CHARACTERIZATION OF THE ELECTRICAL-PROPERTIES OF SEMIMETALLIC BI FILMS BY ELECTRICAL-FIELD EFFECT

The electrical field effect (EFE) was used to investigate and to chara cterize the electrical properties of Bi films. The samples were prepar ed in a capacitor configuration with Al as the gate electrode, Al2O3 a s the dielectric and the thin (similar to 1300 Angstrom) thermal-evapo ration deposited Bi film sample serving as the other electrode. The de pendence of EFE on the electrical field (up to electrical displacement s similar to 10(7) V/cm or approximate to 10(13)[e]/cm(2) ''surface'' charge) and on temperature (15-300 K), and also the temperature depend ence of Hall constant, were determined. The experimental results are s hown to be consistent with the EFE theory of a semimetal film, assumin g: that: (1) the film has an interface ''dead layer'' (similar to 600 Angstrom) that does not contribute markedly to EFE due to its extremel y low carrier mobilities. Only in the rest, ''good'' part of the film, the electroconductivity is modulated and leads to a measurable EFE; ( 2) the temperature behavior of EFE follows the temperature dependence of the electron and hole mobilities and its sign is determined by thei r relative magnitudes. (C) 1997 American Institute of Physics.