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BYThe study of the piemresistance of n-Si arising at uniaxial elastic deformation along the [lll] direction (in absence of current carrier redistribution between individual valleys) due to the deformation-induced change of the effective mas8 is of special interest /1, 2/. X along the [lll] direction. In this case the dependences of the components of the effective mass tensor on X can be represented as follows:A s shown in /3/, the isoenergetic ellipsoids become three-axial for stress 2 where r= 6 . 7 4~1 0 -~ cm /kp.At 3 II f"_ila the isoenergetic ellipsoids of n-Si a r e oriented in such a way that the axis corresponding to m2 (for each ellipsoid) lies in the plane containing the deformation axis and the great ellipsoid axis.The conductivity teneor of one valley (in terms of their main axes) has the where mN = (mlm2m3)1/3, no is the Maxwellian equilibrium distribution function of electrons,' b~, a r e the components of the relaxation time tensor depending on the pressure X owing to ma = fm), ko is the Boltzmann constant, T is the absolute temperature.Since rX *I for the entire.pressure interval, then (2) may be decomposed:~~ 1) proepekt Nauki, 252028 Kiev, u88R.where OL and d, a r e the conductivity components of one valley in absence of mechanical stress calculated in /4/ and J is the combination of some angular integrals included in ~~( x ) .For the parameters of n-Si we obtain J = 0.87. Based on (3) we have where K = 4 /Ull is the anisotropy parameter.The experimental curve 1 in Fig. 1 even qualitatively differs from the calculated results (straight line 3 in Fig. 1) carried out by (4). In addition, (4) proved to be independent of temperature at least in the interval 78 to 300 K contradicting the experimental data (curves 1 and 2 in Fig. 1). However /l/, the temperature dependence of the piezoresistance measured in n-Si a t great 2 II [lll] was explained by supposing that the curvature of the dispersion &$(k) changes with removal of the energy degeneracy a t the Brillouin zone boundary (Fig. 1). This is equivalent to the occurrence of non-parabolicity which shall be taken into account below.Let u s suppose that the non-parabolicity has the Kane form The best agreement between theory and experiment (Fig. 1) is obtained at Lo = 2 . 0~1 0 . cm b e r g . ~n this case the non-parabolicity is insignificant since X E w h k T r . 2~1 0 -~ 4: 1. However, for great X the non-parabollcity essentially determines the behaviour and the temperature dependence of the piezoresistance.

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The magnetic field dependence of the magnetoresistance in nondegenerate n-Ge is experimentally and theoretically investigated. The conductivity component connected with the impurity scattering (uiY) is selected. Its magnetic field dependence in quantizing magnetic field is in accordance with theory.Es wird die Abhangigkeit des Magnetowiderstandes vom Magnetfeld fur nichtentartetes, n-leitendes Ge experimentell und theoretisch untersucht. Die mit Storstellenstreuung verkniipfte Leitfahigkeitskomponente (ubg) wird getrennt bestimmt. Ihre Abhkngigkeit vom Magnetfeld im quantisierenden Magnetfeld befindet sich in Ubereinstimmung mit der Theorie.

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