IMPROVEMENT IN THE PROPERTIES OF A-SIGE-H FILMS - ROLES OF DEPOSITIONRATE AND HYDROGEN DILUTION

Device quality a-SiGe:H thin films have been deposited by radio-freque ncy plasma-assisted decomposition of silane and germane diluted with a nd without hydrogen Improvement in structural and electronic propertie s have been achieved employing low deposition rate and high hydrogen d ilution. It has been observed that low deposition rate can reduce the preferential attachment of H to silicon throughout the alloy region wh ile the beneficial effect of hydrogen dilution is more effective in a low band gap region (E(g) less-than-or-equal-to 1.40 eV). The photocon ductivities of the good quality a-SiGe:H alloy films under white light illumination (50 mW/cm2) are 1.34 X 10(-4) S cm-1 and 1.9 X 10(-5) S cm-1 at the optical gaps ot' 1.51 and 1.35 eV, respectively. The chang es in midgap defect density and tail states have been correlated with the photoconductivities of the samples deposited under different condi tions. An attempt has been made to explain the results from the growth kinetics of the films.