MBE Growth And Property Of PIN Structure InAs/GaSb Superlattice

In recent years, the narrow bandgap antimonide based compound semiconductors“0.61nm Ⅲ-Ⅴ group materials” are considered as the promising candidate material forthe third generation infrared detectors. In the field of middle and far infrared detection,typeⅡ InAs/GaSb superlattices with special electronic band structure show the superiorperformance and have broad application prospects. But the growth process of structuralmaterials still faces considerable difficulties and technical challenges. In this paper, wedesign p-i-n structure InAs/GaSb superlattice materials grown on GaAs substrates, andstudy the materials growth technology, structural quality and optical and electricalproperties for the preparation of high-quality materials devices.In this paper, we study the growth of GaSb/GaAs, InAs/GaAs and InAs/GaInSb/GaSb/GaAs heterojunction on GaAs (100) substrates by MBE equipment. Thenwe studied the growth technology of InAs/GaSb superlattice materials based on theoptimized growth process. The optimized growth technologies are as follows:temperature of the buffer layer GaAs and GaSb, the SLs layer InAs/GaSb, the cap layerInAs are600℃,520℃,390℃and380℃respectively. Ⅴ/Ⅲbeam ratio: Sb/Ga=6, As/In=10. We successfully grow p-i-n structure film materials by using Be as a p-typedopant and Si as an n-type dopant. The p-type layer (n-type layer) has different dopingconcentration and thickness, and the intrinsic layer has a different barrier and well layerthickness and cycles.The quality of surface morphology is analyzed by atomic force microscopy (AFM)and scanning electron microscopy (SEM). The samples2-4#,2-2#,2-5#,2-1#and2-3#have gradual increase in the doping concentration, and the2μm x2μm size RMSroughness are1.14nm,1.5nm,1.54nm,1.61nm and2.57nm. It shows that with theincreasing of doping concentration, the material dislocations and defect densityincreases and the surface morphology quality become poorer. This shows that theincreasing thickness of superlattice layer improves the quality of the superlatticestructure. The SEM analysis of2-3#sample show that replacement of the atoms lead tonon-uniform composition and structural quality deterioration because of the increase ofpoint defect density.The quality of material structure is analyzed by double-crystal X-ray diffraction method, and the doping level has greater impact on the p-i-n structure superlattice. Withthe doping concentration increases, the material has less diffraction peak order,widerFWHM and higher dislocation density caused by dopant diffusion in the n-type layer,p-type layer and superlattice layer interface. The increasing thickness of superlatticelayer improves the quality of the superlattice structure. The2-8#sample superlatticecycles is twice that of samples2-9#, so it has more narrow FWHM and lowerdislocation density. The impact of interface layer on short-period superlattice materialsis bigger than long-period superlattice materials.The electrical properties of the material are analyzed by Hall-effect andelectrochemical analysis and we measure Hall mobility, carrier concentration andconductivity type. We study the effects of material defects and superlattice interface onthe carrier concentration and mobility. When the superlattice has the InSb-like interfacecompared with the hybrid interface of InSb-like and GaAs-like, the measured carrierconcentration is lower. Because smaller lattice mismatch of InSb-like interface result infewer defects. We observe that when operating temperature change from the lowtemperature (77K) to room temperature (300K), the superlattice conductivity typeconverse. As the superlattice background conductivity type is p-type, with theincreasing of operating temperature, the electron concentration of the intrinsic excitationis greater than the hole concentration and the electrical conductivity type will conversefrom p-type to n-type.By Raman spectral characteristics of superlattice, we reveal the crystalline qualityof the superlattice materials prepared in the existing process conditions. Combined withthe double-crystal XRD measurement, we analyze the interface type of the superlatticematerials. With uncontrolled growth of interface type, the superlattice interface type isInSb-like, while the poor structural quality of materials show hybrid GaAs-like andInSb-like interface.