Most current techniques for analyzing amino acids require substantial instrumentation and significant sample preprocessing. In this study, we designed, fabricated, and tested a scalable diode-based microdevice that allows for direct sensing of amino acids. The device is based on modulation-doped GaAs heterostructure with a Schottky contact on one side. The relatively high mobility and relatively small dielectric constant of GaAs are naturally helpful in this problem. We also paid attention to a proper etching procedure allowing for substantial modification of the surface properties, thereby further boosting the sensing performance. Transport data (I-V, differential conductance) are presented for three qualitatively different classes of amino acids (i.e., nonpolar with aliphatic R-group, polar uncharged R-group, and charged R-group) with glycine, cysteine, and histidine as specific examples, respectively. The conductance for the GaAs-amino acid interface measured using a scanning tunneling microscope (STM) was previously reported to have distinct spectral features. In this paper, we show that measuring the differential conductance of a GaAs diode, whose surface is in direct contact with an aqueous solution of amino acid, is a simple methodology to access useful information, previously available only through sophisticated and equipment-demanding STM and molecular electronics approaches. Density functional theory calculations were used to examine which adsorption processes were likely responsible for the observed surface conductance modification. Last, in future and ongoing work, we illustrate how it might be possible to employ standard multivariate data analysis techniques to reliably identify distinct (95 %) single amino acid specific features in near-ambient differential conductance data.

中文翻译：

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使用调制掺杂和表面纳米工程 GaAs 肖特基 PIN 二极管检测某些氨基酸

用于分析氨基酸的大多数当前技术需要大量仪器和重要的样品预处理。在这项研究中，我们设计、制造并测试了一种可扩展的基于二极管的微型设备，可以直接检测氨基酸。该器件基于调制掺杂的 GaAs 异质结构，一侧具有肖特基接触。GaAs 相对高的迁移率和相对小的介电常数自然有助于解决这个问题。我们还注意适当的蚀刻程序，允许对表面特性进行实质性修改，从而进一步提高传感性能。传输数据（IV，微分电导）显示为三种性质不同的氨基酸类别（即具有脂肪族 R 基团的非极性、极性不带电 R 基团和带电 R 基团）与甘氨酸，分别以半胱氨酸和组氨酸为例。之前报道过使用扫描隧道显微镜 (STM) 测量的 GaAs-氨基酸界面的电导具有不同的光谱特征。在本文中，我们展示了测量 GaAs 二极管的微分电导，其表面与氨基酸水溶液直接接触，是一种获取有用信息的简单方法，以前只能通过复杂且设备要求高的 STM 和分子电子学方法。密度泛函理论计算用于检查哪些吸附过程可能导致观察到的表面电导改性。最后，在未来和正在进行的工作中，