Abstract
We investigated unusual low temperature transport properties of InSb single crystals doped with manganese to concentrations in the range of 1017<NMn<2*1017cm-3 which includes the critical concentration for metal-insulator transition Ncr= 2*1017cm-3. It was found that in the temperature range T=10÷1.5K the resisitivity had an unusual behavior described by an exponential quadratic function ρ ∼ exp(Δ1/kT)2 where Δ1 varied from Δ1=0.3meV to Δ1=0. Coexistence of electrons and holes at temperatures around the metal-insulator transition in p-InSb(Mn) crystals gives the ground to explain the unusual temperature - resistivity dependence in the framework of excitonic insulator phase model (L. V. Keldysh and Yu. V. Kopaev, Sov. Phys. Solid State 6, 2219 (1965)).
Highlights
One of the fundamental properties of doped semiconductors is that their resistivity-temperature dependence at low temperatures obeys the law of variable range hopping conductivity (VRHconductivity).[1,2] On the insulator side of metal-insulator transition (MIT) VRH conductivity type was observed experimentally in n-Ge(Sb) [Ref. 3] and other doped semiconductors.[4]
Later[6,7] it has been shown that the temperature - resistivity dependence observed in the temperature range 10÷1,5K can be described by an exponential quadratic function ρ = ρ01 ex p( 1/kT )[2] (2)
The resistivity-temperature dependence was studied at temperatures of T=280-0,3K on several p-InSb(Mn) samples with manganese concentration in the range NMn =1÷3 ×1017cm-3 that covered the MIT critical concentration (Ncr=2*1017cm-3)
Summary
One of the fundamental properties of doped semiconductors is that their resistivity-temperature dependence at low temperatures obeys the law of variable range hopping conductivity (VRHconductivity).[1,2] On the insulator side of metal-insulator transition (MIT) VRH conductivity type was observed experimentally in n-Ge(Sb) [Ref. 3] and other doped semiconductors.[4]. Our studies of manganese-doped InSb crystals in a narrow range of manganese concentrations on the insulator side of MIT revealed[5] that p-InSb(Mn) can display an unusual temperature resistivity dependence, which cannot be explained in the framework of the VRH model. Later[6,7] it has been shown that the temperature - resistivity dependence observed in the temperature range 10÷1,5K can be described by an exponential quadratic function ρ = ρ01 ex p( 1/kT )[2 ] (2). The aim of this work is to study the influence of manganese concentration on resistivity and activation energy 1. We obtained data on charge carriers at low temperatures in p-InSb(Mn) crystals around Ncr and the results of resistivity, magnetoresistivity and Hall effect measurements at temperatures T=280-0,3K and magnetic fields B=0-10T
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