Applied Electric Field, Impurity States In Rectangular Quantum Wire,

Hydrogenic impurities in low dimensional semiconductor structures have been studied extensively. Electric field applied perpendicularly to the layer of quantum wells can change the optical properties(abstraction, reflection and photoluminesce-nce)of semiconductor quantum well structures. This effect is referred to as the quantum-confined Stark effect (QCSE); it has been studied extensively in the past decades for application of lower optical switches and modulators.Recently, the electro-optical properties have been investigated in the quantum well wires under electric field. Benner and Huang proposed parabolic confinement potential, obsersed QCSE in quantum well wires. Brown and Spector have obtained the binding energy of hydrogenic impurities in cylindrical, infinite-length, GaAs-(GaAl)As QWWs for finite and infinite confinement potential . Weber et al have calculated the density of impurity and energy spectra of hydrogenic impurities in rectangular cross section QWWs without considering the effects of external fields. The effect of an applied electric field on the binding energy ofshallow donor impurities in rectangular cross section GaAs QWWs was presented by Montes et al, by considering an infinite confinement potential and using a variational scheme. For wires with the same transversal section as those of Brown and Spector, they observed the same behavior for the impurity binding energy.Though they discuss the impurity in the QWWs under the electric field in more ditail, they localized the square GaAs/Ga_0.63Al_0.37As QWWs with the infinite potential barrier case. We discuss the QCSE of the impurity in the finite square QWWs considering impurity position , and raise a point of the QCSE under the influence of the masses mismatch and the aspect ratio of the quantum well wires.Without considersion of the mismatch of the effective masses between the well and barrier, we obtain the conclusion as follows:(l)The first band energy of the electron is decreased under the electric field.(2)When the impurity in the center of the well, the binding energy of the impurity is decreased as the strength of applied electric field increased.(3)The electric field breaks the energy degeneracyfor symmetrical impurity position in the well, the results show that the redshift and blueshift of the impurity Stark energy shift as the impurity position.(4)Under the same external electric field, the impurity Stark energy shift is obviously different with the different aspect ratio of the quantum well wires.The influence of the masses mismatch on the impurity Stark energy shift is not prominent.