Xu Xuejun, Hashimoto Hideaki, Sawano Kentarou, Maruizumi Takuya
Opt Express. 2017 Mar 20;25(6):6550-6560. doi: 10.1364/OE.25.006550.
We demonstrate germanium (Ge) microdisks surrounded by highly reflective circular Bragg gratings on highly n-doped germanium-on-insulator (GOI) substrate. The GOI substrate is fabricated by wafer bonding from Ge grown on Si substrate, and n-type doping concentration of 2.1×10 cm is achieved by phosphorus diffusion from a spin-on-dopant source. Very sharp Fabry-Perot resonant peaks with high contrast fringes and Q-factors up to 400 are observed near the direct band gap of Ge in photoluminescence spectra. The reflectivity of gratings are enhanced by a factor larger than 3 in a wide wavelength range from 1.57 to 1.82 µm, compared with that of Ge/SiO interfaces in normal microdisks without circular Bragg gratings. The surface emission intensity of the devices is found to be increased by the grating period. Our results indicate that GOI microdisk with circular Bragg grating is a promising optical resonator structure suitable for realizing low threshold, compact Ge lasers integrated on Si substrate.
我们展示了在高度n型掺杂的绝缘体上锗（GOI）衬底上，被高反射率圆形布拉格光栅包围的锗（Ge）微盘。该GOI衬底通过将生长在硅衬底上的锗进行晶圆键合制成，通过从旋涂掺杂源进行磷扩散实现了2.1×10¹⁹ cm⁻³的n型掺杂浓度。在光致发光光谱中，在锗的直接带隙附近观察到了具有高对比度条纹和高达400的品质因数的非常尖锐的法布里 - 珀罗共振峰。与没有圆形布拉格光栅的普通微盘中的Ge/SiO界面相比，在1.57至1.82 µm的宽波长范围内，光栅的反射率提高了3倍以上。发现器件的表面发射强度随光栅周期增加。我们的结果表明，具有圆形布拉格光栅的GOI微盘是一种有前途的光学谐振器结构，适用于实现集成在硅衬底上的低阈值、紧凑型锗激光器。
