The 2X2 structure formed on a Ga-adsorbed Si(100) surface is determined using tensor low-energy electron diffraction. I-V curves of the parallel dimer model are in excellent agreement with those of the experiment, indicating that the actual surface has parallel dimer structure. Speci6c displacements of the topmost two surface layers (the protrusion of the Ga dimer toward the vacuum, the increase of the bond length of the Ga dimer, the stretching of the Si dimer, and the movement of the Si dimer toward the Ga dimer) with the elongation of the Si dimer back bond are observed in the optimized geometry. The Ga-Si bond angle measured from the Si(100) surface plane is recovered with these displacements from that of the ideal geometry where each bond length is assumed to be the sum of Pauling covalent radii. Subsurface layers are also deformed to keep the bond lengths near their bulk values.

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Carrier confinement performance by multiple quantum barriers (MQB) is demonstrated in 1.55 μm strained GaInAs/AlGaInAs multiple quantum well (MQW) lasers grown by molecular beam epitaxy. The strained MQW lasers with MQB at p-side optical confinement layer show larger characteristic temperature and slope efficiency at high temperature than those without MQB. It is also shown that the MQW lasers with MQB have less spontaneous emission from the optical confinement layer than the lasers without MQB. As another important result, it is demonstrated for the first time that the MQW lasers with MQB have less dependency of the K factor on the temperature than the lasers without MQB. These results further verify the effective carrier confinement performance of GaInAs/AlInAs MQB structure.

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