GaN-based Chemical Sensors and Their On-chip Integration Using Nanowire Networks

本项目主要研究基于氮化镓的高灵敏度化学传感器及其片上集成的关键技术。主要结论如下：(1)综述了Schottky势垒形成的界面模型，讨论了与AlGaN/GaN Schottky势垒相关的关键问题，包括费米能级钉钉、Schottky势垒高度（SBH）和反漏电流。电流输运用薄表面势垒（TSB）模型来解释。通过吸氧过程可以减少泄漏电流。(2)在AlGaN/GaN HEMT晶片上制备的Pd肖特基势垒氢传感器采用吸氧工艺，具有前所未有的高灵敏度。(3)其传感机制是由Pd表面产生的原子氢形成的界面偶极子还原SBH，并扩散到肖特基界面。瞬态反应的限速过程是表面反应。给出了描述稳态和瞬态响应的数学公式。(4)温度越高，AlGaN/GaN氢传感器的灵敏度越高，性能优于其他主要III-V型半导体。(5)在氢传感器二极管中观察到慢瞬变现象，这可以用电子在表面态上随时间连续跳变引起的色散输运来解释。这导致了AlGaN/GaN hemt电流崩溃的新模型。(6)采用电解液/AlGaN栅极结构制备的pH传感hemt具有接近理想的能斯汀响应。讨论了利用该结构实现生物传感器的相关问题。(7)针对传感器的片上集成，提出了一种基于六边形纳米线网络的BDD（二进制决策图）信息处理体系结构。该方案包括基本集成单元、传感器桥、传感器阵列结构、纳米线网络形成的选择性MBE方法以及与片上天线集成的无线通信电路等关键要素。它们的可行性已经得到了证明。少

This project investigates key technologies for realization of GaN-based high-sensitivity chemical sensors and their on-chip integration using nanowires. The main conclusions are as follows: (1) Interface models on Schottky barrier formation are surveyed, and key issues related to AlGaN/GaN Schottky barriers including Fermi level pinning, Schottky barrier height (SBH) and reverse leakage currents are discussed. The current transport is explained by the thin surface barrier (TSB) model. Leakage currents can be reduced by the oxygen gettering process. (2) Pd Schottky barrier hydrogen sensors fabricated on AlGaN/GaN HEMT wafers exhibit unprecedented high sensitivities by applying the oxygen gettering process. (3) Its sensing mechanism is SBH reduction by interface dipole formed by atomic hydrogen which is produced at the Pd surface and diffuses to the Schottky interface. The rate limiting process for transient responses is surface reaction. Mathematical formulas for description of steady-s … More tate and transient response are given. (4) Sensitivity of AlGaN/GaN hydrogen sensors increases at higher temperatures, and they perform better than those by other major III-V semiconductors. (5) Slow transients are observed in hydrogen sensor diodes, and they can be explained by the dispersive transport due to time-continual hopping of electrons through surface states. This has led to a new model of current collapse in AlGaN/GaN HEMTs. (6)pH sensing HEMTs fabricated using an electrolyte/AlGaN gate structure, show nearly ideal Nernstian responses. Issues related to realization of bio-sensors using this structure are discussed. (7) For on-chip integration of sensors, implementation of a BDD (binary decision diagram) information processing architecture on hexagonal nanowire networks has been proposed. The proposal includes key elements such as basic integration unit, a sensor bridge, a sensor array structure, a selective MBE method for nanowire network formation and a wireless communication circuit integrated with an on-chip antenna. Their feasibilities have been proved. Less