In-situ optical reflectance and synchrotron X-ray topography study of defects in epitaxial dilute GaAsN on GaAs

Abstract

In order to investigate the possibilities of in-situ monitoring of GaAsN bulk layer growth and the crystal quality concerning the formation of misfit dislocations, GaAsN bulk samples with different layer thicknesses were grown using a metal-organic vapor phase epitaxy system equipped with a normal incidence optical reflectance setup. High-resolution X-ray diffractometry and synchrotron radiation X-ray topography were used to characterize the samples after growth. Combining the results from topography images and in-situ reflectance data, the formation of the misfit dislocations can be roughly identified from the reflectance curves and thus observed during growth.

Strain relaxation induced surface morphology of heterogeneous GaInNAs layers grown on GaAs substrate

“…The cross-hatch surface morphology is usually recognized to be directly related with strain relaxation via threading dislocation glide which results in both surface step and misfit dislocation formation [9,10]. Such a morphology is often observed during strain relaxation in many III-V lattice mismatched semiconductor systems, such as GaInAs/GaAs [11,12] or GaNAs/GaAs [13,14].…”

“…dislocation nucleation and glide. As a consequence, the asymmetric 2D network of  and  dislocations, running in two perpendicular 110 directions is usually formed, resulting in anisotropic misfit strain relaxation of the epitaxial layer in these directions [11][12][13][14][15][16][17]. Indeed, our previous studies on the GaInNAs/GaAs heterostructure showed a distinct anisotropy of strain relaxation related to the asymmetry in formation of interfacial dislocation network [8].…”

Anisotropy of strain relaxation in heterogeneous GaInNAs layers grown by AP-MOVPE

“…The resultant undulating surface morphology, known as a cross-hatch pattern, is formed. The crosshatch morphology is often observed after strain relaxation of many (001)-oriented cubic semiconductor systems, such as GeSi/Si [12], GaInAs/GaAs [13,14], or GaNAs/GaAs [15] and it is usually recognized to reproduce a network of underlying interfacial misfit dislocations. A detail analysis of the GaInNAs surface morphology, related to formation of a misfit dislocations network, will be the subject of our forthcoming investigations.…”