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

This paper describes studies of InGaAs layers grown by molecular-beam epita xy on InP (100) substrates at temperatures of 150-480 degrees C using vario us arsenic fluxes. It was found that lowering the epitaxy temperature leads to changes in the growth surface, trapping of excess arsenic, and an incre ased lattice parameter of the epitaxial layer. When these low-temperature ( LT) grown samples are annealed, the lattice parameter relaxes and excess ar senic 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 si milar 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 an tisite defects, the magnitude of the LT-grown InGaAs lattice parameter rela xation 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 degre es C, a high concentration of free electrons (similar to 1x10(18) cm(-3)) i s characteristic. Annealing such layers at 500 degrees C decreases the conc entration of electrons to similar to 1x10(17) cm(-3). The results obtained here indicate that this change in the free-electron concentration correlate s qualitatively with the change in excess arsenic concentration in the laye rs. (C) 1999 American Institute of Physics. [S1063-7826(99)00208-2].