镓辅助热氧化生长ZnO/ZnGa2O4复合层及其发光机理研究

The non-Ohmic contact between metal electrode and ZnO due to the formation of Schottky barrier would worsen the luminescent properties of ZnO-based LEDs (ZnO-LEDs). In addition, it is still difficult to obtain an efficient and stable p-type ZnO. Therefore, one of the effective solutions to these problems is to construct a Schottky ZnO-LED based on an n-type ZnO wherein the carrier injected light emission could easily occur at a metal-semiconductor junction. However, the operation voltage of Schottky ZnO-LEDs is generally high. Therefore, a new solution is proposed to construct ZnO-LEDs with a low operation voltage by using ZnO/ZnGa2O4 composite layers. In this research, the ZnO/ZnGa2O4 composite layers will be grown by the thermal oxidation with gallium. ZnS films grown by magnetron sputtering technique and purchased ZnS bulks will serve as the source substrates. The evolution behavior of the microstructures in consideration of the growth conditions will be investigated and the luminescent properties with related impact factors will be analyzed. The relationship between the microstructures and luminescent properties of the ZnO/ZnGa2O4 composite layers will be established. The growth mechanism as well as the luminescent mechanism of the ZnO/ZnGa2O4 composite layers will be clarified. The construction principle of ZnO-LEDs with a low operation voltage based on the ZnO/ZnGa2O4 composite layers will be revealed. This research would suggest the possibility of ZnO-LEDs with a low operation voltage constructed by a simple method.

金属电极与ZnO非欧姆接触形成的肖特基势垒会影响ZnO-LED的发光性能，且高效、稳定的p-ZnO仍不易获得。基于n-ZnO构筑肖特基ZnO-LED是解决这一问题的有效途径，可在金属-半导体界面实现载流子注入发光。针对肖特基ZnO-LED工作电压较高的问题，本项目提出基于ZnO/ZnGa2O4复合层结构构筑低电压ZnO-LED的解决途径。选择ZnS块体和磁控溅射生长的ZnS薄膜作为源基板，采用镓辅助热氧化生长ZnO/ZnGa2O4复合层。考察ZnO/ZnGa2O4复合层微观结构随生长条件的演变规律，分析ZnO/ZnGa2O4复合层的发光特性及其影响因素，建立ZnO/ZnGa2O4复合层微观结构特征与发光特性的关系，阐明ZnO/ZnGa2O4复合层的生长机制和发光机理，揭示基于ZnO/ZnGa2O4复合层结构的低电压ZnO-LED的构筑原理，为通过简单方法构筑低电压ZnO-LED提供新思路。

选择ZnS块体和薄膜为源基板，通过镓辅助热氧化生长了ZnO/ZnGa2O4复合层，重点研究了生长条件对复合层微观结构和发光性能的影响规律，阐明了复合层的生长机制和发光机理。取得的主要研究成果有：1）在较宽的生长条件下（热氧化温度700-900℃，热氧化时间1-24h）实现了复合层生长，构筑的的肖特基发光二极管具有低电压发光特性（2.5-9.8V），是在正偏压驱动下的少数载流子高效注入发光。2）ZnS源基板对于复合层结构具有重要影响，热氧化ZnS块体生长的复合层结构为表面ZnO薄膜覆盖下面ZnGa2O4层，而热氧化ZnS薄膜生长的复合层结构为ZnGa2O4分散在ZnO薄膜中。复合层生长过程都是温度控制的扩散-反应过程，并且在生长过程中有Ga掺入ZnO薄膜，进而影响了微观结构和发光性能，而这与生长条件密切相关。3）Ga掺入ZnO降低了可见/紫外PL峰强度比，热氧化温度显著影响了紫外发光峰的D0X/DAP强度比和载流子寿命，并利用TRPL技术详细分析了载流子复合过程。4）通过对比不同生长条件下的可见/紫外PL峰强度比、Ga含量、空位氧/晶格氧XPS峰强度比、Zn/O比等，详细分析了生长条件对掺杂状态和缺陷类型的影响，建立了复合层微观结构和发光性能的关系，阐明了复合层的发光机理。总之，本项目完成的研究内容为进一步研究复合层的缺陷调控和光电性能提供了实验依据，对于低电压发光二极管的构筑研究具有参考价值。