Subband Splitting Research Articles

Effect of subband splitting on Si inversion layers

Abstract The subband structure of (100)Si inversion layers can be altered by either uniaxial stress or substrate bias due to deformation potential and quantizing surface field, respectively. The reduced splitting between E0 and E0 caused by compressive stress is shown to be exactly compensated by the additional surface field via substrate bias at high compressive stress. At low compressive stress (≲ 109 dyn cm−2) and low carrier concentration (

Substrate bias effects on subband separation and interband scattering in Si (110) p-channel mosfets

Light and heavy hole subband splitting as a function of substrate bias is characterized and found to increase with increasing depletion charge. Oscillatory interband scattering is reported.

D—s, p Resonance and Electronic Structure of Compounds, Alloys, and Solid Solutions

AbstractOn the basis of the valence band structure regularities, obtained from combined X‐ray spectral and X‐ray photoelectron studies of electron energy spectra, a model is suggested for the interaction between valence electrons of s, p‐elements and d‐electrons of IIIA, IIB, IB, and transition metals under the formation of compounds, alloys, and solid solutions, the so called d—s, p resonance. The model qualitatively explains different observed manifestations of state interaction: the energy displacements, subband splitting, mixing of states of different symmetry or, vice versa, pushing of s, p‐states out of the energy interval, occupied by d‐band, due to the mutual energy arrangement of d‐ and s, p‐subbands.

Electronic properties of the two-dimensional system at GaAs/Al xGa 1−xAs interfaces

Abstract At the interface of GaAs/n-AlxGa1−xAs heterostructures charge carriers are transferred from the donors in AlxGa1−xAs into the conduction band of GaAs where they form a quasi-two-dimensional electron layer. The carrier confinement at the interface is demonstrated by Shubnikov-De Haas measurements. Resonant inelastic light scattering from the two-dimensional electron gas is a direct measure of the subband splitting in the space charge layer. The results are compared with recent self-consistent calculations.

Electronic properties of the two-dimensional system at GaAs/Al xGa 1− xAs interfaces

At the interface of GaAs/n-Al x Ga 1− x As heterostructures charge carriers are transferred from the donors in Al x Ga 1− x As into the conduction band of GaAs where they form a quasi-two-dimensional electron layer. The carrier confinement at the interface is demonstrated by Shubnikov-De Haas measurements. Resonant inelastic light scattering from the two-dimensional electron gas is a direct measure of the subband splitting in the space charge layer. The results are compared with recent self-consistent calculations.

Subband spectroscopy by surface channel tunneling

Surface channel tunnel junctions (SCTJ) can be fabricated by replacing the usual degenerate n-type source contact on a weakly p-type substrate by a highly degenerate p-type source. In the presence of a gate voltage strong enough to produce a surface inversion layer, a tunnel junction connecting the three-dimensional p + source and the quasi-two-dimensional n-type surface channel can occur. The I- V characteristics of this SCTJ will yield valuable information about the subband splittings and other electronic properties of the surface inversion layer.

Hartree calculations for n-inversion layers on stressed silicon surfaces

The energy splittings and occupation number densities in n-type inversion layers are estimated in a Hartree calculation with a parametrized exponential potential. Good agreement with experiment is obtained for low temperatures and for electron concentrations 1×10 12cm −2 ⩽ N s ⩽1×10 13 cm −2. On the basis of these calculations the influence of uniaxial stress is considered. For a 001-stress along a (100)-surface one finds that (i) the stress induced subband splitting is a function of the electron density, and (ii) the splitting E 1- E 0 within a subband system depends on the applied stress.

Intersubband spectroscopy by photoconductivity and absorption in inversion layers onp−Si(100)

Subband spectroscopy in an inversion layer on $p\ensuremath{-}\mathrm{Si}(100)$ is done simultaneously in photoconductivity and absorption. The resonances observed are investigated in their dependence on inversion electron density ${N}_{s}$ and depletion charge ${N}_{\mathrm{dep}}$ and are interpreted as transitions from the ground subband to higher subbands of the two valleys with heavy mass perpendicular to the surface. Absorption and photoconductivity give identical resonance positions and similar lineshape. The dependence of the subband splitting on ${N}_{s}$ and ${N}_{\mathrm{dep}}$ is found to agree with the measurements of Kneschaurek et al. and the most recent theory by Ando. Agreement with the photoconductivity results of Wheeler and Goldberg and the hot-electron-induced emission experiment of Gornik and Tsui can only be achieved if the latter results are assumed to correspond to a much lower ${N}_{\mathrm{dep}}$ than derived from the substrate resistivity at 300 K. In contrast to the results of Wheeler and Goldberg the amplitude of the photoconductivity signal exhibits a strong temperature dependence between 1.7 and 6 K.

On the absorption of infrared radiation by electrons in semiconductor inversion layers

Resonances in the inversion layer for infrared fields normal to the interface do not occur at the electric subband splittings. They are shifted from the subband splittings by resonant screening of the infrared field. The corrections for (100) Si surfaces are shown to be comparable to the shifts ascribed to many-body effects.

Influence of intervalley transitions on the photoconductivity in n-type Si 〈100〉 inversion layers

Transitions between the different sub-band systems corresponding to the valleys with low and high effective mass in the direction of surface quantization involve large momentum transfer. As a consequence the probabilities for impurity induced transitions between the respective sub-band systems are low. The corresponding transitions by phonon emission are energetically forbidden if the sub-band splitting does not exceed the energy of acoustic phonons near the K-point. Negative photoconductivity due to carrier transfer into the sub-band system with lower mobility and extremely long response times, as observed experimentally, 1 results if the sub-band splitting is less than this energy. Photoconductivity effects in 〈100〉 inversion layers will be weaker and response times will be much shorter for sub-band splitting larger than the critical value. For the corresponding case in 〈100〉 inversion layers, in contrast, strongly enhanced photoresponse is expected and the long response time should persist.

Calculated Energy Levels and Optical Absorption inn-Type Si Accumulation Layers at Low Temperature

Self-consistent sub-band splittings and inter-sub-band optical matrix elements are calculated for $n$-type accumulation layers at temperatures low enough that the bulk carriers are frozen out. The energy splittings are sensitive to the concentration of acceptor impurities in the surface space-charge layer.