Microstructure and strain relaxation in organometallic vapor phase epitaxy of strain-compensated GaInP/InAsP multilayers on InP(001)

Abstract

The various mechanisms responsible for the strain relaxation of strain-compensated GaInP/InAsP multilayers grown on InP(001) using low-pressure organometallic vapor-phase epitaxy (LP-OMVPE) were investigated using a combination of transmission electron microscopy (TEM), high-resolution x-ray diffraction (HRXRD), and reciprocal lattice mapping. We examined separately the effect of the misfit strain f as well as the total strain energy εT on the strain relaxation mechanisms. We also investigated the effect of the growth temperature Ts on roughening. For the structures composed of a small number of superlattice periods, N=10, TEM and HRXRD indicate that strain relaxation occurs essentially through non-homogeneities at the interfaces for increasing misfit strain f values (at least up to |f|=1%, the largest strain used in these experiments). In comparison, when the magnitude of the misfit strain is kept constant, increasing the number of periods eventually leads to a massive generation of dislocations in the multilayer. For |f|=0.75%, coherency breakdown was observed around the 14th–15th period in a 50-period sample. However, the strain-compensated multilayer structures can be in a metastable state since all layers are perfectly flat and no dislocations are visible in a 20-period sample with the same misfit strains in the layers. Finally, we observed that the growth temperature Ts had a drastic effect on the morphology of the layers: increasing Ts from 620 to 680 °C while keeping all other growth parameters constant introduced large periodic lateral thickness modulations as well as dislocation clusters in the structures. Diffraction contrast analysis in plan-view TEM indicates significant anisotropy with the features elongated in the [11̄0] direction. These results could be used as guidelines for the design of highly perfect and reliable device structures grown by LP-OMVPE.

Thickness modulation and strain relaxation in strain-compensated InGaP/InGaP multiple-quantum-well structure grown by metalorganic molecular beam epitaxy on GaAs (100) substrate

“…In summary, a comparison of The anisotropic thickness modulation mentioned above has already been reported for strain-compensated MQW structures of other material systems, such as InGaAs(P) and InAsP [15][16][17]. As in those previous studies, growth of the compressive-strained well layers is more favorable on locally thin regions of the tensile-strained barrier layer, and also the thickness modulation can be suppressed by decreasing the substrate temperature [18,19]. In contrast, for the other material systems, a compressive strain larger than 1.5% is usually required to induce the thickness modulation in the MQW region within a small number of periods [17,20].…”

Strain-compensated GaInAs/AlInAs/InP quantum cascade laser materials

“…These values are slightly less than that measured for LM MQWs and may be explained by the reduced AlInAs barrier layer thickness in the SC MQWs. Thus, under the presently described growth conditions, there is no degradation in the atomic step structure of 1.5% SC MQWs, and the surface remains stable from the onset of growth until the end, with no indication of strain-induced surface modulation [22]. It is noted that the orientation of the steps shown in Fig.…”

“…Organometallic vapor phase epitaxy (OMVPE) was used for the growth of AlInAs/GaInAs/InP SC materials and QCLs with strain levels of 1 and 1.5%. In previous studies on growth of SC multiple-quantum-wells (MQWs) with compressive-GaInAs/tensile-GaInAs and GaInP/InAsP, it was reported that the photoluminescence and interfaces of SC MQWs degraded with increasing layer strain and increasing number of periods [20][21][22]. Those studies also showed that material quality could be improved by decreasing growth temperature, increasing V/III ratio, and minimizing or eliminating growth interruptions.…”

Microstructural characteristics and crystallographic evolutions of Ga-doped ZnO films grown on sapphire substrates at high temperatures by RF magnetron sputtering

“…[11][12][13][14]. Based on the microstructural characterization and d-spacing, it is believed that the surface protrusions are formed by surface undulation below a critical thickness.…”