SELECTIVE-AREA LOW-PRESSURE MOCVD OF GAINASP AND RELATED MATERIALS ON PLANAR INP SUBSTRATES

Low-pressure MOCVD has been used to grow layers of InP, InGaAs, GaInAsP and quantum well material on planar substrates patterned with silica masks. The thicknesses and, where relevant, the compositions of these selectively grown layers were investigated by optical and scanning electron microscopy, Surface profiling, energy dispersive x-ray analysis, secondary-ion mass spectroscopy and spatially resolved photoluminescence. The epitaxial layers were found to be both thicker and richer in indium in the vicinity of a mask. The perturbations in the thickness and composition of material grown around a given mask pattern were independent of the orientation of the pattern with respect to the gas flow and the crystallographic axes of the substrate. Lateral movement of material from the masked regions to the surrounding areas was found to take place in the gas above the wafer surface. A gas-phase diffusion model based on Laplace's equation was used to analyse the thickness and compositional variations caused by selective growth. The emission wavelength of selectively grown InGaAs/GaInAsP GaInAsP MQW material was shifted by over 100 nm without degradation in emission efficiency. The lasing wavelength of Fabry-Perot lasers fabricated on such material was increased by a similar amount without degradation of threshold current.