Intense laser field effect on the interband absorption in differently shaped near-surface quantum wells
Introduction
The optical absorption associated with the excitons in semiconductor quantum wells (QWs) have been the subject of a considerable amount of work for the reason that the exciton binding energy and oscillator strength in QWs are considerably enhanced due to quantum confinement effect [1], [2], [3], [4], [5]. In recent years, InGaAs/GaAs QW structures have attracted much interest because of their promising applications in optoelectronic and microelectronic devices [6], [7], [8], [9].
As a distinctive type of dielectric quantum wells, the near-surface quantum wells (NSQWs) have involved increasing attention due to their potential to sustain electro-optic operations under a wide range of applied electric fields [10]. In these heterostructures the QW is located close to vacuum and the semiconductor–vacuum interface, which is parallel to the well plane, introduces a remarkable discrepancy in the dielectric constant resulting in a significant enhancement of the exciton binding energy [11], [12]. More recently, a basic phenomenon such as dielectric mismatch effect on the electronic energy levels, impurity states and excitonic absorption spectra in various semiconductor nanostructures [13], [14], [15], including InGaAs/GaAs symmetrical NSQWs [16], has been investigated.
The electronic and optical properties of the semiconductor QWs are significantly modified by applying intense high-frequency laser fields and this effect provides new degrees of freedom for practical applications [17], [18], [19], [20], [21]. As the rapid advances in modern growth techniques and researches for InGaAs/GaAs QWs [22], [23] create the possibility to fabricate such heterostructures with well-controlled dimensions and compositions, the asymmetrical InGaAs/GaAs NSQWs become interesting and worth studying systems.
The aim of this Letter is to investigate the interband optical transitions in differently shaped NSQWs with symmetrical/asymmetrical barriers subjected to intense high-frequency laser fields. We took into account an accurate form for the laser-dressing confinement potential as well as the presence of the image-charges. Within the framework of a simple two-band model the consequences of the exciton–surface interaction and laser field intensity on the absorption spectra have been investigated. To the best of our knowledge this is the first research concerning the intense laser field (ILF) effect on the interband optical transitions in differently shaped NSQWs with asymmetrical barriers.
This Letter is organized as follows: in Section 2 the theoretical model for the ILF effect on the exciton ground energy and interband transitions in differently shaped NSQWs, taking into account the repulsive interaction between carriers and their image-charges, is described. The single-particle wave functions in square (SQW), graded (GQW), and semiparabolic (sPQW) near-surface QWs are obtained by using the matrix transfer method in the effective mass approximation. In Section 3 the numerical results for the 1S-exciton binding energy and interband absorption coefficient in differently shaped InGaAs NSQWs with symmetrical/asymmetrical GaAs barriers and different cap layer thicknesses are discussed. Finally, our conclusions are summarized in Section 4.
Section snippets
Theory
We consider an InGaAs NSQW embedded between asymmetrical GaAs barriers. According to the effective mass approximation, in the absence of the laser field, the exciton Hamiltonian is Here are the single-particle 1D Hamiltonians. The symbol denotes the electron (hole) and is the confinement potential in the growth direction (band-offset potential).
For a square NSQW, has the well-known form:
Numerical results and discussion
The numerical calculations were carried out for In0.18Ga0.82As/GaAs differently shaped NSQWs with the well width and various cap layer thicknesses, , 80 Å, 120 Å, by using the material parameters [12] listed in Table 1 and a broadening parameter [18].
For two nanostructures, GQW and sPQW, one of the GaAs barriers (the cap layer) has an unchanged height, (electron) or (hole), and the other barrier is variable, . The following values for the asymmetry parameter
Conclusions
The electronic properties and absorption spectra for excitons located in differently shaped NSQWs with symmetrical/asymmetrical barriers, under a non-resonant high-frequency laser field, have been investigated. By using the effective mass approximation and a matrix transfer method the ground exciton state energy and absorption coefficients for interband transitions in a wide range of laser intensity, , and barriers asymmetry, σ, have been calculated. Our results reveal that, by tuning the
Acknowledgements
The author would like to express her special thanks to Professor E.C. Niculescu for helpful discussions and constant support.
References (38)
- et al.
Physica E
(2010) - et al.
Superlatt. Microstruct.
(2010) - et al.
Phys. Lett. A
(2003) - et al.
Physica E
(2009) Phys. Lett. A
(2010)- et al.
Superlatt. Microstruct.
(2009) - et al.
Curr. Appl. Phys.
(2010) - et al.
Phys. Lett. A
(2003) - et al.
Phys. Rev. B
(1981) - et al.
Phys. Rev. B
(1990)
Phys. Rev. B
J. Chem. Phys.
J. Phys.: Conf. Ser.
Appl. Phys. Lett.
Appl. Phys. Lett.
Phys. Rev. B
Appl. Phys. Lett.
J. Appl. Phys.
Phys. Rev. B
Cited by (20)
The effects of the intense laser field on the resonant tunneling properties of the symmetric triple inverse parabolic barrier double well structure
2020, Physica B: Condensed MatterCitation Excerpt :The effects of an intense laser field on the physical properties of low dimensional semiconductors have been a remarkable topic due to the advent of a high-power, long-wavelength, linearly polarized laser sources. This situation has initiated the discovery of interesting physical phenomena associated with the laser field [27–36]. The intense laser field effects on the inter-band transitions in GaAs–Ga1-xAlxAs quantum wells having power-exponential confinement potentials have been investigated by Niculescu et al. [31].
Influence of image charges on the impurity-related optical properties of near-surface quantum wells under a transverse electric field
2019, Physica E: Low-Dimensional Systems and NanostructuresInfluence of image charge effect on the binding energy of hydrogen-like donor impurity in a near-surface quantum well under transverse electric field
2019, Physica E: Low-Dimensional Systems and NanostructuresCitation Excerpt :In NSQW structures the QW plane is parallel to the semiconductor-vacuum interface and separated from vacuum by a thin barrier layer. The electronic structure and, consequently, the optical properties of the NSQWs are sensitive to the dressed well induced asymmetry and the effects of external fields [15–21]. Therefore, the barrier layer in NSQW allows to perform electro-optic operations under a larger range of applied fields.
Linear and nonlinear magneto-optical absorption in a quantum well modulated by intense laser field
2016, Superlattices and MicrostructuresCitation Excerpt :Duque et al. [25] investigated the intense laser effects on nonlinear optical absorption and optical rectification in single quantum wells under applied electric and magnetic field. Eseanu [26] calculated the intense laser field effect on the interband absorption in differently shaped near-surface quantum wells. It is well known that the effect of the laser field leads to the modifications in the potential shape of quantum well structure and therefore effect on the linear and nonlinear optical properties.