Synthesis and characterization of nitrogen-rich gallium nitride arsenide alloys.

摘要

The last decade has witnessed rapid development in the understanding and implementation of wide band gap semiconductors, such as gallium nitride and related compounds. At the same time, the advances in already mature gallium arsenide-based technology continue to follow the success of previously conducted material synthesis studies. The possibility of forming ternary and quaternary alloys combining both nitrides and arsenides has become one of the latest frontiers of compound semiconductor research. While arsenic-rich GaNAs alloys have been synthesized and studied by several groups, the alloys containing small percentage of arsenic in the gallium nitride matrix are less thoroughly explored.; In the course of the present investigation, nitrogen-rich GaNAs alloys containing 3–4% of arsenic anion fraction were successfully synthesized by metalorganic chemical vapor deposition—arsenic content in these films constitutes the highest level of incorporation reported to date. Structural and optical characterization of GaNAs phase resulted in a conclusion that arsenic participates in a metastable alloy formation, and phase segregation into binary GaN and GaAs phases occurs only upon annealing of the films. It was demonstrated that substrate plays a significant role in stabilizing the ternary nitrogen-rich phase, which is most likely to form on GaN template. Band gap reduction as a result of arsenic incorporation was quantified based on the optical transmission spectra, yielding an estimate for the bowing parameter of 25 eV in the films with the arsenic content of 3.5%.; In addition, other growth regimes were investigated, such as arsenic doping of high quality GaN layers, and variation of arsenic content in the films with the change in growth temperature. Arsenic incorporation at the doping levels was shown to improve transport and optical properties of GaN layers. Future research effort in the area may focus on obtaining P-type material with the band gap lower than that of GaN, by simultaneous incorporation of arsenic and magnesium in GaNAs films.