Ba. Aronzon et al., MANIFESTATION OF PERCOLATION CONDUCTIVITY OF SHORT-CHANNEL FIELD-EFFECT TRANSISTORS IN THE SPECTRUM OF SHALLOW INTERFACE STATES, Semiconductors, 31(12), 1997, pp. 1261-1267
The effective density of shallow interface states N-SS,, is investigat
ed in the temperature range T=77-300 K using the field-effect method i
n short-channel (0.5-5 mu m) Si-MNOS and GaAs-based FET's with high (g
reater than 10(12) cm(-2)) concentrations of built-in charge in the su
b-gate insulator. A peculiarity of the density of electronic states N-
SS,, was found having the form of a peak, which manifests itself more
distinctly at lower temperatures, higher concentrations of built-in ch
arge, and shorter gates. The peak was observed at the same values of t
he channel conductance G similar to q(2)/h, regardless of variations i
n the above-enumerated parameters, the thickness of the sub-gate insul
ator, and the channel-length-to-width ratio. This means that the energ
y depth of the peak (similar to 40-120 meV) varies in proportion to T,
which contradicts the current understanding of the interface states c
aused by both the fluctuation potential (FP) and surface defects or tr
aps. The results are interpreted within the framework of percolation t
heory applied to the conductivity of strongly disordered systems. The
N-SS,, peculiarity is associated with a transition from the conductivi
ty of a two-dimensional effective solid, which occurs when the fluctua
tion potential is strongly screened by surface electrons, to conductiv
ity via a quasi-one-dimensional potential trough organized by local re
gions with reduced surface potential under conditions of a strong fluc
tuation: potential. (C) 1997 American Institute of Physics. [S1063-782
6(97)01212-X].