Chau-Jy Lin

Hall effect in bismuth in quantizing magnetic fields

The Hall effect has been investigated in the very low-temperature limit in bismuth, when the lattice scattering is dominant in solids. The energy band structure of bismuth carriers is assumed to follow the modified nonellipsoidal, nonparabolic (MNENP) model. Results show that the Hall coefficient and Hall angle oscillate with the dc magnetic field, and the period and amplitude of the oscillations increase with the dc magnetic field. We also compare our numerical results with those found using other types of energy bands.

Free‐carrier absorption in n‐type gallium arsenide films for polar optical phonon scattering

The free‐carrier absorption in n‐type GaAs films has been investigated for quantum well structures fabricated from III–V semiconducting materials where polar optical phonon scattering is predominant. Attention is given mainly to the case where the electromagnetic radiation is polarized in the layer plane, and the processes involving both emission and absorption of polar optical phonons. The energy band of electrons in semiconductors is assumed to be nonparabolic. Results are shown that the free‐carrier absorption coefficient in n‐type GaAs films depends upon the photon frequency, the width of the quantum wells, and temperature. However, in the small quantum well region such as the width of quantum wells d<30 A, the free‐carrier absorption coefficient will be independent of temperature. Moreover, the free‐carrier absorption coefficient oscillates with the width of quantum wells for larger quantum wells.

Free-carrier absorption in n-type piezoelectric semiconductor films

Free-carrier absorption in n-type GaAs films has been investigated for the case where the free carriers are confined in a quasi-two-dimensional semiconducting structure with a non-parabolic energy band of electrons. It is assumed that the carriers in semiconductors are scattered by acoustic phonons via firstly the deformation-potential coupling and secondly the piezoelectric coupling. Results show that the free-carrier absorption coefficient depends upon the polarization of the electromagnetic radiation relative to the direction normal to the quasi-two-dimensional structure, the film thickness, the photon frequency and the temperature of the semiconductors. The free-carrier absorption coefficient could be complex owing to the interaction of photons, phonons and conduction electrons in piezoelectric semiconductors. Firstly, when the deformation-potential coupling is dominant, the absorption coefficient increases with decreasing photon frequency and increasing temperature for the radiation field polarized parallel and perpendicular to the layer plane. It is also shown that the absorption coefficient increases with decreasing film thickness. Secondly, when the piezoelectric scattering is dominant, the absorption coefficient increases with decreasing photon frequency and decreasing film thickness for the radiation field polarized parallel and perpendicular to the layer plane. However, the absorption coefficient increases with increasing temperature for the radiation field polarized parallel to the layer plane while, for the radiation field polarized perpendicular to the layer plane, the absorption coefficient increases with decreasing temperature.

Hall effect of nonparabolicity in a nondegenerate indium antimonide

The Hall effect and transverse magnetoresistance in an intrinsic nondegenerate InSb have been investigated when the acoustic phonon scattering is the dominant scattering process. The energy‐band structure is assumed to be nonparabolic. Results show that Hall angle, Hall coefficient, and transverse magnetoresistance depend strongly on the dc magnetic field because of the energy‐dependent relaxation time. We have also studied the temperature dependence of the Hall effect and transverse magnetoresistance in an intrinsic nondegenerate InSb. The results show that the Hall coefficient is greatly enhanced in low temperatures, whereas the Hall angle changes very slowly with temperature.

Effect of phonon scattering on free-carrier absorption in n-type indium antimonide films

The free-carrier absorption in n-type InSb films has been investigated for carriers confined in quasi-two-dimensional (2D) semiconductors with the nonparabolic energy band of electrons. We discuss the effect of phonon scattering on the free-carrier absorption coefficient (~) for both deformation-potential coupling and piezoelectric coupling. ~ is found to depend on the photon polarization relative to the direction normal to the quasi-2D structure, the photon frequency, the film thickness, and the temperature. ~ could be complex due to the interaction between photons, phonons, and electrons. (i) When the acoustic phonon scattering is dominant, ~ increases with decreasing the film thickness for phonons polarized parallel or perpendicular to the layer plane. It is also shown that ~t increases with decreasing photon frequency and increasing temperature for photons polarized parallel to the layer plane, while for photons polarized perpendicular to the layer plane the ct temperature-dependence is more complicated. (ii) If the piezoelectric scattering is dominant, ~ is also decreasing with increasing the film thickness for photons polarized parallel or perpendicular to the layer plane. But ct decreases with increasing temperature for photons polarized perpendicular to the layer plane. Moreover, numerical results for the parallel polarization are much smaller than those for the perpendicular polarization.

Energy bands and electron density in bismuth with a uniform dc magnetic field

Using time-independent perturbation theory, we solve the energy eigenvalue equation for a free-electron gas in bismuth with the McClure-Choi modified nonellipsoidal nonparabolic (MNENP) model in the presence of a uniform dc magnetic fieldB. We investigate the effect of the dc magnetic field on the electron density at very low temperatures and compare the numerical results for this new band model with those for the Cohen nonellipsoidal nonparabolic (NENP), Lax ellipsoidal nonparabolic (ENP), and ellipsoidal parabolic (EP) models. The results show that the quantum oscillations of the electron density for the MNENP model show up much more notably than in the NENP, ENP, and EP models. The MNENP model seems better suited than the other models for describing physical phenomena associated with the magnetic field effect in bismuth at very low temperatures.

Impurity-limited mobility of semiconducting thin wires in n-type gallium arsenide

The impurity-limited mobility of semiconducting thin wires for the nonparabolic band structure of electrons in n-type gallium arsenide has been investigated by scattering from ionized impurities or from the uniform distribution of remote impurities. Results are shown that the impurity-limited mobility due to scattering from background impurities increases monotonically and slowly with increasing temperature, while the impurity-limited mobility due to scattering from remote impurities increases rapidly with temperature. It is also shown that the mobility for both types of impurities decreases with increasing wire radius. However, for scattering from remote impurities, the mobility appears slowly decreasing with the wire radius at higher temperatures.

Effect of nonparabolicity on free‐carrier absorption in semiconductors at quantizing magnetic fields

Effect of the nonparabolicity on free‐carrier absorption in nondegenerate semiconductors has been investigated at quantizing magnetic fields. The dominant scattering mechanism for electrons is assumed to be of the acoustic phonon scattering via the deformation‐potential coupling. When the radiation is polarized parallel to a magnetic field, the absorption coefficient oscillates with the magnetic field in lower fields and then increases monotonically with the field. These oscillations of the abosrption coefficient with the magnetic field will be diminished with decreasing temperature and depend on the band gap of semiconductors.

Effect of electron-phonon scattering mechanisms on free-carrier absorption in quasi-one-dimensional structures

Abstract The free-carrier absorption in ultrathin wires fabricated from III–V semiconductors such as n-type InSb has been investigated for the case where the electrons are scattered either by polar optical phonons or acoustic phonons. We study the interaction of longitudinal polar optical phonons with electrons and have neglected the interaction between electrons and transverse optical phonons in solids. The energy band of electrons in semiconductors is assumed to be nonparabolic. The scattering mechanisms of the interaction between electrons and phonons we consider here come from (a) electron-polar–optical-phonon scattering, (b) electron–acoustic–phonon scattering, and (c) piezoelectric scattering in semiconductors. Results are shown that the free-carrier absorption coefficient for the deformation-potential coupling is much larger than that for the piezoelectric coupling. It is also shown that the free-carrier absorption coefficient for the electron-polar–optical-phonon scattering is smaller than that for the electron–acoustic–phonon scattering. However, the free-carrier absorption coefficient increases quite slowly with the photon frequency for the electron–acoustic–phonon scattering. This is not the same result as that for the quasi-two-dimensional semiconducting structures.

Free‐carrier absorption of nondegenerate semiconductors in quantizing magnetic fields: Nonpolar optical phonon scattering

The effect of nonpolar optical phononscattering on the free‐carrier absorption in n‐type semiconductors such as germanium has been investigated quantum mechanically in quantizing magnetic fields. It is assumed that the energy band structure of electrons in semiconductors is nonparabolic and the dominant scattering mechanism for conduction electrons is of the nonpolar optical phononscattering. When the radiation is polarized parallel to a dc magnetic fieldB, the absorption coefficient appears to be of a complex value due to the interaction between the radiation field and the optical phonon field in nondegenerate semiconductors. Results show that the real part of the absorption coefficient oscillates with the magnetic field in the high‐field region, and imaginary part of the absorption coefficient appears with a few extremum points (peaks and dips) in high magnetic fields. These are different from those of the acoustic phononscattering in III–V compound semiconductors such as InSb or GaAs, in which the absorption coefficient oscillates with the magnetic field in lower magnetic fields and then increases monotonically with the field.