Abstract High-efficiency semiconductor lasers and light-emitting diodes operating in the 3–5 μm mid-infrared (mid-IR) spectral range are currently of great demand for a wide variety of applications, in particular, gas sensing, noninvasive medical tests, IR spectroscopy etc. III-V compounds with a lattice constant of about 6.1 A are traditionally used for this spectral range. The attractive idea to fabricate such emitters on GaAs substrates by using In(Ga,Al)As compounds is restricted by either the minimum operating wavelength of ∼8 μm in case of pseudomorphic AlGaAs-based quantum cascade lasers or requires utilization of thick metamorphic InxAl1-xAs buffer layers (MBLs) playing a key role in reducing the density of threading dislocations (TDs) in an active region, which otherwise result in a strong decay of the quantum efficiency of such mid-IR emitters. In this review we present the results of careful investigations of employing the convex-graded InxAl1-xAs MBLs for fabrication by molecular beam epitaxy on GaAs (001) substrates of In(Ga,Al)As heterostructures with a combined type-II/type-I InSb/InAs/InGaAs quantum well (QW) for efficient mid-IR emitters (3–3.6 μm). The issues of strain relaxation, elastic stress balance, efficiency of radiative and non-radiative recombination at T = 10–300 K are discussed in relation to molecular beam epitaxy (MBE) growth conditions and designs of the structures. A wide complex of techniques including in-situ reflection high-energy electron diffraction, atomic force microscopy (AFM), scanning and transmission electron microscopies, X-ray diffractometry, reciprocal space mapping, selective area electron diffraction, as well as photoluminescence (PL) and Fourier-transformed infrared spectroscopy was used to study in detail structural and optical properties of the metamorphic QW structures. Optimization of the growth conditions (the substrate temperature, the As4/III ratio) and elastic strain profiles governed by variation of an inverse step in the In content profile between the MBL and the InAlAs virtual substrate results in decrease in the TD density (down to 3 × 107 cm−2), increase of the thickness of the low-TD-density near-surface MBL region to 250–300 nm, the extremely low surface roughness with the RMS value of 1.6–2.4 nm, measured by AFM, as well as rather high 3.5 μm-PL intensity at temperatures up to 300 K in such structures. The obtained results indicate that the metamorphic InSb/In(Ga,Al)As QW heterostructures of proper design, grown under the optimum MBE conditions, are very promising for fabricating the efficient mid-IR emitters on a GaAs platform.

中文翻译：

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在 GaAs 上生长的变质 InAs(Sb)/InGaAs/InAlAs 纳米异质结构用于高效的中红外发射器

摘要 目前，在 3-5 μm 中红外 (mid-IR) 光谱范围内工作的高效半导体激光器和发光二极管在广泛的应用中有着巨大的需求，特别是气体传感、无创医学测试、 IR 光谱等。具有约 6.1 A 晶格常数的 III-V 化合物传统上用于该光谱范围。通过使用 In(Ga,Al)As 化合物在 GaAs 衬底上制造此类发射器的有吸引力的想法受到基于伪晶 AlGaAs 的量子级联激光器的 8 μm 的最小工作波长的限制，或者需要利用厚变质 InxAl1- x由于缓冲层 (MBL) 在降低有源区中的穿透位错 (TD) 密度方面发挥着关键作用，否则会导致这种中红外发射器的量子效率强烈衰减。在这篇综述中，我们展示了使用凸梯度 InxAl1-xAs MBLs 通过分子束外延在 In(Ga,Al)As 异质结构衬底上通过分子束外延制造的结果I InSb/InAs/InGaAs 量子阱 (QW)，用于高效的中红外发射器（3–3.6 μm）。讨论了与分子束外延 (MBE) 生长条件和结构设计相关的应变松弛、弹性应力平衡、T = 10-300 K 时辐射和非辐射复合效率的问题。包括原位反射高能电子衍射、原子力显微镜 (AFM)、扫描和透射电子显微镜、X 射线衍射、倒易空间映射、选择性区域电子衍射以及光致发光 (PL) 和傅里叶变换红外光谱用于详细研究变质 QW 结构的结构和光学特性。生长条件（衬底温度、As4/III 比率）和弹性应变分布的优化由 MBL 和 InAlAs 虚拟衬底之间 In 含量分布中的逆阶变化控制，导致 TD 密度降低（低至3 × 107 cm−2)，低 TD 密度近表面 MBL 区域的厚度增加到 250-300 nm，极低的表面粗糙度，RMS 值为 1.6-2.4 nm，由 AFM 测量，如在这种结构中，在高达 300 K 的温度下具有相当高的 3.5 μm-PL 强度。所得结果表明变质 InSb/In(Ga,