| Description |
This work reviews the fundamentals of InGaN materials and of surfactant effects in surfactant-mediated heteroepitaxial growth. The basic surface processes and possible surfactant mechanisms are presented. These principles are then applied to a study of the effects of Sb surfactant on InGaN grown by organometallic vapor phase epitaxy (OMVPE). Eight samples of InGaN were prepared with varying amounts of Sb (0-2.5%) present during growth. The samples were characterized by atomic force microscopy (AFM), photoluminescence (PL), near field scanning optical microscopy (NSOM), scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM). InGaN grown without surfactant was smooth with large, wide islands and low island density. Samples grown with 0.5%, 0.75%, and 1% Sb showed an increase in 3D island growth and displayed a blue PL emission peak (~460 nm). STEM showed an In-rich InGaN film with three dimensional (3D) islanding or quantum dots (QDs) on the surface. Samples grown with 1.25%, 1.75%, 2% and 2.5% Sb showed a drastic increase in 3D island density. These samples showed a green (~550 nm) emission peak. STEM showed a different In distribution, with In-rich QDs on the surface. The sudden change in surface morphology and PL emission peak suggest that Sb induces a different surface reconstruction at a certain threshold concentration between 1% and 1.25% that affects In incorporation or In distribution in the film as well as overall surface morphology. |
