Charge-transport properties of dendritic germanium thin films

The charge transport properties of dendritic Ge thin films on glass substra tes before and after postannealing have been studied by the methods of temp erature-dependent electrical conductivity measurements and temperature-depe ndent Hall mobility measurements. Results showed that the dendritic structu re is consistent with a crystalline matrix consisting of a high density of structural defects that cause degenerate conduction at high temperatures. P ostannealing of the as-prepared samples at a temperature greater than or eq ual to 570 degrees C for 2 h succeeded in converting the degenerate conduct ion into a nondegenerate one. All the samples were found to be p-type in th e low-temperature regime (20-100 K). The origin of the acceptorlike states within the forbidden gap was suggested to arise from dangling-bond-related defects, which could be partially removed by the prolonged annealing. Hall mobility (mu(H)) data in the temperature range from 20 to 300 K revealed th at the charge carriers were subjected to two kinds of scattering mechanisms . At low temperatures, ionized center scattering was found to dominate and mu(H) showed a T-alpha dependence, where alpha is a positive constant; whil e at higher temperatures mu(H) was found to vary as T-0.5 rather than the e xpected T-3/2 dependence. This was explained in terms of a structural-imper fection-limited mean free path of the charge carriers. [S0163-1829(98)06648 -X].