Ultrashort pulse ultraviolet laser treatment of n(100) GaAs: Microstructural modifications and passivation effects

Gallium arsenide (GaAs) is one of the most important materials among the II I-V family, especially in view of its applicability to optoelectronic devic es. However, it is known that GaAs, unlike silicon (Si), does not possess a stable native oxide that can passivate and protect the surface. This artic le reports the use of femtosecond (fs) laser-based modification and passiva tion of the GaAs surface, where femtosecond laser-based processing was show n to be particularly useful, effective, and more convenient compared to con ventional laser treatment. The fs laser treatment involves an almost nonexi stent heat affected zone, which implies that there is virtually no thermal damage to the volume of material surrounding a processed region. The surfac e passivating effects were confirmed by depth-profiling x-ray photoelectron spectroscopic measurements. In addition, scanning electron microscopy and atomic force microscopy measurements lead to a possible explanation of the passivation mechanism. Further, a relatively novel technique called thermal ly stimulated exoelectron emission was used to verify the existence of surf ace passivation. This measurement technique detects "cold electron emission " from trapping centers at the surface of material under scrutiny. (C) 2001 American Institute of Physics.