Low-temperature admittance measurement in thin film amorphous silicon structures

In this paper we analyze low-temperature admittance (capacitance and conductance) measurement as an effective tool for the characterization of amorphous silicon doped layers embedded in thin film structures. Temperature and frequency ranges of 20-250 K and 1-100 kHz, respectively, were used. Measurements were performed on p-i silver and p-i-n structures. Devices with different thicknesses, carbon, and boron content of the p-doped layer were examined. The evolution of the conductance of p-i-n solar cells under illumination was also investigated. Results show excellent sensitivity of the measurement to the states of the doped layer. This sensitivity is explained by using a finite difference simulation program, which proves that at low temperature the trapping process is spatially limited to the doped layers. (C) 1997 American Institute of Physics.