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

该项目研究实现基于 GaN 的高灵敏度化学传感器及其使用纳米线的片上集成的关键技术。主要结论如下：（1）研究了肖特基势垒形成的界面模型，讨论了AlGaN/GaN肖特基势垒的费米能级钉扎、肖特基势垒高度（SBH）和反向漏电流等关键问题。电流传输由薄表面势垒（TSB）模型解释。通过吸氧工艺可以减少漏电流。 (2) 在 AlGaN/GaN HEMT 晶圆上制造的 Pd 肖特基势垒氢传感器通过应用吸氧工艺表现出前所未有的高灵敏度。 (3)其传感机制是Pd表面产生的原子氢扩散到肖特基界面形成的界面偶极子还原SBH。瞬态响应的速率限制过程是表面反应。给出了描述稳态和瞬态响应的数学公式。 (4) AlGaN/GaN氢传感器的灵敏度在较高温度下提高，并且其性能优于其他主要III-V族半导体。 (5) 在氢传感器二极管中观察到缓慢的瞬变，这可以通过电子通过表面态的时间连续跳跃引起的色散传输来解释。这导致了 AlGaN/GaN HEMT 中电流崩塌的新模型。 (6) 使用电解质/AlGaN 栅极结构制造的 pH 传感 HEMT 显示出近乎理想的能斯特响应。讨论了与使用这种结构实现生物传感器相关的问题。 (7)对于传感器的片上集成，提出了在六边形纳米线网络上实现BDD（二元决策图）信息处理架构。该提案包括基本集成单元、传感器桥、传感器阵列结构、用于纳米线网络形成的选择性MBE方法以及集成片上天线的无线通信电路等关键元件。它们的可行性已被证明。较少的

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