Growth And Characterization Of InAsP/InAsSb And InP/InGaAs Superlattices By MOCVD

Arsenic-phosphorus system materials have great advantages in electron mobility,and different material combinations broaden the material family.The arsenicphosphorus system materials containing antimony have been significantly used in infrared detection,involving military and some civil fields.Arsenic-phosphorus system superlattice is very suitable for high-speed devices and lasers with high mobility.In terms of material growth,metal-organic chemical vapor deposition(MOCVD)and molecular beam epitaxy(MBE)are the two main growth techniques.Compared with the latter,MOCVD attracts a lot of concentration with its advantages of capability of high-volume low-cost production and suitability for commercial production.However,there are also many challenges to overcome in growth materials by MOCVD.Therefore,this paper mainly introduces the optimal growth of mid-wave InAsP/InAsSb superlattices and short-wave InP/InGaAs superlattices by MOCVD growth technology and utilize of a series of characterization methods to test the material quality.The main work include the following two aspects:1."Ga-free" strain-balanced InAsP/InAsSb superlattices grown on InAs substrate by MOCVD was proposed and implemented to explore its feasibility as an infrared absorption material.First,the band gaps of InAsP/InAsSb superlattices were calculated by k-p method and it was found that their cut-off wavelengths cover mid-wavelength infrared to long wave infrared region.Then InAs0.8P0.2/InAs0.7Sb0.3 superlattices was chosen and grown on InAs substrate by MOCVD.XRD measurement shows that the lattice mismatch between the InAs substrate peak and 0th order satellite peak of superlattices is only 61 arcsec,indicating strain balance condition is achieved.AFM test for surface morphology shows its root mean square roughness is only 0.4 nm for 5×5 μm2 regions.The low-temperature PL spectra shows strong superlattice emission with peak located around 3.3μm,which is closed to the design value.All the results indicate the feasibility and practicality of strain balanced InAsP/InAsSb superlattices grown by MOCVD for infrared detection.2.Choose to grow a InP/InGaAs short-wave superlattices on InP substrates.Firstly,the InGaAs layer was grown on the InP substrate,and the XRD test indicated In components of InGaAs and growth rates of 0.533 and 0.21 nm/s,respectively.Later,the growth conditions of interface 1(InP to InGaAs)were not changed,and only the AsH3 protection time T1 and PH3 preflow time T2 at interface 2(InGaAs to InP)were changed to grow three(20 nm)InP/(10 nm)In0.53Ga0.47As superlattices.Microscope and AFM observed smooth surface and step flow surface morphology,respectively;XRD measurement shows there are-67 arcsec,-17 arcsec and-114 arcsec lattice mismatch between superlattices and substrate,and the corresponding negative primary peak FWHM are 57 arcsec,54 arcsec and 46 arcsec as well as cycle thickness of 30.58nm,30.4 nm and 30.68nm,respectively,which are very closed to the design value,The HADDF image of the sample measured by STEM clearly shows a complete superlattices period,with a period thickness of 31.17 nm,31.83 nm and 31.14 nm,respectively.After analyzing strain at the material interface by GPA,the possible components of interface 1 and 2 calculated by Vegard’s law should be InAsP and InGaAsP,respectively.The EDS test images of the sample show that the atomic fraction presents stable periodic changes,and the interface thickness is calculated based on atomic fraction changes of P and As,respectively.By contrast,the superlattice sample without P preflow has the narrowest interface,and we believe that the P-As exchange is reduced under this condition,which helps to facilitate the formation of the mutant interface.