Study of dislocation distribution in graded InGaAs/GaAs buffer layers by XRD and DLTS

This work reports on the investigation of the dislocation distribution and their electrical activity in linearly graded InGaAs buffer layers followed by 1.2 mu m thick InxGa1-xAs layer. The buffer composition profiles have been chosen in order to have either strain-free or compressively strained active layers. The residual strain values of the different structures and their dislocation distributions have been determined by X-Ray Diffraction (XRD) (reciprocal space maps, double crystal topography). Electronic states ascribed to threading dislocations in the active layer have also been studied with Deep Level Transient Spectroscopy (DLTS). The DLTS signal amplitude is in qualitative agreement with the dislocation distribution determined by structural characterization techniques.