N-type Silicon Inversion Layers Research Articles

Occurrence of Ground and Excited-State Impurity Bands in Silicon Inversion Layers: Electric Field Effects

AbstractWe investigate the effects of charged impurities in n-type Silicon inversion layers. We show the occurrence of ground and excited-state impurity bands as a function of electric field and concentration. Also the effects of disorder and for given impurity concentrations, the lowest excited band play an essential role in the optical and transport measurements. For high electric fields the impurity bands go to the ideally 2D separated bands.

High-field drift velocity of electrons in silicon inversion layers

The dependence of the drift velocity on electric field for electrons in n-type silicon inversion layers is determined from the d.c. drain-conductance measurement of polysilicon resistive-gate field-effect-transistors. Up to fields 1.5 × 10 4 V/cm this dependence is well approximated by an empirical relationship which satisfies Thornber's theory. The extrapolated saturation drift velocity, nearly independent of normal (or gate) electric fields up to 8 × 10 5 V/cm, is 6.0 × 10 6 cm/s. This value is used in a field-dependent model for electron mobility in silicon inversion layers implemented in a 2-D device simulator. Accurate numerical simulations of the resistive-gate device correctly predict the experimentally observed drain current-drain voltage characteristics.

Observation of valley splitting in (111) n-type silicon inversion layers : T. Englert, D. C. Tsui and G. Landweher Solid St. Commun. 33, 1167 (1980)

Observation of valley splitting in (111) n-type silicon inversion layers : T. Englert, D. C. Tsui and G. Landweher Solid St. Commun. 33, 1167 (1980)

Valley splitting in (001), (011) and (111) Si-MOSFETS

A unified theory of the (bare) valley splitting in (001), (011), and (111) n-type silicon inversion layers is given on the basis of symmetry breaking in conjunction with spin-orbit interaction. The group- and perturbation-theoretical discussions of the matrix elements relevant for valley splitting indicate that distortions of the Si lattice close to the silicon surface may be important to the considered splitting mechanism.

Electron-phonon interactions in n-type silicon inversion layers at low temperatures

Electron-phonon interactions in n-type silicon inversion layers at low temperatures

Hall conductivity in n-type silicon inversion layers under strong magnetic fields

Quantitative results of the Hall conductivity σ xy as well as the transverse conductivity σ xx in silicon MOS inversion layers have been obtained successfully by use of the Hall current method. Experimental electron mobility dependence of the Landau level width in higher Landau levels are in good agreement with theoretical predictions. The electron localization in strong magnetic fields has been investigated by utilizing σ xy as well as σ xx .

Electron-phonon interactions in n-type silicon inversion layers at low temperatures

Electron-phonon interactions in n-type silicon inversion layers at low temperatures

Lineshape analysis of Shubnikov-De Haas oscillations in (100) n-type silicon inversion layers

Lineshape analysis of Shubnikov-De Haas oscillations in (100) n-type silicon inversion layers

Hall conductivity in n-type silicon inversion layers under strong magnetic fields

Abstract Quantitative results of the Hall conductivity σ xy as well as the transverse conductivity σ xx in silicon MOS inversion layers have been obtained successfully by use of the Hall current method. Experimental electron mobility dependence of the Landau level width in higher Landau levels are in good agreement with theoretical predictions. The electron localization in strong magnetic fields has been investigated by utilizing σ xy as well as σ xx .

Observation of valley splitting in (lll) n-type silicon inversion layers

An additional splitting of Shubnikov-de Haas oscillations in (lll) n-type silicon inversion layers in observed. We attribute it to valley splitting, analogous to that previously observed on (100) surface layers, and point out that theoretical explanations of valley splitting, restricted to the valley configuration in (100) inversion layers, are not applicable.

Broken symmetry states in n-type silicon inversion layers

A detailed examination of the possible intervalley electron-electron interactions in n-type silicon inversion layers leads to a model Hamiltonian of considerably greater complexity than that studied by Kelly and Falicov. While the theory of broken-symmetry states retains its structure, significant new points of detail emerge. At zero stress at the Si(111)/SiO2 interface, all six valleys participate in the ground state; but quite small stresses suffice to destroy such a state, while at the Si(100)/SiO2 interface a broken-symmetry state at intermediate stress is rather easier to stabilise.

Analysis of ρ xx minima in surface quantum oscillations on (100) n-type silicon inversion layers

The analysis of resistance minima ρ xx min in surface quantum oscillations of n-type silicon inversion layers shows that for samples of high mobility ρ xx min depends on the energy gap in the density of states between the broadened Landau levels. For a constant magnetic field, the energy gap is determined by the level width, the Landé g-factor, and the valley splitting. From our analysis of the temperature dependence of ρ xx min and from measurements in a tilted magnetic Held, values for the level broadening and the g-factor could be deduced. For the first time experimental g-values were determined at Fermi energies where no enhancement due to many body effects is expected.

The dependence of the electronic ground-state of n-type silicon inversion layers on stress, temperature, magnetic field and gate voltage

The ground-state for n-type inversion layer electrons at the Si(100)/SiO 2 interface is studied theoretically as a function of temperature, uniaxial applied stress, magnetic field and gate voltage. We summarise trends among the results obtained from a model that includes charge-density-wave states, and present a unified interpretation of a whole series of experimental data that otherwise lead to divergent interpretations. Details of the calculations appear elsewhere in the literature. Experiments that test the theory and provide estimates of the electronic interactions are discussed.

Stress and temperature dependence of the electronic properties of n-type silicon inversion layers

The ground state for n-type silicon inversion electrons at the Si (100)/SiO2 interface is studied theoretically as a function of temperature, applied uniaxial stress and gate voltage. Calculations on a model that includes charge-density-wave states under favourable conditions provide results which allow a consistent and unified description of a whole series of experimental data that otherwise lead to divergent interpretations. One novel aspect of the theory is the ability of temperature and/or stress to induce and destroy a broken-symmetry ground state with a first- and a second-order phase transition. Parameters in the theory can, in principle, be used to estimate the effectiveness of screening in the inversion layer and the strength of electron-lattice coupling at the interface.

Mechanical stress influence on effective masses in Si inversion layers

Shubnikov-De Haas oscillations and Hall mobility have been measured under uniaxial stress for (100) and (110) n-type silicon inversion layers. For both cases no population effect into valleys with different masses could be seen. Intravalley mass increases up to 25% have been observed for uniaxial compression of P = 230 N/mm 2. Under stress the occupied degenerate valleys shift relative to each other and cause changes of the SdH amplitudes. For the (110) surface orientation a preexisting uniaxial stress in the surface plane has been detected.

Surface quantum oscillations in (110) and (111) n-type silicon inversion layers

Shubnikov-de Haas oscillations have been studied for (110) and (111) n-type silicon inversion layers. The measured cyclotron masses m c = (0.38 ± 0.03) m 0 and m c = (0.40 ± 0.03) m 0 for (110) and (111) planes, respectively, are larger than theoretically predicted values. The experimental valley degeneracy factor g v = 2 ± 0.2 for both orientations is also at variance with self consistent calculations. The electronic g-factor depends on the surface carrier concentration and is enhanced over its bulk value. There was no evidence for the occupation of other subbands.

Far Infrared Cyclotron Resonances in the Silicon Inversion Layer

Cyclotron resonances in n-type silicon inversion layers has been observed at 4.2 K at 45.407 and 32.12 cm-1. Both real and imaginary parts of the channel conductance are measured with a homodyne detector as the magnetic field is swept from 0 to 100 kG. In this way the resonant electron density, mass and scattering rate have been measured for electron densities between 0.38×1011 and 9.0×1012/cm2. The mass is essentially constant, (0.20±01) m0, and does not increase at low electron densities. The far-infrared mobility drops monotonically with increasing density in marked contrast to the dc mobility which exhibits a strong maximum in the range 1.5×1012/cm2. The resonant electron density is proportional to gate voltage over the entire range of concentrations. The results indicate that the decrease in dc mobility at low densities is not due to carrier freeze out or increase in the microscopic scattering rate but may be related to a break up of the channel.