Quasi-two Dimensional Structure Research Articles

Theory of Exchange Interaction Effects on Electronic States in Highly-Doped Low-Dimensional Structure Semiconductors

The previously developed theories of the impurity-doping effect on electronic states in quasi-two and quansi-one dimensional structure semiconcluctors are extended to take into account the Coulomb-hole term in the exchange interaction. The theory is applied to single-quantum-well and single-quantum-wire of n-type GaAs embedded in undoped GaAlAs, considering the conduction band. The effect of the Coulomb-hole term is to partially cancel the shift of the density of states (DOS) toward higher energy produced by the multi-site multiple impurity-scatterings. It is shown that the Coulomb-hole term effect in lower-dimension structures is as important as that in a three-dimensional structure.

Absorption Due to Quasi-Two-Dimensional Electronic Transition in Very Thin Films of PbI2

Absorption spectra in a very thin film of PbI 2 have been measured by using multiple total reflections at 90 K. A new band appearing at 21.14 kcm -1 is assumed to be associated with an exciton located in a few layers adjacent to vacuum, and the exciton binding energy of 650 ±50 cm -1 is larger than that of the bulk exciton. This larger binding energy suggests quasi-two dimensionality of this exciton. Moreover, a step and a plateau appear at 20.8 kcm -1 and in 22–23 kcm -1 , respectively. These structures are concluded to be due to the band-to-band transition in the quasi-two dimensional electronic structure.

Specific heat of the semiconducting layered compound SnSe 2 at low temperatures

The specific heat of the layer compound semiconductor tin diselenide SnSe 2 has been measured in the temperature range from 2.7 to 280 K. In this range, the overall temperature dependence of the specific heat is dominated by the lattice contribution, which yields a limiting Debye characteristic temperature at absolute zero θ D (0) = 140 ± 2K. The increase in the specific heat at low temperatures is more gradual than what would be expected for a simple Debye solid, and reflects the quasi-two dimensional layer structure of this compound.