Structure and optical properties of (001)GaAs surfaces nitrided in plasma-assisted NH3 gas

Structural and optical studies were made on the (0 0 1)GaAs surfaces nitrid ed at 700 degreesC for 15 min in the pressure between 0.01 and 0.5 Torr, pl asma-assisted NH3 gas atmosphere. Reflection high-energy electron diffracti on (RHEED) and PLS results indicated that the surface nitrided in 0.01 Torr NH gas consisted of cubic gallium nitride (c-GaN) with epitaxial orientati on: (0 0 1), [1 1 0]c-GaN//(0 0 1), [1 1 0]GaAs, showing PL spectrum with s harp, blue emission of lambda = 440 nm and a broad peak approximately 470 n m at room temperature. The surface nitrided in 0.05 Torr NH gas was compose d of a mixture of cubic and hexagonal GaN, showing blue photoluminescence ( PL) emission with wavelength, approximately 440 nm at room temperature. The surface nitrided in 0.5 Torr NH gas consisted of polycrystalline hexagonal GaN, showing blue PL emission with wavelength, approximately 440 nm at roo m temperature. Results of depth profile of the nitrided surface, by AES wit h sputtering technique using argon gas, indicated that the nitrided layers varies approximately 50-1000 Angstrom in thickness, depending on the NH3 ga s pressure, as a GaNAs alloy layer. These results are in reasonable agreeme nt with theoretical prediction on the band-gap energies in GaN-GaAs alloy s ystem. (C) 2001 Elsevier Science B.V. All rights reserved.