A. Ghoshal

On the effective electron mass in quantum well wires of ternary chalcopyrite semiconductors

SummaryAn attempt is made to study effective electron mass in quantum well wires of ternary chalcopyrite semiconductors by formulating a new 1D dispersion relation, within the framework of thek·p formalism considering the anisotropies in the band parameters. It is found, taking quantum well wires ofn-CdGeAs2 as an example, that the effective Fermi level mass depends on the subband index due to the combined influence of crystal-field splitting parameter and the anisotropic spinorbit splitting parameters, respectively. The masses increase with increasing carrier degeneracy and decreasing film thickness, respectively. In addition, the well-known results for the corresponding parabolic energy bands have been derived as special cases of the generalized formulations.

On the thermoelectric power in quantum well of A3IIB2V semiconductors in the presence of a classically large magnetic field

SummaryAn attempt is made to study the thermoelectric power of the carriers in quantum well of A3IIB2V semiconductors, taking Cd3As2 quantum well as an example. It is found, on the basis of newly derived 2DE−ks dispersion relation by including various types of anisotropies in the energy spectrum that the thermoelectric power decreases with increasing electron concentration and decreasing film thickness respectively. In addition, the corresponding well-known results for bulk specimens of isotropic parabolic energy bands are also obtained from the expressions derived.

Influence of magnetic quantization on the effective electron mass in Kane-type semiconductors

SummaryWe study the effective electron mass at the Fermi level in Kane-type semiconductors on the basis of fourth order in effective mass theory and taking into account the interactions of the conduction electrons, heavy holes, light holes and split-off holes, respectively. The results obtained are then compared to those derived on the basis of the well-known three-band Kane model. It is found, takingn-Hg1−xCdxTe as an example, that the effective electron mass at the Fermi level in accordance with fourth-order model depends on the Fermi energy, magnetic quantum number and the electron spin respectively due to the influence of band nonparabolicity only. The dependence of effective mass on electron spin is due to spin-orbit splitting parameter of the valence band in three-band Kane model and the Fermi energy due to band nonparabolicity in two-band Kane model. The same mass exhibits an oscillatory magnetic-field dependence for all the band models as expected since the origin of oscillations in the effective mass in nonparabolic compounds is the same as that of the Shubnikov-de Hass oscillations. In addition, the corresponding results for parabolic energy bands have been obtained from the generalized expressions under certain limiting conditions.

Influence of Quantization of Band States on the Effective Electron Mass in Quaternary Alloys.

SummaryAn attempt is made to study the effective electron mass in quaternary alloys, taking a In1−xGaxAsyP1−y lattice matched to InP, by using the three-band Kane model under different physical conditions,e.g. bulk specimens, magnetic quantization, cross-field configuration, quantum well, electric-field-aided quantum well, magnetic-field-aided quantum well, quantum well under cross fields, quantum well wires, electric-field-aided quantum well wires, magnetic-field-aided quantum well wires and quantum well wires under cross fields by formulating the respective expressions. We have plotted the effective Fermi level mass with various physical variables under different conditions. In the presence of a quantizing magnetic field the effective mass depends on the spin splitting of Landau levels due to the spin-orbit splitting parameter of the valence bands. Under cross-field configuration and the various quantum confined low-dimensional systems, the effective masses depend on the respective quantum numbers in addition to the Fermi energies even for parabolic models because of the inherent features of such systems. In addition, the corresponding results for relatively wide-gap materials have also been obtained from our generalized formulations under certain limiting conditions.

A simple analysis of the einstein relation in bismuth under different physical conditions

SummaryWe have studied the Einstein relation of the diffusivity-mobility ratio of the carriers in Bi in accordance with the McClure and Choi, the hybrid, the Cohen, the Lax and the ellipsoidal parabolic energy band models under magnetic quantization, cross-field configuration, quantum wells, electric-field-aided quantum wells, quantum wells under cross-field configuration, quantumwell wires, electrifield-aided quantum well wires and quantum well wires under cross-field configurations, respectively. The Einstein relation varies with various physical variables in different manners which are totally band structure dependent. We have also suggested an experimental method of determining the diffusivity-to-mobility ratio in degenerate materials having arbitrary dispersion laws.

Photoemission from quantum-confined structure of nonlinear optical materials

Photoemission from quantum wells, inversion layers, quantum well wires, and quantum dots of nonlinear optical materials has been studied using n-CdGeAs2 as an example. Photoemission was formulated by deducing the dispersion law within the framework of the k-p formalism taking into account all types of anisotropies of the energy band parameters. Photoemission is found to increase with incident photon energy in a ladderlike manner and to exhibit an oscillatory dependence on changing film thickness, surface fields at both high and weak electric field limits, and the carrier density. It is concluded that the numerical values of the photoemission are the greatest in quantum dots and the smallest in bulk specimens.

Influence of photon energy on the photoemission from nonlinear optical materials and devices under different physical conditions

An Attempt is made to study the photo-emission from bulk specimen, inversion layer, quantum wells, quantum wires (QWs) and quantum dots (QDs) of non-linear optical materials by using the generalized electron energy spectrum and taking n-CdGeAs2 as an example. We have also studied these same dependences in II2 - VI (CdS/CdTe) and HgTe/CdTe superlattices (SLs) under magnetic quantization. It is found that in all the cases the photo-emission exhibits ladder-like dependences with increasing photon energy. The photo-emission is greatest for HgTe/CdTe SL and laest for bulk n-CdGeAs2

Generalized Raman gain in nonparabolic semiconductors under strong magnetic field

This paper investigates the quantum oscillations of the Raman gain in non-parabolic semiconductors under strong magnetic quantization, taking A3II B2V compounds as examples of nonlinear optical materials. The magneto-dispersion law was formulated in the said material within the framework of k. p formalism taking all types of anisotropies of the energy spectrum. The expression for the Raman gain for the said compound was derived, taking Cd3P2 as an example by including spin and broadening effects. It is found that the Raman gain increases with increasing electron concentration and oscillates with magnetic fields. The numerical values of the gain are greatest for the proposed dispersion relation of A3II B2V type of nonlinear optical materials as compared to wide gap model and the theoretical analysis is in agreement with the experimental observations as reported elsewhere. In addition, the corresponding results for three-band Kane model, two-band Kane model, and parabolic energy bands also have been formulated.

On the field emission from superlattices of small-gap materials with graded structures in the presence of a strong magnetic field

The field emission from III-V, II-VI, PbTe/PbSnTe, strained layer, and HgTe/CdTe superlattices with graded structures under magnetic quantization is investigated and compared with that of the bulk specimens of the constituent materials. The doping and magnetic-field dependences of the magneto-field emission of these superlattices are analyzed, and it is found that the field emission exhibits oscillatory dependences on the inverse magnetic field and electron concentration with more significant oscillations appearing in the HgTe/CdTe superlattices. Relations for the bulk specimens are obtained from the special cases of generalized formulations.

Diffusion coefficient of the minority carriers in quantum-confined lasers

of the electrons among tne size quantized levels. It may benoted that the quantum wire lasers produce very large changes in thediffusion constant. In quantum wire lasers, only one free directionof motion is allowed for the charge carriers. cbnsequently, thecrossing of the Fermi level by the size quantized subbands would havemuch greater impact on the redistribttion of the electrons among theallowed levels, as compared to found for quantum well lasers. Thediffusion