Cai Qing, You Haifan, Hou Qianyu, Tao Tao, Xie Zili, Cao Xun, Liu Bin, Chen Dunjun, Lu Hai, Zhang Rong, Zheng Youdou
Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China.
Collaborative Innovation Center for Optoelectronic Semiconductors and Efficient Devices, Department of Physics, Xiamen University, Xiamen 361005, China.
ACS Appl Mater Interfaces. 2022 Jul 27;14(29):33525-33537. doi: 10.1021/acsami.2c06417. Epub 2022 Jul 13.
As a burgeoning wide-band gap semiconductor material, AlGaN alloy has attracted great attention for versatile applications due to its superior properties. However, its poor crystalline quality has restricted the employment of AlGaN on electronic devices for a long time. Herein, we proposed a nanopillar/superlattice hierarchical structure for AlGaN epitaxy to boost the crystalline quality. The scale-controllable AlN nanopillar template is fabricated from a nickel self-assembly process. AlGaN initiates the epitaxial laterally overgrowth mode based on the nanopatterned template. In addition, the AlGaN/AlGaN superlattice structure could effectively block the propagation of threading dislocation segments. The kinetics of the dislocation and epitaxy process in the hierarchical structure is intuitively demonstrated and analyzed. Consequently, the dislocation density of AlGaN grown by this method is significantly reduced by more than 30 times compared to the AlN template. No threading dislocation segments were observed in the 4 μm TEM field of view. Moreover, based on the hierarchical structure, we also fabricated an AlGaN ultraviolet avalanche photodiode (APD). The APD exhibits superior performance, achieving a maximum gain of 1.3 × 10 and high responsivity of 1.46 A/W at 324 nm. The reliability of the nanopillar/superlattice AlGaN epitaxial procedure is anticipated to shed new light on the nitride semiconductor material, further bringing a breakthrough to wide-band gap electronic devices.
作为一种新兴的宽带隙半导体材料，AlGaN合金因其优异的性能在多种应用中备受关注。然而，其较差的晶体质量长期以来限制了AlGaN在电子器件中的应用。在此，我们提出了一种用于AlGaN外延的纳米柱/超晶格分级结构，以提高晶体质量。可控制尺度的AlN纳米柱模板通过镍自组装工艺制备。AlGaN基于纳米图案化模板启动外延横向过生长模式。此外，AlGaN/AlGaN超晶格结构可有效阻挡位错段的传播。直观地展示并分析了分级结构中位错和外延过程的动力学。因此，与AlN模板相比，用这种方法生长的AlGaN的位错密度显著降低了30倍以上。在4μm的透射电镜视野中未观察到位错段。此外，基于这种分级结构，我们还制备了一个AlGaN紫外雪崩光电二极管（APD）。该APD表现出优异的性能，在324nm处实现了1.3×10的最大增益和1.46A/W的高响应度。纳米柱/超晶格AlGaN外延工艺的可靠性有望为氮化物半导体材料带来新的启示，进一步为宽带隙电子器件带来突破。
