We utilize the sensitivity of the two- to three-dimensional growth transition of InAs self-assembled islands on InAs coverage to demonstrate the growth of self-aligned InAs islands on etched GaAs ridges by molecular beam epitaxy. The different migration behavior of In adatoms on different crystal planes of etched ridges is used to spatially modulate the supply of In adatoms. The ridges are oriented either along the [011] and [011̄] direction on (100) substrates with grating spacing of 0.28, 1, and 5 μm. Atomic force microscopy reveals that the InAs islands are self-aligned along the ridges and they have a typical size of 400 Å in diameter and 120 Å in height. In samples with [011] oriented ridges, the islands are located on the sidewalls. On the other hand, for [011̄] oriented ridges the islands are on the (100) planes on and at the foot of the mesa. On samples with a grating pitch of 0.28 μm, all the islands are located either on the sidewalls or at the bottom of the ‘‘V groove’’ for both grating orientations.

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Calculation of the Schottky barrier height at the Al/GaAs(001) heterojunction: Effect of interfacial atomic relaxations J.

We report on oscillations in the photoreflectance (PR) spectra in the energy range below the band gap of GaAs on samples containing GaAs/AlGaAs quantum wells and the other multilayers grown on Si-doped GaAs substrates. The PR spectra with the quantum well chemically removed continue to show these oscillations, indicating that they are not related to the quantum well. These oscillations, which are probed by the modulation technique, are attributed to the interference effect of two light beams reflected from different interfaces of the sample. These spectra are calculated and good agreement with experimental data is obtained. We find that the interference effect distorts the line shape of the PR features associated with quantum wells and band edge of bulk semiconductors, especially at the low-energy side. Therefore, this effect must be taken into account during analysis. As an application, this interference effect can be used to accurately measure epilayer thicknesses.