Growth and Annealing Temperature Dependences of Crystal Structure of Low-Temperature-grown In_xGa_1-xAs on InP Substrate

Abstract

Low-temperature-grown (LTG) In_xGa_1-xAs with thicknesses of 2.0 μm on InP substrates were grown by molecular beam epitaxy at a substrate temperature of 200-240 ℃; they were characterized by high-resolution X-ray diffraction (XRD), Rutherford backscattering spectrometry (RBS), and X-ray reciprocal space mapping (RSM) measurements. While XRD peaks and RBS channeling dip curves were observed for LTG In_0.45Ga_0.55As samples grown at 220 ℃, there were no peaks and dip curves for LTG In_0.44Ga_0.56As samples grown at 200 ℃ in XRD and RBS channeling measurements, respectively. These indicated deterioration of crystalline quality at a growth temperature between 200 and 220 ℃. However, the RBS suggested that the In atoms were located in interstitial sites along the [110] direction and that the ratio of the interstitial In atoms was estimated to be almost 40% of all In atoms even in the LTG In_0.45Ga_0.55As grown at 220 ℃. X-ray RSM revealed that the LTG In_0.45Ga_0.55As layer was compressively strained, although its lattice constant parallel to the substrate surface was smaller than that of the InP substrate, implying that defect structures are present in the layer. Moreover, the results of XRD measurement and RBS implied transformation of excess As into As precipitates by thermal annealing in both these LTG In_0.45Ga_0.55As and In_0.44Ga_0.56As samples.