K. K. Ghosh

Effect of size quantization on the Einstein relation in ultrathin films of non-parabolic semiconductors

An attempt is made to investigate the effect of size quantization on the diffusivity-mobility ratio of the carriers in ultrathin films of semiconductors having Kane-type nonparabolic energy bands. It is shown, takingn-type InSb as an example, that the ratio oscillates both with increasing film thickness and with increasing carrier concentration under degenerate conditions and remains unaffected otherwise. The corresponding results for parabolic semiconductors are also obtained from the expressions derived.

Effect of size quantization on the effective mass in ultrathin films ofn-Cd3As2

An attempt is made to investigate the effects of size quantization on the effective mass in ultrathin films ofn-Cd3As2. It is found that the effective mass at the Fermi level depends on the size quantum number due to the effect of crystal-field splitting, resulting in different effective masses at the Fermi level corresponding to different electric subbands. It is also observed that the different effective masses closely approach each other, for a given film thickness, with increasing electron concentration and, for a given electron concentration, with increasing film thickness.

Effect of size quantization on the effective electron mass in nonparabolic semiconductors

In recent years, with remarkable developments in MBE techniques, considerable work bas been done on the effects of size quantization in ultrathin films and multilayer heterostructures of semiconductors [1-6] . The quantum size effect (QSE), which becomes operative when the layer or the film dimension is comparable to the De Broglie wavelength of the carriers, produces changes in the microscopic properties of the same due to quantization of confined carrier motion. The restriction of the Carrier motion in the direction normal to the film or the layer (say, the z-direction) may be viewed as carrier eonfinement in a one-dimensional potential well leading to quantization of energy of the carriers in the z-direction which produces a discrete energy spectrum and a density-of-states function that is step-like in energy. Though many new effects associated with size quantization have already been reported in the literature [1 -6 ] , there still remain gaps in the investigations ruade on the effects of size quantization of the various physical features of ultrathin films and layers of semiconductors. For example, since the effective mass of the carriers in nonparabolic semiconductors is energy dependent [7], it is expected that the effective mass in thin films or layers of such semiconductors will be significantly influenced by the quantum size effect. In what 9 we shall demonstrate this by considering the effective electron mass in ultrathin films of Kane-type semiconductors [8], taking n-type InSb as an example. To be more specific, we shall consider only the effective mass at the Fermi level since InSb is a highly degenerate semiconductor particularly at low temperatures at which the observation of the quantum size effect becomes very convenient. In Kane-type semiconductors [8] like InSb having nonparabolic energy bands where A ~ E o and m, < m0, the E k dispersion relation tan be expressed [9] as

Effect of carrier degeneracy on the diffusivity-mobility ratio in n-Cd3As2

An attempt is made to study the dependence of the diffusivity-mobility ratio on carrier concentration in degenerate n-Cd3As2 according to the Bodnar model which has recently been shown in the literature from studies on magnetic quantization to be the most valid model for Cd3As2. The results obtained are then compared with those derived on the basis of the Kane model to indicate the amount of error that would be involved with the use of the same model since many authors have continued to use it for Cd3As2.