Measurement of the Electron Drift Velocity in Silicon

Citation

Rodriguez, Valentin (1969) Measurement of the Electron Drift Velocity in Silicon. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/B8ER-9195. https://resolver.caltech.edu/CaltechETD:etd-09272002-164439

Abstract

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. The drift velocity of electrons in silicon at high electric fields is measured in the <111> direction over the range of lattice temperatures from 4.2[degrees]K to 300[degrees]K. This information is obtained from measurements of pure unipolar (sclc) space-charge-limited current. Structures of the type [n^+ n n^+] and [n^+ p n^+] have been manufactured to study this current. The experimental V-I characteristics obtained from these structures offer a consistent picture. The theoretical models adopted are simple and adequate. The drift velocity is found to increase monotonically with electric field strength in the range of lattice temperatures covered. It is established that a limiting drift velocity exists at high electric fields. Its temperature dependence is measured from 4.2[degrees]K to 300[degrees]K. No indication of a negative differential mobility - as observed in GaAs and Ge below 77[degrees]K - is present. At 300[degrees]K and 77[degrees]K the velocity-field relationship is determined from the linear (low field) range up to a field strength of the order of [10^5] volt/cm. A comparison with results obtained by other authors at those two temperatures yields good agreement, in particular at 300[degrees]K. A fairly complete treatment of the influence on unipolar sclc of: (1) trapping, (2) geometry, (3) ionized impurities, (4) illumination, and (5) thermal carriers, is presented. In particular, the effect of giant trapping and normal trapping is studied in detail. The threshold voltage is measured as a function of lattice temperature from 4.2[degrees]K to 300[degrees]K. In the range from 4.2[degrees]K to 50[degrees]K, its temperature dependence is correlated to that of the trapping crosssection for the compensated donor atoms. Above 77[degrees]K, the temperature dependence of the threshold voltage is linked to that of the Debye length. From this analysis, the degree of compensation of the material is derived in a simple way.

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