A comparative study of heterostructures InP/GaAs (001) and InP/GaAs (111) grown by metalorganic chemical vapor deposition

Abstract

Heteroepitaxial InP layers were grown under the same growth conditions by metalorganic chemical vapor deposition on (001), (111)A, and (111)B surfaces of GaAs substrates. The heteroepilayers were studied by transmission electron microscopy, high-resolution x-ray diffraction, low-temperature photoluminescence, and low-temperature photoluminescence excitation. It is demonstrated that good quality InP epitaxial layers can be grown on GaAs substrates. Since layers and substrates have the same crystal structure, but different lattice parameters (aGaAs=5.6535 Å, aInP=5.8687 Å), the accommodation at the interface may occur by the formation of misfit dislocations parallel to the heterointerface. A remarkable reduction of the threading dislocation density for the (111) orientation and a decrease in the full width at half maximum values of the x-ray diffraction peaks were obtained. These results signify a dramatic crystalline improvement due to the reduction of the dislocation density using (111)-oriented GaAs substrates. The efficient photoluminescence and the full width at half maximum of the exciton peak compared with that of InP homoepitaxy show that good quality InP epilayers can be obtained on (111)-oriented GaAs substrates. The strain relaxation was investigated by high-resolution x-ray diffraction, and low-temperature photoluminescence excitation. The difference between the optical and the x-ray diffraction results is attributed to the thermoelastic strain due to the difference in the thermal expansion coefficients between epilayers and substrates.