Quantum-confined magneto-Stark effect in diluted magnetic semiconductor coupled quantum wells

The magneto-Stark effect in a diluted magnetic semiconductor (DMS) coupled quantum well (CQW) induced by an in-plane magnetic field is investigate theoretically. Unlike the usual electro-Stark effects, in a DMS CQW the Lorenz force leads to a spatially separated exciton. The in-plane magnetic field can shift the ground state of the magnetoexciton from a zero in-plane center of mass (CM)/momentum to a finite CM momentum, and render the ground state of magnetoexciton stable against radiative recombination due to momentum conservation. (C) 2002 American Institute of Physics.

Electron effective mass and resonant polaron effect in CdTe/CdMgTe quantum wells

Cyclotron resonance in CdTe/CdMgTe quantum wells (QWs) was studied. Due to the polaron effect the zero-field effective mass is strongly influenced by the QW width. The experimental data have been described theoretically by taking into account electron-phonon coupling and the nonparabolicity of the conduction band. The subband structure was calculated self-consistently. The best fit was obtained for an electron-phonon coupling constant alpha = 0.3 and bare electron mass of m(b) = 0.092m(0).

Electrical manifestation of the quantum-confined Stark effect by quantum capacitance response in an optically excited quantum well

We have studied the capacitance-voltage characteristics of an optically excited wide quantum well. Both self-consistent simulations and experimental results show the striking quantum contribution to the capacitance near zero bias which is ascribed to the swift decreasing of the overlap between the electron and hole wave functions in the well as the longitudinal field goes up. This quantum capacitance feature is regarded as an electrical manifestation of the quantum-confined Stark effect.

Effect of rapid thermal annealing on GaInNAs/GaAs quantum wells grown by plasma-assisted molecular-beam epitaxy

We have studied the effect of rapid thermal annealing (RTA) on GaInNAs/GaAs quantum wells (QWs) grown by molecular-beam epitaxy using a dc plasma as the N source. It was found that RTA at low temperature (LT, 650 degrees C) and high temperature (HT, 900 degrees C) could both improve the QW quality significantly. To clarify the mechanism of quality improvement by RTA, a magnetic field perpendicular to the path of the N plasma flux was applied during the growth of the GaInNAs layers for the sake of comparison. It was found that LT-RTA mainly removed dislocations at interfaces related to the ion bombardment, whereas, HT-RTA further removed dislocations originating from the growth. LT-RTA caused only a slight blueshift of photoluminescence peak wavelength, probably due to defect-assisted interdiffusion of In-Ga at the QW interfaces. The blueshift caused by HT-RTA, on the other hand, was much larger. It is suggested that this is due to the fast defect-assisted diffusion of N-As at the QW interfaces. As defects are removed by annealing, the diffusion of In-Ga at interfaces would be predominant. (C) 2000 American Institute of Physics. [S0003- 6951(00)01535-7].

Strain effect on the band structure of InAs/GaAs quantum dots

The strain effect on the band structure of InAs/GaAs quantum dots has been investigated. 1 mu m thick InGaAs cap layer was added onto the InAs quantum dot layer to modify the strain in the quantum dots. The exciton energies of InAs quantum dots before and after the relaxation of the cap layer were determined by photoluminescence. When the epilayer was lifted off from the substrate by etching away the sacrifice layer (AlAs) by HF solution, the energy of exciton in the quantum dots decreases due to band gap narrowing resulted from the strain relaxation. This method can be used to obtain much longer emission wavelength from InAs quantum dots.