especially at high frequency. To unveil the true gain mechanism, we performed theoretical modeling and numerical analysis along with experimental data at different frequencies. Recently, amorphous Silicon (a-Si) photodiodes with thin a-Si layer (∼40 nm) have shown a gain-bandwidth product of over 2 THz with very low excess noise and also have been used as a gain media in a cascaded system with single photon sensitivity. Surprisingly, some disordered materials showed photocurrent amplification not by conventional photoconductive gain. Amorphous materials have low mobility due to their nature of disorder.
0 kommentar(er)
