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

This paper describes studies of InGaAs layers grown by molecular-beam epitaxy on InP (100) substrates at temperatures of 150-480 degrees 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 low-temperature (LT) grown samples are annealed, the lattice parameter relaxes and excess arsenic clusters form in the InGaAs matrix. For samples grown at 150 degrees C and annealed at 500 degrees C, the concentration of these clusters was similar to 8x10(16) cm(-3), with an average cluster size of similar to 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 degrees C, a high concentration of free electrons (similar to 1x10(18) cm(-3)) is characteristic. Annealing such layers at 500 degrees C decreases the concentration of electrons to similar to 1x10(17) 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. (C) 1999 American Institute of Physics. [S1063-7826(99)00208-2].