In the framework of effective-mass envelope-function theory, the optical transitions of InAs/GaAs strained coupled quantum dots grown on GaAs (100) oriented substrates are studied. At the Γ point, the electron and hole energy levels, the distribution of electron and hole wave functions along the growth and parallel directions, the optical transition-matrix elements, the exciton states, and absorption spectra are calculated. In calculations, the effects due to the different effective masses of electrons and holes in different materials are included. Our theoretical results are in good agreement with the available experimental data. © 1996 The American Physical Society.

Li Shu-Shen;Xia Jian-Bai;Yuan Z.;Xu Z.;Ge Weikun;Wang Xiang Rong;Wang Y.;Wang J.;Chang L.

Physical Review B Condensed Matter and Materials Physics

1996

Silicon tips used as field emitters have dimensions that are within the quantum confinement regime. Therefore they can be considered as freestanding silicon tips. In this letter, a photoluminescence spectrum of a 100× 1000 array of silicon tips was taken at 10 K. Narrow ultraviolet luminescence peaks were observed. Using the empirical pseudopotential homojunction model, it is demonstrated that these luminescence peaks come from energy levels arising from quantum confinement. By fitting the theoretical result to the experimental result, we conclude that the luminescence peaks come from Si quantum tips of about 20 Å in width and that they are covered by silicon dioxide. © 1999 American Institute of Physics.

Zheng W. H.;Xia Jian-Bai;Lam S. D.;Cheah K. W.;Rakhshandehroo M. R.;Pang S. W.

Applied Physics Letters

1999

The linear character of the polarization of the luminescence in porous Si is studied experimentally, and the corresponding luminescence characteristics in quantum wires are studied theoretically using a quantum cylindrical model in the framework of the effective-mass theory. From the experimental and theoretical results it is concluded that there is a stronger linear polarization parallel to the wire direction than there is perpendicular to the wire, and that it is connected with the valence band structure in quantum confinement in two directions. The theoretical photoluminescence spectra of the parallel and perpendicular polarization directions, and the degree of polarization as functions of the radius of the wire and the temperature are obtained for In0.53Ga0.47 As quantum wires and porous silicon. From the theory, we demonstrated that the degree of polarization decreases with increasing temperature and radius, and that this effect is more apparent for porous Si. The theoretical results are in good agreement with the experimental results for the InGaAs quantum wires, and in qualitative agreement with those for the porous silicon.

Zheng W. H.;Xia Jian-Bai;Cheah K. W.

Journal of Physics Condensed Matter

1997

The electronic structure of an InAs self-assembled quantum dot in the presence of a perpendicular magnetic field is investigated theoretically. The effect of finite offset, valence-band mixing, and strain are taken into account. The hole levels show strong anticrossings. The large strain and strong magnetic field decrease the effect of mixing between heavy hole and light hole. The hole energy levels have in general a weaker field dependence compared with the corresponding uncoupled levels. © 1998 The American Physical Society.

Li Shu-Shen;Xia Jian-Bai

Physical Review B Condensed Matter and Materials Physics

1998

The band structure of the Zn1-xCdxSySe1-yquaternary alloy is calculated using the empirical pseudopotential method and the virtual crystal approximation. The alloy is found to be a direct-gap semiconductor for all x and y composition. Polynomial approximation is obtained for the energy gap as a function of the composition x and y. Electron and hole effective masses are also calculated along various symmetry axes for different compositions and the results agree fairly well with available experimental values.

Feng Y. P.;Poon H. C.;Ong C. K.;Teo K. L.;Li M. F.;Xia J. B.

Journal of Applied Physics

1993

Results of theoretical investigations on hole subbands in quantum wells and superlattices are reviewed. Topic covered include: hole subband calculation by an expansion method; pseudopotential calculation by a two-step procedure; heavy and light hole mixing and Coulomb energy of excitions; other applications of the expansion method. © 1988.

Huang Kun;Xia Jianbai;Zhu Bangfen;Tang Hui

Journal of Luminescence

1988

Electro-modulation mechanisms and related photoreflectance (PR) of quantum wells (QWs) are studied. It is argued that in QWs, unlike in bulk material, the perpendicular electric field does not result in either a Franz-Keldysh effect or an excitonic damping and dissociation effect, but rather in a Stark effect on subband energies, wave functions and oscillator strengths. The PR line shapethus is mainly of first derivative type. The electric field effects on the first and higher sublevels and optic matrix elements are calculated using a stationary state approximation. The spectral lineshapes of PR of QWs are predicted on the basis of the Stark effect modulation of nonexcitonic and excitonic interband transitions. The experimental results agree well with the theoretical analysis. © 1989 Academic Press Limited.

Jiang De-Sheng;Tang Yin-Sheng;Xia Jian-Bai;Enderlein R.

Superlattices and Microstructures

1989

Resonant Raman scattering is investigated on GaInAs/AlInAs multiple quantum well (MQW) heterostructures, lattice-matched to InP substrates. The resonance is realized at several fixed laser lines by varying the hydrostatic pressure to tune the interband transition energies (in the neighborhood of the AlInAs band gap) into resonance. Our tight-binding calculation of the electronic envelope functions shows that the resonance is related to the optical transitions between electron and hole extended states. The strong resonant enhancement of Raman peaks occurs only for AlInAs LO phonons which are confined in the barrier layers, but not for GaInAs LO phonons, providing direct experimental evidence for the spatial distribution of extended excitons. © 1992.

Jiang D. S.;Xia J. B.;Zhang Y. H.;Abraham C.;Syassen K.;Ploog K.

Superlattices and Microstructures

1992

The empirical pseudopotential method within the virtual crystal approximation is used to calculate the band structure of Mg 1-x Zn x S y Se 1-y , which has recently been proved to be a potential semiconductor material for optoelectronic device applications in the blue spectral region. It is shown that MgZnSSe can be a direct or an indirect semiconductor depending on the alloy composition. Electron and hole effective masses are calculated for different compositions. Polynomial approximations are obtained for both the energy gap and the effective mass as functions of alloy composition at the Gamma valley. This information will be useful for the future design of blue wavelength optoelectronic devices as well as for assessment of their properties.

Teo K. L.;Li M. F.;Chong T. C.;Feng Y. P.;Xia J. B.

Semiconductor Science and Technology

1994

Photoluminescence studies on porous silicon show that there are luminescence centers present in the surface states. By taking photoluminescence spectra of porous silicon with respect to temperature, a distinct peak can be observed in the temperature range 100-150 K. Both linear and nonlinear relationships were observed between excitation laser power and the photoluminescence intensity within this temperature range. In addition, there was a tendency for the photoluminescence peak to red shift at low temperature as well as at low excitation power. This is interpreted as indicating that the lower energy transition becomes dominant at low temperature and excitation power. The presence of these luminescence centers can be explained in terms of porous silicon as a mixture of silicon clusters and wires in which quantum confinement along with surface passivation would cause a mixing of Γ and X band structure between the surface states and the bulk. This mixing would allow the formation of luminescence centers. © 1995 Springer-Verlag.

Cheah K. W.;Ho L. C.;Xia J. B.;Li J.;Zheng W. H.;Zhuang W. R.;Wang Q. M.

Applied Physics A Materials Science Processing

1995