Transport properties of glow-discharge amorphous silicon grown under different deposition conditions

Abstract

Abstract Hydrogenated amorphous silicon has been prepared using the glow discharge technique, with the deposition parameters being varied to give two sample groups. In the first case, substrate temperatures range from 130 to 350°C with a constant r.f. power setting. For the second group of samples, the substrate temperature is held constant at 290°C, and deposition rates of between 2 and 8 A s− 1 are used. The samples are compared on the basis of electron drift mobilities and mobility-lifetime products obtained from time-of-flight and charge collection experiments. Room-temperature mobilities are found to vary by an order of magnitude over the range of samples studied. Among the “poorer” samples, mobilities are found to be more strongly activated, indicating trapping to depths of 0.25 eV in the conduction-band tail. Transient photoconductivity data are used to derive the conduction-band-tail density of states. For samples produced under different deposition conditions, band-tail widths are found to increa...