Lateral confinement of carriers in ultrathin semiconductor quantum wells

Localized and extended states in semiconductor quantum wells with wire-like interface islands

“…Most of the attention has been focused on investigating interface interdiffusion, segregation, and roughness [1], which require relatively small supercells. We have recently developed an efficient Green's function method for the calculation of the electronic structure of QWs with one-dimensional (1D) interface islands, and have used it to study the localized and extended states in ultrathin 2 monolayers (ML) wide InAs/InP (001) QWs with 1 ML interface steps [4,5]. We have recently developed an efficient Green's function method for the calculation of the electronic structure of QWs with one-dimensional (1D) interface islands, and have used it to study the localized and extended states in ultrathin 2 monolayers (ML) wide InAs/InP (001) QWs with 1 ML interface steps [4,5].…”

“…Although experimental results have demonstrated the important effect of interface steps on both the extended and the localized states of quantum well (QW) structures [2], only the behavior of localized states has been theoretically studied [3]. The principal effects of this large lateral confining potential have been identified as: i) carrier localization, leading to a large band gap reduction and decrease of the heavy-light hole splitting; and ii) significant changes in the symmetry of the extended (QW) states, which have important implications on the electronic and optical properties of the structures [4,5]. In these structures a change of the QW width by only 1 ML modifies the states' energies by several tens of meV; therefore, their electronic structure is drastically affected by the interface morphology.…”

“…In these structures a change of the QW width by only 1 ML modifies the states' energies by several tens of meV; therefore, their electronic structure is drastically affected by the interface morphology. The islands are oriented along the 010 direction; because of the isotropy of the conduction band (CB), the dependence on the orientation is negligible [4,5]. In wider QWs such as those often used in optoelectronic devices the fluctuations in the QW width give rise to a lateral confining potential of only several meV, therefore their electronic properties should be much less sensitive to the interface morphology.…”

Green’s function matching method for one- and zero-dimensional heterostructures

“…The 2D SGFM theory can be applied also in the special case of 1D systems with planar interfaces; this has been demonstrated in studies of deformed carbon nanotubes 16 and terraces at quantum well interfaces. 12,17 For 1D and 0D systems ͑wires and dots͒ with arbitrary interfaces, the problem is considerably more complicated and requires a complete rederivation of the matching equations taking into account the different topology of the system. Solutions have been found only for continuous systems with a simple symmetry such as a periodic array of cylindrical 1D wires 7 or muffin-tin spheres ͑0D͒.…”

“…To summarize, the SGFM theory has proven to be extremely useful in a wide variety of important computational problems: simulating STM images, 11 semiconductor heterostructures, [12][13][14]17 carbon nanotubes, 16 magnetic multilayers, 15 etc. At present, however, its practical applications are restricted to systems with planar interfaces, due to ͑i͒ the lack of a general SGFM method for 1D and 0D struc-tures with arbitrary interface shapes and ͑ii͒ the lack of efficient algorithms to calculate the interface projections of the domain Green's functions.…”