Ⅲ-Ⅴ族氮化物发光二极管因具有寿命长、 尺寸小、 高效、 节能等优点, 得到广泛的研究与应用。 随着光通信、 万物互联等领域的进一步发展, 需要开发高质量的微纳光源和微纳光波导。 纳米柱氮化镓发光二级管(GaN-LED)是一种重要的微纳光源, 具有广阔的应用前景。 另一方面, 作为应用最广的硅半导体材料本身并不是直接半导体, 发光效率低下而不能作为光源使用。 因此, 研究基于硅基板的纳米柱GaN-LED微纳光源具有非常重要的意义。 采用射频分子束外延技术(MBE)在Si基板上沉积并生长具有GaN缓冲层、 Si掺杂的n-GaN层、 4个周期的InGaN/GaN量子阱层和Mg掺杂的p-GaN层的GaN基PN结构。 利用扫描电子显微镜(SEM)观察其表面和侧面形貌, 可观察到以一定的倾斜角度生长于衬底表面、 排列紧密且整齐的纳米柱。 利用微纳加工技术制备纳米柱GaN-LED, 对已获得的纳米柱外延片进行SOG填充、 FAB刻蚀, 在p-GaN层和Si衬底侧蒸镀电极, 并对LED两电极施加直流电压, 进行I/V曲线和电致发光(EL)特性的测试。 纳米柱GaN-LED的阈值电压为1.5 V, 在室温下的峰值波长为433 nm。 纳米柱结构可有效减小LED的阈值, 在相同电压情况下, 纳米柱LED的亮度更高, 展现了良好的发光特性。 GaN纳米材料与体材料相比, 纳米结构中存在应力弛豫可以有效地降低位错密度, 尺寸小于光生载流子或激子的扩散长度, 因而能够减小光电子器件激活层中的局域化效应。 通过TCAD仿真, 对与实验结构相同的纳米柱GaN-LED两电极分别施加5, 6和7 V的电压, 可得到纳米柱LED的发光光谱。 仿真结果显示纳米柱GaN-LED的发光波长在414~478 nm之间, 发光颜色为天青蓝到蓝紫色之间, 峰值波长为442 nm, 发出鲜亮蓝色的光, 与实验获得的EL光谱结果相近。 随电压增大, 发光光谱峰值波长减小, 出现轻微的峰值波长蓝移。 在纳米柱结构中InGaN/GaN区域产生强烈的极化效应, 纳米柱结构在量子阱区域的载流子浓度增加, 削弱了量子限制斯塔克效应, 从而使LED波长峰值向高频率移动即蓝移。 其次, 纳米柱结构能够引起应力释放, 也会引起峰值波长蓝移。

Ⅲ-Ⅴ nitride GaN light emitting diodes (LEDs) have been widely studied and applied due to their long lifetime, small size, high efficiency and energy saving. With the further development in the fields of optical communication and interconnection, it is necessary to develop high quality micro-nano photonic sources and waveguides. Nano-column GaN-LED is an important micro-nano light source which has a broad application prospect. On the other hand, the silicon semiconductor material which is the most widely used is not a direct semiconductor itself, and its luminous efficiency is low and cannot be used as a light source. Therefore, it is very important to study nano-column GaN-LED micro/nano light sources based on silicon substrates. In this paper, a GaN buffer layer, a Si-doped n-GaN layer, a 4-period InGaN/GaN quantum wells layer and a Mg-doped p-GaN layer were deposited and grown on Si substrate by radio frequency molecular beam epitaxy technology(rf-MBE). The surface and side morphology of the nanostructures were observed by scanning electron microscope (SEM). Nano-columns which were grown on the surface of the substrate at a certain oblique angle and arranged closely and neatly can be observed. Nano-column GaN-LED was prepared by micro-nano processing technology. SOG filling and FAB etching were performed on the obtained nano-pillar epitaxial wafer, and electrodes were vapor-deposited on the p-GaN layer and S substrate side. DC voltage was applied to both electrodes of the LED. Photoelectric properties such as I-V curves and electroluminescence (EL) spectra were tested. The results show that the threshold voltage of nano-column GaN-LED is 1.5 V and the peak wavelength of nano-column GaN-LED is 433 nm at 290 K. The nano-column structure effectively reduces the LED threshold with smaller voltage. At the same voltage, the nano-column LED has a higher brightness and exhibits better light emission characteristics. Compared with bulk materials, the existence of stress relaxation in the nanostructures can effectively reduce the dislocation density. The size of the nanostructure is smaller than the diffusion length of photo-generated carriers or excitons, reducing the localization in the active layer of the optoelectronic device. By the TCAD simulation, the luminescence spectra of the nano-column LED can be obtained by applying voltages of 5, 6 and 7 V to the two electrodes of the nano-column GaN-LED respectively. The wavelength of nano-column GaN-LED is 414~478 nm. The luminous color covers from sky blue to blue-purple and the peak wavelength is 442 nm, which is close to the 433 nm of the EL. As voltage increases, the peak wavelength of the emission spectrum decreases, with a slight blue shift of the peak wavelength. In the nano-pillar structure, the InGaN/GaN region produces a strong polarization effect, and the nano-column structure increases the carrier concentration in the quantum wells region, which weakens the quantum-confined Stark effect, thereby shifting the peak wavelength of the LED to a high frequency which is called blue shift. Moreover, the nanopillar structure can cause stress release and also cause a blue shift in peak wavelength.