Abstract：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.
张雨茜，陆志成，张 伟，郭俊宏，张雪花，胡芳仁. 硅基纳米柱GaN-LED的制备与光谱特性分析[J]. 光谱学与光谱分析, 2019, 39(08): 2450-2453.
ZHANG Yu-xi, LU Zhi-cheng, ZHANG Wei, GUO Jun-hong, ZHANG Xue-hua, HU Fang-ren. Study of the Fabrication and Spectral Analysis of Silicon-Based Nanocolumn GaN-LED. SPECTROSCOPY AND SPECTRAL ANALYSIS, 2019, 39(08): 2450-2453.
