
D. A. B. Miller, J. S. Weiner and D. S.
Chemla, "Electric Field Dependence of Linear Optical Properties in Quantum Well
Structures: Waveguide Electroabsorption and Sum Rules," IEEE J. Quantum Electron. QE22,
18161830 (1986). The authors report experiments and theory on the effects of
electric fields on the optical absorption near the band edge in GaAs/AlGaAs quantumwell
structures. They find distinct physical effect for fields parallel and perpendicular to
the quantumwell layers. In both cases, they observe large changes in the absorption near
the exciton peaks. In the parallelfield case, the excitons broaden with field,
disappearing at fields approximately 10/sup 4/ V/cm; this behavior is in qualitative
agreement with previous theory and in orderofmagnitude agreement with direct theoretical
calculations of field ionization rates reported in this paper. This behavior is also
qualitatively similar to that seen with threedimensional semiconductors. For the
perpendicularfield case, they see shifts to the exciton peaks to lower energies by up to
2.5 times the zerofield binding energy with the excitons remaining resolved at up to
approximately 10/sup 5/ V/cm: This behavior is qualitatively different from that of bulk
semiconductors and is explained through a mechanism previously briefly described by the
authors (D.A.B. Miller et al., Phys. Rev. lett. 53, 2173 (1984)) called the
quantumconfined Stark effect. In this mechanism the quantum confinement of carriers
inhibits the exciton field ionization. To support this mechanism they present detailed
calculations of the shift of exciton peaks including (i) exact solutions for single
particles in infinite wells, (ii) tunneling resonance calculations for finite wells, and
(iii) variational calculations of exciton binding energy in a field. They also calculate
the tunneling lifetimes of particles in the wells to check the inhibition of field
ionization. The calculations are performed using both the 85:15 split of bandgap
discontinuity between conduction and valence bands and the recently proposed 57:43 split.
Although the detailed calculations differ in the two cases, the overall shift of the
exciton peaks is not very sensitive to split ratio. They find excellent agreement with
experiment with no fitted parameters
Full text available for
download 