No abstract

AbsLracLThe CuFeEz ternary mmpound with a layered crystalline structure has teen ludied. nre mmpound Cr paramagnetic in lhc temperature range IO-ZM) K Invesligation of the p ( T ) temperature dependence demonstrates the fermn character of the carrier transpon with the Molt diffusional mechanism. ?he obtained power dependences n ( T ) , R ( T ) and o ( T ) allow us LO mnclude lhal CuFeTe belongs LO the gapless semiconductors. rile temperature behaviour of n(T), R ( T ) and o(T) can be explained by examining features from the electron spectrum of CuFeTez under mndilions where the characrer of the ~a n i e r

Studies of the influence of hydrostatic pressure up to 6500 kp/cm2 on the funda,mental absorption edge of eleven A2B4Cg-type compounds of chalcopyrite structure mere carried out at, room temperature. The large values of dE,/dP = (7.3 to 10.0) x eV kp-1 em2 were obtained for CdGeAs,, ZnSnAs,, ZnGeAs,, CdSnP,, CdSiAs,, ZnSnP,, CdGeP, (first group of crystals) and much smaller values -(--0.7 to +l.G) x eV kp-l cm, for ZnSiAs,, ZnGeP,, ZnSiP,, and CdSiP, (second group of crystals). The coniparison of these pressure coefficients with those of rl5-r1 and r15-X1 energy gaps in A3B5 compounds leads to t.he conclusion that the lowest conduction band minima in the first and second groups of X2B4C: crystals are rl and r, (or T, + TJ, respectively. This conclusion is in a good agreement with the calculated band structure of the investigated compounds and is confirmed by the studies of the slope of the fundamental absorption edge. The absorption edge of the first group of crystals is sharp due to the optical transitions I?, -+ rl (derived from lTI5 + rl in zincblende) and that of the second group of crystals is smooth and is caused by the transitions I?, -+ T3 or I ? , + T, + T, (both correspond to indirect transitions r15 -+ X, in zincblende).

No abstract

The temperature.dependences of the Hail coefficient R(T), specific conductivity a(T), and electron concentration n(TJ of CuFeS, and CuFeTe, monocrystals are investigated. From their power dependences the zero bandgap for the electron excitations of these substances is established. Analysis of the temperature dependence of the mobility p(7) enables u s to conclude that the conduction electrons are in t h e magnetopoiaron (ferron) state of large and small radius in CuFeS, and CuFeTq respectively. The existence of various power dependences R(T), u(5) and n(T) in CuFe.Al, -.& solid solutions, in the CuFeS, compound, which is under pressure, and in the CuFeTe, compound, is pointed out. These anomalies are explained both by the manifestation of peculiarities of the ferron spectrum and by various mechanisms of ferron mobility. It is pointed out that the theoretical group analysis of the CuFeS, structure corroborates the possibility of the existence of the zero-gap state at the P point of the Briliouin zone. Some peculiarities of the zero-gap spectra of the both substances are discussed.