Composition uniformity characterization and improvement of AlGaAs/GaAs grown by molecular beam epitaxy

The characterization methods of composition uniformity for AlxGa1-xAs layers have been evaluated. The composition measurement errors by using high resolution X-ray diffraction and room-temperature photoluminescence measurements are both around 1% for AlGaAs with Al composition around 0.3, suggesting that the composition uniformity of lower than ± 1% cannot be verified through these two characterization methods. The effects of manipulator temperatures on the uniformity of AlGaAs/GaAs epitaxial layers grown by molecular beam epitaxy were also investigated. By using a higher manipulator temperature, the composition uniformity across the 4-in. wafers has been improved. The uniformity of the mobility at 77 K for the AlGaAs/GaAs high electron mobility transistor films turns out much more sensitive to the manipulator temperatures, and has been significantly improved by using a higher manipulator temperature.