DISLOCATION GENERATION MECHANISMS OF INXGA1-XAS (0-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-1) EPILAYERS GROWN ON (100) INP SUBSTRATES BY MOLECULAR-BEAM EPITAXY

The mechanisms of strain relaxation and dislocation generation for the 2-mu m-thick InxGa1-xAs epilayers grown on (100) InP substrates with 0 less than or equal to x less than or equal to 1 were investigated. It was found that the growth mode and dislocation density of the InxGa1-xAs epilayers are not only dependent on the lattice mismatch with respect to InP substrates, but the abundance of Ga atoms and the degree of cation disorder in the alloy composition also play important roles. In the negative mismatched range even with a medium lattice mismatch (e.g., epsilon=-1.1%), InGaAs alloys with a high degree of cation disorder and containing more Ga atoms (x=0.32-0.37) trigger island growth and introduce high-density V-shaped dislocations. In the positive mismatched range, island growth occurs at x approximate to 0.82 (epsilon=2%) and few V-shaped dislocations are generated. The difference between these two ranges is due to their different Ga concentrations which introduce different island nucleation centers in the initial growth stage.