Walter Schottky Institut, Physik Department, and Center of Nanotechnology and Nanomaterials, Technische Universität München , Am Coulombwall 4, Garching, 85748, Germany.
Nano Lett. 2013;13(12):6070-7. doi: 10.1021/nl403341x. Epub 2013 Nov 26.
Utilizing narrow band gap nanowire (NW) materials to extend nanophotonic applications to the mid-infrared spectral region (>2-3 μm) is highly attractive, however, progress has been seriously hampered due to their poor radiative efficiencies arising from nonradiative surface and Auger recombination. Here, we demonstrate up to ~ 10(2) times enhancements of the emission intensities from InAs NWs by growing an InAsP shell to produce core-shell NWs. By systematically varying the thickness and phosphorus (P)-content of the InAsP shell, we demonstrate the ability to further tune the emission energy via large strain-induced peak shifts that already exceed >100 meV at comparatively low fractional P-contents. Increasing the P-content is found to give rise to additional line width broadening due to asymmetric shell growth generated by a unique transition from {110}- to {112}-sidewall growth as confirmed by cross-sectional scanning transmission electron microscopy. The results also elucidate the detrimental effects of plastic strain relaxation on the emission characteristics, particularly in core-shell structures with very high P-content and shell thickness. Overall, our findings highlight that enhanced mid-infrared emission efficiencies with effective carrier confinement and suppression of nonradiative recombination are highly sensitive to the quality of the InAs-InAsP core-shell interface.
利用窄带隙纳米线 (NW) 材料将纳米光子学应用扩展到中红外光谱区域（>2-3 μm）非常有吸引力，然而，由于其非辐射表面和俄歇复合导致的辐射效率低下，进展受到了严重阻碍。在这里，我们通过生长 InAsP 壳来制备核壳 NW，证明了 InAs NW 发射强度可提高高达 ~ 10(2) 倍。通过系统地改变 InAsP 壳的厚度和磷 (P) 含量，我们展示了通过大应变诱导的峰位移进一步调谐发射能的能力，这种峰位移在相对较低的分数 P 含量下已经超过了 >100 meV。增加 P 含量会由于独特的从 {110}-到 {112}-侧壁生长的转变而导致壳生长不对称，从而引起额外的线宽展宽，这一点通过横截面扫描透射电子显微镜得到了证实。研究结果还阐明了应变弛豫对发射特性的有害影响，特别是在具有非常高的 P 含量和壳厚的核壳结构中。总的来说，我们的发现强调了具有有效载流子限制和抑制非辐射复合的增强型中红外发射效率对 InAs-InAsP 核壳界面质量高度敏感。
