Structure and properties of InGaAs layers grown by low-temperature molecular-beam epitaxy

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This paper describes studies of InGaAs layers grown by molecular-beam epitaxy on InP (100) substrates at temperatures of 150–480 °C using various arsenic fluxes. It was found that lowering the epitaxy temperature leads to changes in the growth surface, trapping of excess arsenic, and an increased lattice parameter of the epitaxial layer. When these lowtemperature (LT) grown samples are annealed, the lattice parameter relaxes and excess arsenic clusters form in the InGaAs matrix. For samples grown at 150 °C and annealed at 500 °C, the concentration of these clusters was ∼8×1016 cm−3, with an average cluster size of ∼5 nm. Assuming that all the excess arsenic is initially trapped in the form of antisite defects, the magnitude of the LT-grown InGaAs lattice parameter relaxation caused by annealing implies an excess arsenic concentration (N As−N Ga−N In)/(N As+N Ga+N In)=0.4 at.%. For layers of InGaAs grown at 150 °C, a high concentration of free electrons (∼1×1017 cm−3) is characteristic. Annealing such layers at 500 °C decreases the concentration of electrons to ∼1×1017 cm−3. The results obtained here indicate that this change in the free-electron concentration correlates qualitatively with the change in excess arsenic concentration in the layers.