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Dislocation bending and stress evolution in Mg-doped GaN films on Si substrates
摘要： P-type doping using Mg is essential for realizing a variety of electronic and optoelectronic III-nitride devices involving hetero-epitaxial thin films that also contain a significant number of dislocations. We report on the effect of Mg incorporation on dislocation and stress evolution during the growth of GaN thin films by using in situ curvature measurements and ex situ transmission electron microscopy. A complete picture involving the interplay between three effects—dopant size effect, dislocation bending, and polarity inversion—is presented. Mg aids dislocation bending, which in turn generates tensile stresses in Mg-doped GaN films. As a result, the compressive stress expected due to the dopant size difference effect can only be discerned clearly in films with dislocation densities below 5 × 10^9 cm^?2. Polarity inversion at doping exceeding 10^19 cm^?3 is associated with a sharp drop in screw dislocation density. A kinetic stress evolution model has been developed to capture dislocation bending and size difference effects, and a match between calculated bending angle from the model and that measured from TEM images is obtained.
关键词： Mg doping,stress evolution,dislocation bending,in situ curvature measurements,transmission electron microscopy,polarity inversion,GaN
更新于2025-09-23 15:23:52
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Eutectic Formation, V/III Ratio, and Controlled Polarity Inversion in Nitrides on Silicon
摘要： The crystallographic polarity of AlN grown on Si(111) by plasma-assisted molecular beam epitaxy is intentionally inverted from N-polar to Al-polar at a planar boundary. The position of the inversion boundary is controlled by a two-step growth process that abruptly changes from Al-rich to N-rich growth conditions. The polarity inversion is induced by the presence of Si, which is incorporated from an Al–Si eutectic layer that forms during the initial stages of AlN growth and floats on the AlN surface under Al-rich growth conditions. When the growth conditions change to N-rich, the Al and Si in the eutectic react with the additional N-flux and are incorporated into the solid AlN film. Relatively low levels of Al–Si eutectic formation combined with lateral variations in the Si incorporation lead to nonuniformity in the polarity inversion and formation of surprisingly narrow, vertical inversion domains. The results suggest that intentional incorporation of uniform layers of Si may provide a method for producing polarity engineered nitride structures.
关键词： AlN,Si incorporation,scanning transmission electron microscopy,polarity inversion,nitride structures,eutectic layer
更新于2025-09-16 10:30:52