On the EBIC Contrast of Dislocations in Si

Abstract

EBIC contrast in correspondence of the etch‐pit rows from room temperature microhardness indentations and from polishing scratches are examined with and without successive mechanical and/or thermal treatments. According to the observations clean dislocations show no contrast, contaminated dislocations show contrast which may be treated by assuming suitable boundary conditions consistent with the existence of space charge cylinders around the dislocations. Contrast bands observed in correspondence of etch‐pit rows after suitable treatments are related to point defects introduced together with the dislocations. Relative contrast of screw and edge character dislocations is deduced from the different visibility of half‐loop arms.

Ebic contrast of defects in cadmium telluride. II. Theory

“…2) or in the bulk region alone when the contribution of the SCR becomes less important (second decrease in fig. 2); this latter case corresponds to the model of Donolato (1979). It could not be observed in our experiments owing to the lack of resolution beyond 30 kV, and to the impossibility of obtaining E , higher than 45 kV.…”

“…6). This does not happen when the SCR is negligible; effectively, as shown by Donolato (1979), the shape of the curve is not altered by a change in L and/or T,/z. Furthermore, the contrast increases with L. …”

“…Let us just write that I D , = -en.$ f (al, Az, zo, a2); I,, increases with Az, zo, and decreases when a1 and a2 increase. When a defect is located in the bulk region, the new carrier density Ap'(r) satisfies the modified continuity equation (Donolato 1978/79) where zD(r) is the reduced lifetime of holes inside V, . It will be taken as constant.…”

“…The experimental values of the contrast are typically 5-10% and are simulated by taking E~ equal to about 50nm. The cylinder of radius c0 could therefore be assimilated to the space-charge cylinder around the dislocation line, E~ being the screening or Debye-Hiickel length 1 , (Castellani, Gondi, Patuelli and Berti 1982); it depends on the carrier concentration no as…”

“…Theories of EBIC contrast of dislocations, based on solutions of the continuity equation, have been developed for dislocations located in the bulk region adjacent to a Schottky diode (Donolato 1979, Donolato andKlann 1980) or a pn junction (Pasemann 1981, Donolato 1981. It has been shown in Part I (Sieber and Philibert 1987) that these earlier theories cannot explain the behaviour of the EBIC contrast as a function of the accelerating voltage E , for dislocations in n-type CdTe.…”