Photonic sensing platform based on photocorrosion of III-V semiconductor microstructures

该计划旨在探索III-V半导体微结构的电化学性质和光学性质，这些微结构包括异质结构、量子阱(QW)或量子点(QD)，用于检测固定在此类微结构表面附近的带电生物分子。光致发光(PL)效应对半导体表面附近的能带弯曲以及表面态的密度和性质的改变的敏感性是化学和生物传感研究的一个众所周知的效应。我们最近发现，半导体异质结构的光腐蚀，如果在由半导体周围电解液的光激发功率、平均光子通量和刻蚀功率决定的优化条件下发生，可能成为发生在距离半导体表面不到40 nm的距离处发生的电化学反应或生化反应的指纹。利用光腐蚀效应来监测表面反应，为基于光致发光的表面固定生物分子的检测增加了一个吸引人的维度。我们利用被这种异质结构掩埋的一层GaAs层的光致发光，观察到了一堆外延生长的GaAs/AlGaAs异质结的解离过程。原位解决1 nm薄层的光腐蚀问题的能力表明，这种方法可以为监测涉及低浓度带电生物分子的反应提供有吸引力的条件。这种“反向分子束外延”的另一个潜在优势与半导体的光腐蚀暴露表面的原位生物功能化有关。这可以创造优化的条件，例如，生长高质量的自组装单分子膜(SAM)，否则需要应用昂贵的真空或高纯度环境控制设备。对十(10)个异质结的光腐蚀实验结果表明，可以设计出具有更多异质结的器件，用于生物功能化和对其附近发生的生化反应的顺序监测。基于光腐蚀的诊断的创新特征，以及这种方法可能导致一类新的(生物)传感器和监测涉及带电分子的表面反应的技术，为本文档中描述的计划奠定了基础。该计划的核心是开发一幅带电分子在液体环境中与不同半导体微结构表面相互作用的定量(或准定量)图像。这将导致一系列器件的构建，这些器件具有堆叠的异质结构，QW或QD经过优化，可快速且具有极高吸引力的成本产生灵敏的诊断。

This program aims at exploring both electrochemical and optical properties of III-V semiconductor microstructures comprising heterostructures, quantum wells (QW) or quantum dots (QD) for detection of electrically charged biomolecules immobilized in the vicinity of the surface of such microstructures. The sensitivity of the photoluminescence (PL) effect to band bending of a semiconductor near its surface and modification of both density and nature of the surface states is a well known effect investigated for chemical and biological sensing. We have discovered recently that photocorrosion of a semiconductor heterostructure, if induced under optimized conditions determined by light excitation power, average photon fluence and etching power of a semiconductor surrounding electrolyte, could become a fingerprint of the electrochemical or biochemical reactions taking place at distances, typically, less than 40 nm from the semiconductor surface. The employment of the photocorrosion effect for monitoring surface reactions adds an attractive dimension to the PL-based detection of surface-immobilized biomolecules. We have observed a dissociation process of a stack of epitaxially-grown GaAs/AlGaAs heterojunctions, by employing PL of a GaAs layer buried by such heterostructures. The ability to resolve in situ the photocorrosion of a 1 nm thin GaAs layer has suggested that this approach could offer conditions attractive for monitoring the reactions involving low concentrations of electrically charged biomolecules. Another potential advantage of this "reverse molecular beam epitaxy" concerns in situ biofunctionalization of the photocorrosion-revealed surface of a semiconductor. This could create conditions optimized, e.g., for the grow of high-quality self-assembled monolayers (SAM) that otherwise requires the application of expensive vacuum or high-purity environment controlling equipment. The results of the photocorrosion experiment with a stack of ten (10) GaAs/AlGaAs heterojunctions have suggested that devices with even larger number of heterojunctions could be designed for biofunctionalization and sequential monitoring of biochemical reactions taking place in their vicinity. The innovative character of the photocorrosion-based diagnostics, and the potential of this approach to lead to a new class of (bio)sensors and techniques to monitor surface reactions involving electrically charged molecules, have created the base of a program described in this document. At the center of the program is the development of a quantitative (or a quasi-quantitative) picture of charged molecules interacting in a liquid environment with surfaces of different semiconductor microstructures. This will lead to the construction of a family of devices with stacks of heterostructures, QW or QD optimized for yielding a sensitive diagnostics, rapidly and at a highly attractive cost.