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Articles you may be interested inEffect of quantum confinement on shallow acceptor transitions in δ-doped GaAs/AlAs multiple-quantum wells Appl. Phys. Lett. 84, 735 (2004); 10.1063/1.1644912Effect of quantum-well confinement on acceptor state lifetime in δ-doped GaAs/AlAs multiple quantum wells Appl.

Some aspects of the morphology of InAs island formation on InP have been studied by atomic force microscopy, photoluminescence, photoluminescence excitation spectroscopy, and Raman scattering. The InAs layer is grown by chemical beam epitaxy on top of InP surfaces with sawtooth-like channels. The deposition of a thin InAs layer results in quantum dots strongly aligned along the InP channels. Subsequent annealing in an arsenic atmosphere produces growth and loss of coherency of the islands. Atomic force microscopy shows the changes in size and alignment of the islands. Optical measurements serve to give quantitative estimates of the strain distribution among the top of the InP buffer layer, the wetting layer and the islands for the differently treated samples.

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We report on the change of character, from an "isolated" well to a superlattice, of multiple bdoped structures as a function of the doping period d, . This e8'ect is evidenced by the drastic change in the photoluminescence excitation spectra and the deviation on the total electron density extracted from Shubnikov -de Haas oscillation measurements as d, decreases. Self-consistent-calculation results performed for these systems are used for comparison.Multiple b-doped GaAs structures have been widely investigated lately.The variation of the doping period, d"has been shown to strongly afkct the properties of such systems. Results from self-consistent calculations, based on the design parameters, have shown that the characteristic energy level scheme of an isolated b potential is replaced by a set of minibands of finite width, reflecting a superlatticelike behavior, when d, decreases. ' From the experimental point of view, optical techniques, such as photoluminescence (PL), have proved to be extremely useful in the study of the properties of such structures. EfFects associated to miniband formation and confinement of photogenerated holes, as d, decreases, have been reported.In this work we report on the experimental observation of a change in character of these systems, from quasibidimensional (isolated h well) to tridimensional (b-superlattice).The combination of photoluminescence excitation spectroscopy (PLE) with the transport (Shubnikov -de Haas oscillations) measurements allows us to avoid misleading interpretations of the data. To reinforce our point of view we also show results of a selfconsistent calculation based on the transport results.The multiple b-doped samples were grown by molecular beam epitaxy (MBE), on (100)GaAs semi-insulating substrates.The temperature was 540 C to minimize Si diffusion and segregation. The growth rate determined from the reflection high-energy electron-difFraction (RHEED) oscillations was 1.1 ttjh. The "stop-and-go" procedure, which was used to introduce a dopant plan, was repeated to provide the periodic structures, with a nominal Si atoms sheet concentration of 3x10 cmThe width of the intrinsic GaAs layer separating adjacent dopant plans was varied from 40 to 1000 A, and the resulting structures consist of 50 -100 periods. PLE measurements were performed with the samples immersed in superfluid He (2 K). The excitation source in the PLE experiments was a Kr+ pumped LD 700 tunable ring dye laser. The emission spectra were analyzed with a 0.75-m double monochromator and detected by a liquid nitrogen cooled S1 photomultiplier and an electrome-22 C0