Properties Of Narrow-gap Semiconductors Research Articles

Conductivity-limiting bipolar thermal conductivity in semiconductors.

Intriguing experimental results raised the question about the fundamental mechanisms governing the electron-hole coupling induced bipolar thermal conduction in semiconductors. Our combined theoretical analysis and experimental measurements show that in semiconductors bipolar thermal transport is in general a “conductivity-limiting” phenomenon, and it is thus controlled by the carrier mobility ratio and by the minority carrier partial electrical conductivity for the intrinsic and extrinsic cases, respectively. Our numerical method quantifies the role of electronic band structure and carrier scattering mechanisms. We have successfully demonstrated bipolar thermal conductivity reduction in doped semiconductors via electronic band structure modulation and/or preferential minority carrier scatterings. We expect this study to be beneficial to the current interests in optimizing thermoelectric properties of narrow gap semiconductors.

Mixed-valence states in narrow-gap IV-VI semiconductors with rare-earth ions

The mechanism of valence-state formation in the IV-VI alloys doped with rare-earth impurities is analyzed with respect to certain properties of narrow-gap semiconductors. The mean-field approximation in the slave-boson representation is used to account for the strong electron correlation at the impurity. The energy, width, and filling factor of the impurity level are calculated as a function of both the band gap and position of the chemical potential. We also calculate the temperature dependence of the magnetic susceptibility of an impurity. It is shown that mixing to coupled conduction- and valence-band states makes the properties of rare-earth dopants sensitive to the band gap and Fermi level in the narrow-gap semiconductor host.

Resonance CARS in Narrow Gap Semiconductors

Coherent anti-Stokes Raman scattering due to spin transitions of free carriers in narrow gap semiconductors is discussed. The basic results of the electrodynamic theory of optical four-wave mixing and of the quantum mechanical calculation of the third-order non-linear susceptibility χ(3) are briefly reported in the context of the particular properties of narrow gap semiconductors. The enhancement of the Raman-like resonances of χ(3) for photon energies close to the fundamental gap is demonstrated and interferences of Raman and one-photon interband transitions are discussed. Applications of the method to epitaxial films of narrow gap semiconductors and to quantum well structures are presented.

Resonance CARS in Narrow Gap Semiconductors

Coherent anti-Stokes Raman scattering due to spin transitions of free carriers in narrow gap semiconductors is discussed. The basic results of the electrodynamic theory of optical four-wave mixing and of the quantum mechanical calculation of the third-order non-linear susceptibility χ(3) are briefly reported in the context of the particular properties of narrow gap semiconductors. The enhancement of the Raman-like resonances of χ(3) for photon energies close to the fundamental gap is demonstrated and interferences of Raman and one-photon interband transitions are discussed. Applications of the method to epitaxial films of narrow gap semiconductors and to quantum well structures are presented.

Dynamical Nonlinearity and Bistability of Narrow Gap Semiconductors

AbstractA brief review is presented of new photo‐Hall studies of linear and nonlinear optical properties of narrow gap semiconductors with specific relevance to optical bistability. InSb is chosen as the prototype crystal for this work. The nonlinear refractive cross‐section (σ = Δn/ΔN) is determined to be −1.1 × 10−18 cm3 near 5 μm at 77K and −(2.3 ± 1) × 10−18 cm3 near 10 μm at 300 K. The two‐photon absorption coefficient is found to be β = 7 cm MW−1. The results are in good agreement with theoretical prediction.