A two-step wet chemical etching process using HBr and HBr:K2Cr2O7 was developed in order to fabricate high-quality V-grooves in InP (100) wafers. A 40 nm titanium film, which was patterned by conventional photolithography and liftoff, was used as the etching mask. The {111}A sidewalls are mirrorlike with an arithmetic average roughness of less than 0.4 nm. The tip radius of the V-grooves is approximately 7 nm. Both values were determined by atomic force microscopy. InfrocluctionEver since they were first suggested, low-dimensional structures have generated wide interest. Due to their reduced dimensionality, the electronic density of states is increasingly confined from the common square-root dependence in bulk semiconductors through a steplike function for two-dimensional quantum wells (QWs) and sawtooth-like singularities for one-dimensional quantum wires (QWRs) to S functions for zero-dimensional quantum dots (QD5).' From the device point of view, the steady constriction of the density of states has several beneficial results, since basically the distribution of electrons and holes over a wide energy range is eliminated, thus leading to improved device characteristics. For lasers with quantum structures as the active region, the threshold current density becomes smaller' and less temperature-sensitive2 with decreasing dimensionality. Simultaneously, the optical gain increases dramatically.' Due to the modified density of states, the linewidth-enhancement factor is expected to be extremely small,3 which leads to improved noise behav-ior3'4 and increased relaxation oscillation frequency.3A QW laser can be easily grown on planar substrates by controlling the growth time. The main impediment of realizing QWR and QD lasers is the very size of the quantum structures in two or three dimensions lying in the range of de Broglie's wavelength.GaAs/AlGaAs QWR lasers have been fabricated using anisotropic growth in V-grooves.5 Conventional lithography in combination with wet chemical etching was used to fabricate the V-grooves. The lateral current confinement was realized by H-implanted areas which must be aligned with a precision of less than 1 p.m. Such accurate alignment is unnecessary if a set of QWRs is used in parallel.6 Lasers with strained self-organized QD5 grown in the Stranski-Krastanov mode were demonstrated.7 The

We studied the diffusion process in metalorganic vapor-phase epitaxy of InGaAs on V-groove patterned InP substrates. A model, recently developed for selective-area growth on planar patterned substrates, enabled us to analyze growth rate distribution and to determine diffusion lengths of growing species. Atomic force microscopy (AFM) and photoluminescence measurements have been employed to measure the growth rate and composition of the ternary alloy. A new technique based on composition sensitive etching combined with etch rate measurements by cross-section AFM reveals the reduced solidifying probability of Ga on {111}A planes as the origin of compositional variations.

We report on magneto-optical Kerr-ellipticity measurements with different In 0.53 Ga 0.47 As/InP multiquantum-wells at room temperature. These samples are grown with nominally the same sample parameters, except for the barrier thickness, which for one sample is small enough for a coupling between the quantum wells. The spectral range covered the quantum-well interband transitions of the electron-heavy-hole ground states. The magneto-optical spectra show a number of oscillations, whose spectral position depends on the magnetic-field strength. For model calculations, Lorentzian line shapes for the off-diagonal element of the dielectric tensor have been used. Magneto-optical interference effects are carefully discussed. For small magnetic fields, the shift of the ground state shows a diamagnetic behavior. For the coupled quantum well a transition into the high-field regime can be seen at BϷ9 T. Due to the higher exciton energy for the uncoupled system, high-field behavior occurs only at fields beyond the range of the present experiments. Model calculations allow us to estimate from the shift of the ground state (1s), the exciton binding energy and the dimensionality of the system. According to these calculations the uncoupled sample shows a more 2D-like ͑where 2D is two-dimensional͒ behavior, while the coupled system is more 3D like. The higher levels, however, are typical for Landau splitting. For these the excitonic effect is negligible compared to the Landau shift. In our experiments, we were able to trace the oscillations up to 200 meV above the band gap of unstrained In 0.53 Ga 0.47 As bulk material. This allows us to determine the energy dependence of the reduced effective mass at room temperature. Using the three-band Kane model for the calculation of the electron effective mass, we find that the hole effective mass in In 0.53 Ga 0.47 As quantum wells is significantly lower than in bulk material.

Articles you may be interested inDilute nitride InGaAsN/GaAs V-groove quantum wires emitting at 1.3 μm wavelength at room temperature Appl. Phys. Lett. 99, 101107 (2011); 10.1063/1.3610950 High-quality 1.3 μm-wavelength GaInAsN/GaAs quantum wells grown by metalorganic vapor phase epitaxy on vicinal substrates Appl. Phys. Lett. 99, 072116 (2011); 10.1063/1.3623478 Narrow inhomogeneous broadening of V-groove quantum wires grown on vicinal substrates Appl. Phys. Lett. 93, 172107 (2008); 10.1063/1.2976555Effect of growth temperature on strain barrier for metalorganic vapor phase epitaxy grown strained InGaAs quantum well with lattice matched InGaAsP barriers

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