GaN纳米线的PECVD制备及其性能研究

摘要

摘要

第三代半导体材料氮化镓(GaN)是一种直接带隙宽禁带半导体，具有较高的电子饱和速度及载流子迁移率、高热导率、出色的击穿强度和耐高温能力、较好的抗腐蚀和抗辐射能力等优异性质。GaN纳米线作为低维半导体纳米结构，拥有独特的尺寸特征和性能优势，在纳米光电器件和高功率纳米电子器件等领域具有潜在应用价值，如紫外发光二极管，场效应晶体管，光电探测器，纳米激光器和生化传感器等。

在前期研究基础上，提出了一种简单，廉价且环保的制备GaN纳米线的方法，进一步研究了纳米线的调控生长、光电性能和电催化性能，主要研究进展如下：

1. 利用低成本的等离子体增强化学系气相沉积系统(PECVD)，以各向同性石墨为衬底，金属Ga为Ga源，不需要任何催化剂，通过Ga原子与N等离子体直接反应制备出了直径范围为90-200 nm，长度范围为4-20 μm的GaN纳米线。通过对所制备的纳米线的形貌、结构和成分的表征，表明所制备的产物为多晶结构的六方纤锌矿GaN纳米线，其形貌呈现为三维金字塔岛状结构。进一步系统研究了生长温度、射频功率、生长时间、气体流量等工艺参数对所制备GaN 纳米线的形貌和性能的影响。此外，通过表征分析和系列的对比试验，提出了无催化剂制备GaN纳米线的形核和生长的模型。

2. 采用上述方法所制备GaN纳米线，系统研究了其光致发光(PL)和场发射性能。结果表明，所制备的GaN纳米线具有良好的PL性能，纳米线的形貌结构对其PL性能产生显著的影响。所制备GaN纳米线也具有优异的场发射性能，其开启电压低至4-6 V/μm，纳米线结构形貌对其场发射性能有一定的影响，进一步研究了结构对其场发射性能的影响机制。

3.将采用上述方法所制备GaN纳米线进行了电催化性能的研究。研究表明无需修饰和负载的情况下，多晶GaN纳米线即表现出优秀的电催化析氢性能，其析氢电位为280 mV，这可能源于多晶GaN纳米线结构具有丰富的缺陷与突起结构，能够在电解水的催化过程中提供大量的活性位点，有利于电解液的扩散和气体的产生与脱附。所制备具有良好的电催化性能的多晶GaN纳米线，将有望取代传统贵金属电催化材料，实现低成本高性能电催化器件。

北京工业大学工学硕士学位论文

关键词：氮化镓(GaN)；纳米线；无催化剂；光致发光(PL)；场发射；电催化

Abstract

Abstract

Gallium nitride (GaN), a third-generation semiconductor material, is a direct bandgap wide bandgap semiconductor with excellent properties, such as high electron saturation speed, carrier mobility, high thermal conductivity, and meanwhile owning excellent performance in breakdown strength and high temperature resistance, corrosion resistance and radiation resistance. GaN nanowires, as low-dimensional semiconductor nanostructures, have unique characteristics of size and performance advantages, and have potential applications in nanooptoelectronic devices and high-power nanoelectronic devices, including ultraviolet light-emitting diodes, field effect transistors, photodetectors, nanolasers and biochemical sensors since its unique dimensional and performance advantages.

On the basis of previous studies, this paper proposes a simple, inexpensive and environmentally friendly method in preparing GaN nanowires, and further studies the regulation growth, photoelectric properties and electrocatalysis applications of the nanowires. The main research progresses are as follows:

1. Using a low-cost plasma enhanced chemical vapor deposition system (PECVD) with isotropic graphite as the substrate and metal gallium as the gallium source without any catalyst. The GaN nanowires with a diameter ranging from 90 to 200 nm and a length ranging from 4 to 20 μm were prepared by direct reaction Ga atoms and N plasma. The morphology, structure and composition of the prepared nanowires were characterized, which shows that the prepared products are hexagonal wurtzite GaN nanowires that have polycrystalline structures, and they have the three-dimensional pyramid island structure. Further, the effects of process parameters (growth temperature, RF power, growth time, gas flow) on the morphology and properties of the prepared nanowires were also investigated. In addition, through a series of experiments and characterization analysis, we proposed a model for nucleation and growth of GaN nanowires without catalysts. This method will provide a novel alternative to low-cost, large-scale production of GaN nanowires.

2. The photoluminescence (PL) and field emission properties of the prepared GaN nanowires were systematically investigated. The research progresses are as follows: