A density functional theory study of dual surfactant effect in enhancing P-type doping in III-V semiconductors.

摘要

Surfactant effects are usually achieved by the addition of a single surface element. We demonstrate by density functional theory calculations a dual-surfactant effect of Sb and H on enhancing Zn, Mg, Be and Cd incorporation in OMVPE grown GaP thin films. The combined effects of Sb and H lower significantly the film doping energy during the epitaxial growth of all the p-type dopants studied, while neither Sb nor H canh work alone as effectively. The role of H is to satisfy the electron counting mle. The role of Sb is to serve as an electron reservoir to help electron redistribution. We also predict that due to the low electronegativity of Mg, Sb and H will enhance Mg doping the least among these dopants because Mg as an electron reservoir itself may negate the electron reservoir effect of Sb. Our finding suggests a general strategy for enhancing p-type doping of III-V semiconductors by using a metallic-element with H as dual-surfactants and provides an important general physical understanding for p-type doping in III-V thin films.;We also discovered an intriguing dopant induced electronic stress effect. First principles calculation reveals that even if a dopant has the same atomic size as the host atom it substitutes, it still induces a lattice stress of electronic origin, because it has either one more or one less electron than the host. In general, an n-type dopant induces a compressive electronic stress, and a p-type dopant induces a tensile stress. We also found that the electronic stress exhibits a nonlinear dependence on strain, different from the conventional atomic stress effect. The discovery of electronic stress has significant implications in using external strain to enhance doping. In general, the competition between the atomic stress and electronic stress determines the overall stress induced by a dopant, which in turn determines how external strain will change the doping energy.