Khvyshchun M. Features of piezoresistance in unexposed and exposed to y -rays monocrystals of germanium and silicon.

The size of energy gap б(E) between the deep level (Ec-0,2)eB and the bottom of conductivity band has been found in the wide range of applied elastic mechanical stresses for the main crystallographic directions. It has been ascertained that for the explanation of the peculiarities of piezoresistance of germanium crystals in the field of their own conductivity it is necessary, besides deformational migration of charge carriers between the equivalent L-valleys and the change of the total concentration nj owing to the change of the energy gap width, to take into account the migration of charge carriers between L- and delta-valleys for the directions [111] and [100]. The value of energy gap б(E) change (at a rate of each 1000kG/cm2) between the deep level (Ec-0,17)eB) and the bottom of the conductivity band has been found for exposed to y-rays silicon monocrystals in wide range of applied elastic mechanicals stresses for direction [100] at T=125K. It is shown that at the presence of electrically passive impurity of germanium ( NGe=5*1018см?3) in silicon crystals with phosphorus concentration (NP=2*1016см?3 ) no ionization of electrically active impurity centers is observed at uniaxial elastic deformation. It became evident that energy levels of above mentioned centers have been already changed by existing crystalline deformation fields, formed as a result of covalent radii difference of germanium ( Rsi=1,17 A) and silicon ( Rge=1,22A) atoms. To obtain high accuracy at elastic moduli estimation for n-Si and n-Ge linear dependences lg(C*10?4)=f(X) were used. The offered method of n-Si and n-Ge elastic moduli value estimation is grounded on the use of data, obtained at the measurement of longitudinal piezoresistance Rox[111]=f(X) (for n-Ge) and Rox[100]=f(X) (for n-Si) only.