氢致金刚石表面载流子输运沟道形成与稳定机制研究

Hydrogen terminated diamond becomes one of most promising semiconductors in broadband and high-capacity wireless communication field due to the stable P- type conductive channel beneath the surface, such as sheet resistance 104-106 Ω/□. However, in the conductive channel, the carrier mobility is much lower than the theoretical value of diamond and moreover, carrier transport behavior is extremely vulnerable to environment. To optimize the surface conductivity and fabricate extremely high frequency and high power electronic device based on H-terminated diamond, it is crucial to study the formation and stabilization mechanism of the carrier channel transport. This project aims to explore the inherent driving force for hydrogen induced conductive channel through investigating carrier transport in response to the atmospheric environment, based on band structure of H-terminated diamond. Combining with the principle of charge transfer induced by potential barrier, surface and interface electron transfer model was built; according to the law of carrier transport, the carrier scattering model related to diamond surface defects was set up and measures to enhance the carrier migration was proposed; The inner modulation mechanism of the passivation layer on H-terminated diamond surface was revealed by understanding the stabilization effect of passivation layer/H-terminated diamond based on the interfacial polarization theory. This study will lay the theoretical foundation for the development of reliable devices operating at extremely high frequency and high power mode.

氢终结金刚石由于在近表面形成稳定的P型导电沟道，如方块电阻104-106 Ω/□，成为未来宽频带、超大容量无线通讯领域最有前景的半导体选择。然而该导电沟道中载流子迁移率远低于金刚石的理论值，且载流子输运极易受到环境变化的影响，为此针对沟道中载流子输运形成及稳定化的研究，对优化半导体性质、构建极高频超大功率电子器件至关重要。本项目基于氢原子终结金刚石能带结构出发，从表面导电沟道中载流子输运对大气环境的响应入手，探索氢致金刚石表面P型导电沟道的内在驱动力。本项目拟结合势垒激发电荷转移原理，构建氢终结金刚石表界面电子转移模型；基于表面沟道载流子输运规律，建立与金刚石表面缺陷相关的载流子散射模型，提出利于载流子迁移的优化调控措施；依据钝化层对金刚石表面导电沟道的稳定化规律，基于界面极化理论，揭示钝化层对导电沟道的内在调制机理。本研究将为指导开发可靠的极高频超大功率电子器件奠定理论基础。

针对当前氢终结金刚石表面导电沟道存在表面性质不稳定、导电沟道迁移率低以及器件耐压不足等问题，依照项目设定的研究目标系统开展了氢终结金刚石表面 P 型导电沟道形成的实验研究、氢终结金刚石的能带结构图谱绘制、氢终结金刚石表面钝化及相关器件研制等研究内容，最终揭示了氢终结金刚石表面载流子输运沟道形成的内在驱动力，建立了金刚石表面缺陷相关的载流子散射模型，确立了合适的钝化层体系。研究表明氢终结金刚石表面导电沟道源于氢终结金刚石表面负的电子亲和势与大气电化学环境共同作用的界面电荷转移机制，二者是氢终结金刚石表面导电的充分必要条件。氢终结金刚石表面导电沟道中载流子迁移率与表面粗糙度的平方成反比关系,同时受金刚石体表杂质散射影响。通过对氢终结金刚石表面粗糙度的修复与外延层的净化，能够显著提高表面导电沟道的载流子迁移率。原子层沉积的Al2O3膜对于氢终结金刚石表面钝化效果良好，界面的缺陷密度在1011-1012cm-2eV-1量级，同时可以在200℃以上仍然稳定。基于Al2O3钝化的氢终结金刚石电子器件显示出良好的耐压特性。钝化层的选择不仅需要其本身的能带结构与氢终结金刚石能够匹配，而且还需要在实际制备过程中尽可能少的引入界面缺陷，从而实现导电沟道的稳定与性能提高。本项目的实施将为氢终结金刚石表面钝化层的筛选与优化、金刚石基电子器件研究打下基础。