Hopping conduction in uniaxially stressed Si:B near the insulator-metal transition

Journal Article · Thu Jul 01 04:00:00 EDT 1999 · Physical Review, B: Condensed Matter

DOI:https://doi.org/10.1103/PhysRevB.60.2286· OSTI ID:357609

Bogdanovich, S; Simonian, D; Kravchenko, S V; Sarachik, M P ^[1]; Bhatt, R N ^[2]

---

1. Physics Department, City College of the City University of New York, New York, New York 10031 (United States)
2. Department of Electrical Engineering, Princeton University, Princeton, New Jersey 08544-5263 (United States)

Using uniaxial stress to tune the critical density near that of the sample, we have studied in detail the low-temperature conductivity of p-type Si:B in the insulating phase very near the metal-insulator transition. For all values of temperature and stress, the conductivity collapses onto a single universal curve, {sigma}(S,T)=AT{sup 1/2}F[T{sup {asterisk}}(S)/T]. For large values of the argument, the scaling function F[T{sup {asterisk}}(S)/T] is well fit by exp[{minus}(T{sup {asterisk}}/T){sup 1/2}], the exponentially activated form associated with variable-range hopping when electron-electron interactions cause a soft Coulomb gap in the density of states at the Fermi energy. The temperature dependence of the prefactor, corresponding to the T dependence of the critical curve, has been determined reliably for this system, and is {proportional_to}T{sup 0.5}. We show explicitly that neglecting the prefactor leads to substantial errors in the determination of the T{sup {asterisk}}{close_quote}s and the critical exponents derived from them. The conductivity is not consistent with Mott variable-range hopping, exp[{minus}(T{sup {asterisk}}/T){sup 1/4}], in the critical region, nor does it obey this form for any range of the parameters. Instead, the conductivity of Si:B is well fit by {sigma}=AT{sup 1/2}&hthinsp;exp[{minus}(T{sup {asterisk}}/T){sup {alpha}}] for smaller argument of the scaling function, with {alpha}=0.31 related to the critical exponents of the system at the metal-insulator transition. {copyright} {ital 1999} {ital The American Physical Society}

• OSTI ID: 357609
• Journal Information: Physical Review, B: Condensed Matter, Journal Name: Physical Review, B: Condensed Matter Journal Issue: 4 Vol. 60; ISSN 0163-1829; ISSN PRBMDO
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
BORON
BORON ADDITIONS
DOPED MATERIALS
ELECTRIC CONDUCTIVITY
ELECTRON-ELECTRON INTERACTIONS
ENERGY GAP
FERMI LEVEL
SCALING
SILICON
STRESSES
TEMPERATURE DEPENDENCE