In situ control of strain-induced dot structure by arsenic/phosphorus replacement
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By means of in situ arsenic/phosphorus partial pressure control, the metastabilization of transitional surface structures during the coherent reformation and flattening of InGaAs(P) dots has been achieved. Since coherently grown dots are maintained by strain accumulated between the dots and a sublayer, the in situ replacement of arsenic/phosphorus in the several topmost monolayers changes the surface lattice parameter of the dots, and a drastic change in surface structure (the flattening of the dots or their reformation) is induced. The transitional surfaces being metastabilized were observed ex situ by a high-resolution scanning electron microscope and an atomic force microscope, and the process of dot reformation/flattening was made clear. To show the application of in situ phosphidation (the replacement of arsenic by phosphorus) of dots, the step by step reformation of the dots was demonstrated using an AsH3 pulse supply onto the flattened surface. The fabrication of graded-composition dots was attempted by the pulse supply of TEGa or TMIn during the step by step reformation of dots, resulting in a large difference in the intensity of photoluminescence (PL) between Ga-added and In-added dots. Furthermore, the temperature dependence of PL from the transitional structure between dots and a flat surface has been investigated by means of capping the structure with GaAs overgrowth. The effects of dot phosphidation on PL are discussed through comparison with unphosphidated dots.
Key wordsArsenic/phosphorus replacement InGaAs in situ control photoluminescence (PL) self-organized dots
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