Temperature dependence of threading dislocation density in In0.2Ga0.8As layers grown on GaAs substrates by metalorganic-vapor phase epitaxy

In0.2Ga0.8As layers were grown on GaAs substrates with graded buffer layers by metalorganic vapor phase epitaxy at 370-630 °C. Good surface morphology with a crosshatch pattern (CHP) was obtained at 600 and 630 °C. Transmission electron microscopy (TEM) observation confirmed that the cap layers had a threading dislocation density of between 1.3 and 2.0×106 cm−2. At 500 °C, a layer showed a rough surface morphology. Phase separation was revealed by TEM. The threading dislocation density was over 1×107 cm−2 at 500 °C. Good surface morphology with a CHP was obtained at 430, 450 and 480 °C. A layer grown at 430 °C showed the lowest threading dislocation density of 2.5×105 cm−2. Low temperature growth was effective for lowering the threading dislocation density in the cap layers.