Abstract
In0.82Ga0.18As epitaxial layers were grown on InP (100) substrates at 530 °C by a low-pressure metalorganic chemical vapor deposition (LP-MOCVD) technique. The effects of different buffer structures, such as a single buffer layer, compositionally graded buffer layers, and superlattice buffer layers, on the crystalline quality and property were investigated. Double-crystal X-ray diffraction (DC-XRD) measurement, Raman scattering spectrum, and Hall measurements were used to evaluate the crystalline quality and electrical property. Scanning electron microscope (SEM), atomic force microscope (AFM), and transmission electron microscope (TEM) were used to characterize the surface morphology and microstructure, respectively. Compared with the In0.82Ga0.18As epitaxial layer directly grown on an InP substrate, the quality of the sample is not obviously improved by using a single In0.82Ga0.18As buffer layer. By introducing the graded InxGa1−xAs buffer layers, it was found that the dislocation density in the epitaxial layer significantly decreased and the surface quality improved remarkably. In addition, the number of dislocations in the epitaxial layer greatly decreased under the combined action of multi-potential wells and potential barriers by the introduction of a In0.82Ga0.18As/In0.82Al0.18As superlattice buffer. However, the surface subsequently roughened, which may be explained by surface undulation.
Highlights
Inx Ga1−x As (0 < x < 1)—known as ternary compound semiconductor materials—can well cover the infrared radiation of 1~3 μm
For sample B, when the temperature of the reaction chamber was reduced to 450 ◦ C, the 100 nm thick In0.82 Ga0.18 As buffer layer was grown on the InP (100) substrate and the In0.82 Ga0.18 As epitaxial layer was grown when the temperature rose to 530 ◦ C
In0.82Ga0.18As epitaxial layers were grown on InP (100) substrates by a low pressure
Summary
Inx Ga1−x As (0 < x < 1)—known as ternary compound semiconductor materials—can well cover the infrared radiation of 1~3 μm. Because of its excellent characteristics and mature preparation technology, Inx Ga1−x As materials have attracted much research attention and have been widely used in the fields of civil, military, space remote sensing, spectroscopy, and so on [5,6,7,8]. In0.53 Ga0.47 As epitaxial material covering a wavelength of 0.9–1.7 μm is lattice-matched to an InP substrate, which has been developed mainly for fiber communication applications. As there is no lattice-matched substrate for In0.82 Ga0.18 As materials, the large lattice mismatch between the In0.82 Ga0.18 As epitaxial layer and the substrate will result in misfit dislocations or other defects, which will destroy the material quality and further weaken the performance of devices [9]. An additional buffer layer is a Materials 2018, 11, 975; doi:10.3390/ma11060975 www.mdpi.com/journal/materials
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