Strain-Induced MI Transition in n-Si and n-Ge: Physical Mechanisms and Transport Phenomena

Abstract

The analysis of experimental data on the pressure and temperature dependences of conductivity, the current-voltage characteristics (IVC), and the pressure dependence of the activation energy in n-Si and n-Ge crystals in the region of strain-induced metal-insulator transition (MIT) is presented. A remarkable change of the effective mass of carriers in semiconductors caused by straininduced transformation of the energy band structure is the main necessary condition for realization of this kind of metal-nonmetal transition.

Correlated increase of ε2‐ and ε1‐conductivity energies under strain‐induced metal–insulator transition in n‐Ge(Sb)

“…Since the L 1 -∆ 1 inversion causes the increase of the both components of electron effective mass ( * l m and * t m ), the strain-induced MI transition in n-Ge(Sb) was realized in the donor concentration range which remarkably exceeds the value of the critical concentration. The data obtained confirm the suggested mechanisms for the explanation of the strain-induced MI transition effect [9] in highly-doped monocrystalline n-Ge and the validity of the effective mass-donor conception for description of the Mott transition phenomenon. The strain-induced change of the metallic-type conductivity by the activation-type one takes place in the impurity band of germanium crystals heavily doped by shallow donors and, as a consequence, appearance and following increase of the ε 2 -conductivity energy occurs.…”

“…1, curve 1, temperature range 4.2 -20 K) because the antimony concentration exceeds essentially the respective critical concentration of this impurity in germanium: N(Sb)/N c (Sb) ≈ 3.7. Under [100] oriented uniaxial pressure a remarkably increasing of the electron effective mass takes place in the pressure range X > 2.1 GPa as a consequence of the L 1 -∆ 1 inversion of the conduction band minima type [9]. This effect is most advantageous for realization and examination of the strain-tuned MI transition in comparison with the effect of mixing of the ground state of shallow donor with the more extended valley-orbit split excited states in uniaxially strained multi-valley semiconductors [3,4].…”

“…N Sb = 5.3 × 10 23 m -3 .with the effective mass conception and the Mott criteria for the MI transition in solids ( = increase of the electron effective mass must lead to the corresponding increase of the MI transition critical concentration. Since the critical concentration of MI transition n c and electron effective mass m* is connected by the relationship[9]…”

Кремнієві р-МОН та n-МОН транзистори з одновісно деформованими каналами у нанотехнології електронних приладів

“…де n -концентрацiя домiшок виродженого напiвпровiдника, n c (X) -критична концентрацiя переходу метал-неметал, яка залежить вiд одновiсного тиску та може бути наведена у виглядi [6]:…”