Growth and characterization of gallium arsenic nitride compound semiconductors

GaN is a direct bandgap semiconductor that exists in the stable wurtzite phase (αGaN, E_g = 3.4eV) and in the metastable zincblende phase (βGaN, E_g = 3.2eV). Recently, it has been shown when βGaN is alloyed with GaAs, an unusually large bandgap bowing coefficient (5eV ∼ 20eV) develops in the GaAsN alloy. This alloy is receiving considerable interest from the fiber optic telecom industry for producing laser devices tunable in the important IR range. Due to the extremely low solubility limit of nitrogen in GaAs (10−9 mole%) however high quality alloy films have been difficult to grow. In this research, GaAsN alloy samples with nitrogen content up to 1.8% were successful grown using arsine, plasma enhanced nitrogen, and triethylgallium on (001) GaAs substrates. The films were grown by chemical beam epitaxy and characterized using transmission electron microscopy, X-ray diffraction and reciprocal space mapping. Results showed the processing parameter window for the GaAsN alloy growth occurred only when the nitrogen flux was approximately twice the arsenic flux, while keeping the group V/III ratio > 12. The film grew as GaAs when the nitrogen flux < 2x arsenic flux, or the film grew as phase segregated GaAs and GaN phases when the nitrogen flux > 2x arsenic flux. The use of different precursor also effected the film growth. A processing parameter window for GaAsN alloy did not exist when dimethyhydrazine (DMHy) and dimethylaminoarsenic (DMAAs) were used together as alternative nitrogen and arsenic sources respectively. Reflective high-energy electron diffraction was used to study the in-situ surface reaction behavior of the different precursors. A purposed model postulates the monomethylaminoarsenic species on the growth surface undergoes a beta-hydride elimination reaction leaving an adsorped H(ad) species on the surface. The H(ad) reacts with N(ad) species from the DMHy resulting in GaAs growth. When the flux of DMHy >> DMAAs, the film grew as phase segregated growth or as GaN.