Studies of Misfit Dislocation Densities in II-VI Laser Structures by Diffuse X-Ray Scattering

Abstract

Subject classification: 61.72. Dd; 68.55.Ln; S8.12 ZnSe-based laser structures grown on GaAs(001) substrates were studied by high resolution X-ray diffraction. Extended diffuse scattering observed in reciprocal space maps was found to be caused by misfit dislocations located at the interface between the p-type doped ZnSSe spacer on top of the p-type cladding layer and the subsequent ZnSe layer. Linear densities of dislocations are estimated by simulations.Introduction Dislocation densities in epitaxial heterostructures are usually estimated from etch pit densities or by transmission electron microscopy. As a nondestructive method, diffuse scattering is used to qualitatively describe modifications in defect densities via changes in the characteristic scattering patterns [1,2]. Different models were used in order to quantitatively exploit diffuse scattering, for instance, to study the thermally induced increase in linear misfit dislocations in early stages of relaxation in SiGe layers deposited on Si(001) [3]. While most of the previous studies on diffuse scattering where focused on single layers, we present a detailed study for complex heterostructures. In particular, we studied a series of II-VI semiconductor laser structures.

Bunches of misfit dislocations on the onset of relaxation of Si0.4Ge0.6/Si(001) epitaxial films revealed by high-resolution x-ray diffraction

“…3(d)] looks qualitatively different. It possesses the side maxima described theoretically for uncorrelated random misfit dislocations [16] and observed experimentally for In 0.1 Ga 0.9 As/GaAs(001) [15], Si 0.75 Ge 0.25 /Si(001) [16], and ZnSe/GaAs(001) [17,18] epitaxial films.…”

“…The 60 • dislocations with Burgers vectors 1 /2 011 that glide in the {111} planes are the main type of dislocations in crystals with diamond or zinc blende structure [2][3][4][5]. Calculated and experimental diffraction curves from uncorrelated 60 • dislocations show characteristic side peaks (side lobes on the maps) [15][16][17][18] that are absent in our experimental patterns. Since edge (Lomer type) misfit dislocations are also formed at the SiGe/Si interface as a result of a reaction between 60 • dislocations [19][20][21], we have tried various models for the arrangement of edge dislocations, using the Monte Carlo method [22].…”

Nondestructive evaluation of misfit dislocation densities in ZnSe∕GaAs heterostructures by x-ray diffuse scattering

“…9 This has been used to qualitatively detect changes in defect densities, for instance, in ZnSe layers on GaAs substrates with dependence on growth start conditions 10 or after thermal treatment. 12 In this paper we investigate the possibility to quantitatively use the x-ray diffuse scattering by comparing the misfit dislocation densities that resulted from theoretical profiles for the diffuse scattered intensities, calculated using the model of Kaganer et al, 9 with those that resulted from cathodoluminescence and transmission electron microscopy. 12 In this paper we investigate the possibility to quantitatively use the x-ray diffuse scattering by comparing the misfit dislocation densities that resulted from theoretical profiles for the diffuse scattered intensities, calculated using the model of Kaganer et al, 9 with those that resulted from cathodoluminescence and transmission electron microscopy.…”