Effect of surface quality on overgrowth of highly strained GaInAs/GaAs quantum wells and improvement by a strained buffer layer

The introduction of a thin strained GaInAs buffer layer is proposed in the metalorganic chemical vapor phase deposition of GaInAs/GaAs quantum wells for greater than or equal to 1.2 mu m wavelength emission. This buffer layer is found to be very effective in improving the surface quality on which highly mismatched GaInAs quantum wells with an indium content around 40% are grown. Atomic force microscopy measurements demonstrate that the insertion of this strained GaInAs buffer layer can reduce the density of three dimensional islands in a highly strained GaInAs layer by one order of magnitude. We show that highly strained GaInAs/GaAs quantum wells with an indium content around 40% are more sensitive to surface quality than in the case of a lower indium content. This technique has enabled us to achieve a high-quality GaInAs/GaAs quantum well laser emitting at a wavelength near 1.2 mu m.