High quality (AlGa)0.8In0.2As material with very low threading dislocation density grown on Ge through compositionally graded buffer integrated with strained-layer superlattices

IF 6.3 2区材料科学 Q2 ENERGY & FUELS

Solar Energy Materials and Solar Cells Pub Date : 2025-02-21 DOI:10.1016/j.solmat.2025.113527

Wenyi Yang , Xiaobin Zhang , Xinyi Li , Zimin Chen , Shuyi Zhang , Tingbao Wang , Gang Wang

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引用次数: 0

Abstract

Strained-layer superlattices (SLSs) can be used to filter the threading dislocations (TDs) since the misfit strain can annihilate some TDs and suppress the threading dislocation density (TDD) in the followed films. In this work, the In_0.1Ga_0.9As/GaAs SLSs were introduced into the compositionally graded buffer (CGB) structure aiming to grow In_0.2Ga_0.8As layer with low TDD. Epitaxial wafers with (AlGa)_0.8In_0.2As target layers were grown on Ge substrates by using modified CGB structures integrating various In_0.1Ga_0.9As/GaAs SLSs to replace the bottom In_0.05Ga_0.95As layer of CGB. According to cathodoluminescence tests, lower TDDs were clearly observed in the wafers with SLSs. A very low average TDD of 3.5 × 10⁵ cm⁻² was obtained with the structure integrating 10 periods SLSs with individual layer thickness of 12.5 nm, implying that the critical thickness of In_0.1Ga_0.9As layer in SLSs was close to and below 12.5 nm. This point was also verified by the examinations of cross-sectional transmission electron microscopy. The surface morphologies of epitaxial films were studied by atomic force microscopy, and all samples with SLSs exhibited the lower root mean square surface roughness, indicating the better relaxation of target layers. In_0.2Ga_0.8As single-junction solar cells were prepared on Ge substrates by employing six-step CGB layers with and without 10 periods SLSs. The open-circuit voltage (V_oc) has been significantly improved by integrating 10 periods SLSs. The increase in V_oc is attributed to the ultra-low TDD based on 10-QW SLSs, which can effectively reduce non-radiative recombination rate in solar cell. The bandgap-voltage offset (W_oc = E_g/q - V_oc) value of In_0.2Ga_0.8As cell with 10 periods SLSs is 384 mV, which is only a bit higher than 369 mV of the lattice-matched 1.4-eV In_0.01Ga_0.99As cell grown on Ge (R. R. King et al., Prog. Photovolt., 2011, 19: 797–812), representing excellent crystalline quality of In_0.2Ga_0.8As material.

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通过与应变层超晶格集成的成分梯度缓冲，在Ge上生长出具有极低螺纹位错密度的高质量（AlGa）0.8In0.2As材料

应变层超晶格（SLSs）可以过滤螺纹位错（TDs），因为错配应变可以湮灭部分螺纹位错（TDs）并抑制后续薄膜中的螺纹位错密度（TDD）。本文将In0.1Ga0.9As/GaAs SLSs引入到复合渐变缓冲层（CGB）结构中，旨在生长出低TDD的In0.2Ga0.8As层。采用集成各种In0.1Ga0.9As/GaAs SLSs的改性CGB结构，在Ge衬底上生长出具有（AlGa）0.8In0.2As目标层的外延片，以取代CGB底部的In0.05Ga0.95As层。通过阴极发光测试，可以明显观察到含有sls的晶圆的tdd值较低。采用10周期sls结构，获得了3.5 × 105 cm−2的极低平均TDD，单层厚度为12.5 nm，表明sls中In0.1Ga0.9As层的临界厚度接近或低于12.5 nm。这一点也得到了横断面透射电镜检查的证实。通过原子力显微镜对外延膜表面形貌进行了研究，结果表明，含有SLSs的样品表面均方粗糙度较低，表明目标层有较好的弛豫。采用六步CGB层，在Ge衬底上制备了In0.2Ga0.8As单结太阳能电池。通过集成10周期sls，开路电压（Voc）得到了显著提高。Voc的增加是由于基于10-QW sls的超低TDD，可以有效降低太阳能电池中的非辐射复合率。10周期sls的In0.2Ga0.8As电池的带隙电压偏移（Woc = Eg/q - Voc）值为384 mV，仅略高于Ge （r.r.k King等，Prog.）上生长的晶格匹配的1.4 ev In0.01Ga0.99As电池的369 mV。Photovolt。， 2011, 19: 797-812)，代表了In0.2Ga0.8As材料优异的结晶品质。

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来源期刊

Solar Energy Materials and Solar Cells 工程技术-材料科学：综合

CiteScore

12.60

自引率

11.60%

发文量

513

审稿时长

47 days

期刊介绍： Solar Energy Materials & Solar Cells is intended as a vehicle for the dissemination of research results on materials science and technology related to photovoltaic, photothermal and photoelectrochemical solar energy conversion. Materials science is taken in the broadest possible sense and encompasses physics, chemistry, optics, materials fabrication and analysis for all types of materials.