New regime of RF PECVD for the growth of a-Si:H and its alloys with improved electronic properties

Abstract

a-Si:H and its alloy developed under a 'new regime' (/spl alpha/-/spl gamma/' transition zone) of discharge of RFPECVD and using strong helium dilution show lots of new characteristics. The value of /spl mu//spl tau/ of the resulting films is enhanced by a factor of 10 to 100 (independent of Fermi level position) and concomitantly the DOS above Fermi level of a-Si:H and a-SiGe:H ([Ge]/spl les/0.20) is much lower than that of standard samples. The carrier mobility measured by time resolved microwave conductivity (TRMC) is increased by a factor of 2 to 3. HRTEM micrograph shows the region of ordered structure (nanocrystal) embedded in an amorphous matrix. The reproducibility of this type of materials in different reactors has been confirmed. Thus, inclusion of ordered network structure in the amorphous matrix could be the new way to improve electronic properties of a-Si:H and its alloys.