Nitrogen surfactant effects in GaInP

The addition of surfactant nitrogen during the growth of GaInP on 001 GaAs substrates produces significant and interesting changes in the optical and morphological properties of GaInP. In particular, multiple peaks are seen in the low temperature photoluminescence (PL) spectra of GaInP/GaInP:N heterostructures. The origin of these multiple peaks is investigated using transmission electron microscopy, energy dispersive spectroscopy, and cathodoluminescence. It is found that a discontinuous In-rich layer forms at the GaInP/GaInP:N interface leading to a 1-6 nm thick GaInP layer that is 70% In and has a PL peak energy of 1.7 eV. Cross-sectional cathodoluminescence experiments confirm the existence and composition of the interface layer. The cathodoluminescence experiments also show that the GaInP:N epilayer produces emission at a higher energy than the GaInP epilayer. Cathodoluminescence monochromatic images of surface pyramids indicate that the pyramids emit at higher energy than the surrounding GaInP:N epilayer. Atomic force microscopy of the pyramids reveals the formation of facets with angles of up to 23°. The large misorientation of the pyramids leads to GaInP material that is more disordered than the top epilayer.