A POINT-CONTACT METHOD FOR DETERMINING THE CHARGE CARRIER DENSITY AND MOBILITY IN THIN SEMICONDUCTING LAYERS.
STANFORD UNIV CA STANFORD ELECTRONICS LABS
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The Hall four-point probe developed here consists of a square array of point contacts centered on a thin circular sample with a perpendicular magnetic field. It is useful for the quick and routine measurement of the resistivity and the Hall coefficient. This method is unique in that the Hall effect is measured using four contacts which do not lie on the edge of a sample. This problem is solved by a new theory, and the results is expressed in terms of resistivity and Hall correction factors. The potential measured by the Hall four-point probe is the product of the potential measured as if the contacts were on the sample edge which is van der Pauws method times a correction factor. Correction factors for the Hall four-point probe are verified experimentally using uniformly doped InAs and Ge. The new probe method was applied to the analysis of a planar Zn-diffused layer in n-type InAs. Removing incremental layers parallel to the surface, the charge carrier density and mobility were found as a function of depth through the diffused layer. This analysis, when compared to a radioactive-tracer analysis and chemical etch of a similarly diffused layer, revealed the following 1 in the p region at 77K the hole concentration is between 2 and 33 percent lower than the Zn concentration, 2 the pn to the minus power junction has a large irregularity of 20 microns, and 3 the diffusion tail extends five times deeper than the pn to the minus power junction and forms an abrupt n to the minus n power junction.
- Electricity and Magnetism
- Solid State Physics