【摘要】 基于Ⅲ-Ⅴ族半导体的二类超晶格和量子阱材料在中红外光电子器件中有着重要应用。采用分子束外延技术结合界面工程方法,实现了界面应力的精准调控,成功制备了晶格完全匹配的二类超晶格材料。通过校准生长速率等参数,在InAs（001）衬底上外延生长得到了高质量的带间级联激光器材料。该材料表面平整,原子台阶清晰。经原子力显微镜测量,总厚度超过8μm的带间级联激光器结构的表面均方根粗糙度仅为130 pm;光学显微镜测得表面缺陷密度低至10² cm^-2量级;扫描透射电子显微镜观察到二类超晶格和量子阱的异质界面清晰明锐。基于以上高质量的二类超晶格和量子阱材料,InAs基带间级联激光器的性能取得了显著突破:在300 K时实现了最短激射波长（4.02μm）,且具有最低的阈值电流密度232 A/cm²;在长波长（8.22μm）时,获得了275K的最高工作温度。更多还原

【Abstract】 Objective The optoelectronic devices based on type-Ⅱ quantum wells（QWs） and superlattices（SLs） have important applications in the field of mid-infrared（mid-IR） technology.Type-Ⅱ QWs and SLs based on Ⅲ-Ⅴ semiconductors are a type of artificial microstructure materials designed through band engineering.It can be formed by alternating growth of InAs,GaSb,AlSb,and their multicomponent alloys to form periodic structures.The type-Ⅱ QWs and SLs can be grown using the molecular beam epitaxy（MBE） technique,which produces a uniform material over a large area.The corresponding bandgap covers the infrared spectrum of2.7-30 μm,offering low Auger recombination efficiency and high quantum efficiency.The optoelectronic devices based on type-ⅡQWs and SLs,such as interband cascade lasers,quantum cascade lasers,infrared detectors,and solar cells,have important applications in military and civilian fields,including infrared detection,industrial detection,gas sensing,healthcare.However,the type-Ⅱ QWs and SLs used in mid-infrared lasers and detector devices usually contain thousands of heterointerfaces that are susceptible to element mixing and diffusion.It can lead to lattice distortion and stress generation.Therefore,achieving high-quality epitaxial growth in type-Ⅱ QWs and SLs faces significant challenges.Methods Type-Ⅱ QWs and SLs are epitaxially grown by a solid-source MBE system,which is equipped with valved arsenic and antimony crackers.The crystalline surface quality of the as-grown layer is monitored in-situ by reflection high energy electron diffraction（RHEED） in real time.Interband cascade laser（ICL） devices are fabricated from the two wafers by wet etching and contact photolithography.They are mounted epi-side up on copper heat sinks with uncoated facets for laser testing.The Fourier transform infrared spectrometer is used for recording the lasing spectra.In order to reduce the interfacial mixing of type-Ⅱ QWs and SLs materials and balance the strain,it is particularly important to calibrate the growth rate and lattice matching.Here,the interfacial strain is controlled by interface engineering in the MBE growth,resulting in perfectly lattice-matched type-Ⅱ QWs and SLs.Together with the rigorous calibration on the growth rates and doping concentrations,high-quality ICL structures composed of a large number of type-Ⅱ QWs and SLs grown on InAs（001） substrates are successfully demonstrated.Results and Discussions First,the crystal lattice matching,growth rate and doping concentration of type-Ⅱ QWs and SLs are calibrated.The lattice matching of type-Ⅱ QWs and SLs is calibrated by inserting an AlAs interface.As shown in Fig.1,the cascade superlattice in the interband cascade laser achieves good lattice matching with the InAs substrate.The growth rates of InAs,GaSb,and AlSb are calibrated using RHEED oscillation,and the carrier doping concentration is calibrated using the Hall effect.Then,we apply the growth and calibrated parameters to the interband cascade laser structure.As shown in Fig.3,the interband cascade laser structure is fully strained to the InAs substrate,reducing the defects generated during film relaxation.The as-grown surface defects density is as low as 102/cm².The atomic force microscope reveals a series of clear,regular atomic terraces.These atomic terraces are about 0.33 nm high,which corresponds to one monolayer InAs,and the root mean square roughness in the 3 μm × 3 μm scanning area is only 0.13 nm.To see the heterointerfaces more clearly,cross-sectional scanning transmission electron microscope（STEM） shows the atomic-level flatness of type-Ⅱ QWs and SLs interfaces（including InAs/AlSb and InAs/GaInSb）.Finally,the high quality interband cascade laser materials are fabricated into laser devices.Figure 4 shows that we obtain a series of high performance interband cascade lasers.At the wavelengths of 4 μm and 8 μm,the highest operating temperature and the low threshold current density are achieved in our works.Conclusions In this work,the interface engineering is used to precisely control interface strain,resulting in the type-Ⅱ QWs and SLs with perfect lattice matching.By using molecular beam epitaxy technology,high-quality interband cascade laser structures are epitaxially grown on the InAs（001） substrates,with growth parameters strictly calibrated such as growth temperature,growth rate,and doping concentration.The surface measured by atomic force microscope yields a root-mean-square roughness of 130 pm on an ICL structure with thickness more than 8 μm.Meanwhile,the defect density under optical microscope is in the level as low as10² cm^-2.The cross-sectional STEM image clearly shows the sharp hetero-interfaces of type-Ⅱ SLs.Ultimately,breakthroughs on the device performance are demonstrated for InAs-based ICLs.For example,the shortest lasing wavelength of 4.02 μm in pulsed operation with the lowest threshold current density of 232 A/cm² is achieved at 300 K.And the highest operating temperature of 275 K is also achieved in an ICL lasing in the long wavelength infrared region（8.22 μm）.These results demonstrate that improving the materials quality of type-Ⅱ superlattices can enhance the performance of infrared optoelectronic devices.更多还原