Generation lifetime in amorphous silicon as determined by MOS admittance measurements

Capacitance-voltage measurements are performed in order to investigate dynamical properties of the undoped layer of an amorphous silicon pin solar cell. A special MOS diode is prepared which allows the determination of the resistivity, the net carrier concentration, and the doping density in the i-layer. The C-V measurements indicate two clearly distinguishable dispersion behaviors in accumulation and inversion of the (slightly n-type doped) i-layer of the diode and inversion built-up. A numerical simulation computes the potential variation inside the sample, taking into account the trap density in the a-Si:H. A complete set of CV curves under quasistatic conditions is simulated and fitting to the experimental data yields the actual trap density. This information granted, one can calculate the generation lifetime of carriers in the depleted region of this diode biased to inversion