Showing papers by "Miro Zeman published in 1996"

Electrical and optical properties of plasma‐deposited a‐SiGe:H alloys: Role of growth temperature and postgrowth anneal

Abstract: Basic properties of hydrogenated amorphous silicon–germanium (a‐SiGe:H) alloys deposited by plasma‐enhanced chemical‐vapor deposition were studied. We found that there is an optimal growth temperature in the range 250–280 °C. Infrared‐absorption spectra measurements show that in this temperature range the alloys have optimal composition of hydrogen content and bonding, providing a minimum in dangling bond defect density Ns and a high photoconductivity σph. Growth at lower temperatures results in hydrogen‐rich alloys with high Ns. Hydrogen in these alloys is mainly bonded as SiH2 and as clusters on internal voids. Growth at temperatures above the optimal value gives less deterioration of the properties of a‐SiGe:H than the growth below this optimal temperature. We found two different dependencies of σph on Ns: in optimized alloys σph changes proportionally to N−1s and in low‐temperature alloys σph decreases more steeply with N−1s due to a decrease in electron mobility. It is shown that annealing of a‐SiGe:...