科研之友
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摘要
The performance of type-II superlattice(T2 SL) long-wavelength infrared devices is limited by crystalline quality of T2 SLs. We optimize the process of growing molecular beam epitaxy deposition T2 SL epi-layers on Ga Sb(100)to improve the material properties. Samples with identical structure but diverse In/Ga beam-equivalent pressure(BEP) ratio are studied by various methods, including high-resolution x-ray diffraction, atomic force microscopy and high-resolution transmission electron microscopy. We find that appropriately increasing the In/Ga BEP ratio contributes to improving the quality of T2 SLs, but too large In BEP will much more easily cause a local strain,which can lead to more In Sb islands in the In Sb interfaces. The In Sb islands melt in the In Sb interfaces caused by the change of chemical potential of In atoms may result in the "nail" defects covering the whole T2 SLs, especially the interfaces of Ga Sb-on-In As. When the In/Ga BEP ratio is about 1, the T2 SL material possesses a lower full width at half maximum of +1 first-order satellite peak, much smoother surface and excellently larger area uniformity.
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