Transient ambipolar charge distributions in amorphous and crystalline semiconductors

Time resolved photo- and thermoelectric effects (TTE) may be used to determine the heat diffusivity, carrier lifetimes, carrier mobilities and trap levels in crystalline and amorphous semiconductors. However, because generation and recombination processes are connected, the relaxation times in the different time regimes are interrelated. The same is true for the initial voltage of the transients and their decay time. In this contribution an analysis is attempted to reduce the experimental data for crystalline and amorphous silicon, in particular for the time regime where an ambipolar charge distribution in trap states has to be assumed. The calculation is compared with experiment for an n-layer hydrogenated amorphous silicon sample and one n-type crystalline silicon sample.