面向红外探测应用的硅基飞秒激光超饱和掺杂和表面微纳结构形成机理研究及可控加工

The infrared absorption can be greatly enhanced by femtosecond laser hyper doping. It draws people’s interesting because its potential to fabricate silicon based photodetector with increased infrared response. The key to extend the infrared response of silicon based photodetector is the balance of the efficiency of absorption and carrier extraction, which require the control of the dopant density, distribution, thickness of the doped layer and the light trapping surface structures. To achieve a better infrared performance, this project focuses on the fundamental questions of the optimization and control of the properties of hyper doped silicon. .An in-situ pump-probe system, which has a working time range at 100fs-1μs, will be setup with the double-side reflection strategy to increase the detection capability. The interface response function in the process of femtosecond laser hyper doping and nanosecond laser annealing will be investigated. A dynamic model, based on the combination of the two temperature model, thermal expansion and nonlinear continuous growth model will be established to study the mechanism to tailor the density, distribution and thickness of the dopant. Based on the dielectric function measured by an in-situ dual-angle pump-probe system upon the irradiation of a femtosecond laser, a multi physics model contains Sipe-Drude model, hydro dynamics, FDTD method and holographic ablation model to investigate the gas assisted nonlinear etch and surface structures formation. The black silicon with optimized properties can be obtained based on the research. The silicon based photodetector, which has better infrared responsivity, will be fabricated.

飞秒激光超饱和掺杂能大幅提高硅的红外吸收，是加工高响应硅基红外探测器的希望。硅基红外探测器响应范围拓展的关键是精确控制杂质浓度、分布及掺杂层厚度和可控加工具有光俘获特性的表面微纳结构。本项目面向红外探测，围绕黑硅性能优化和可控加工的关键科学问题，搭建大时间范围原位泵浦-探测系统，通过双面反射法提高可测液体硅厚度范围，原位测量飞秒激光超饱和掺杂、纳秒激光退火过程中的固-液界面响应函数；结合双温模型、热扩散理论和非线性连续生长理论，建立超饱和掺杂动力学模型，研究杂质浓度、分布及掺杂层厚度的调控原理和方法，实现精确控制；基于双角度泵浦-探测，原位测量飞秒激发下的介电函数，结合Sipe-Drude模型、流体力学、热弹性力学、FDTD和全息消融法建立多物理场混合模型，研究气体辅助飞秒激光非线性刻蚀、表面微纳结构产生及演化机理，实现微纳结构主动控制；优化黑硅性能，加工硅基红外探测器，实现增强红外探测。

红外探测在安防、医学、通信、国防、工业等国民生产、生活的关键领域都有至关重要的作用。受限于带隙宽度，硅基探测器对于波长长于1.1 μm的光几乎不响应。超饱和掺杂的黑硅具有几乎平坦的红外吸收，易于与现有半导体工艺集成，是理想的宽谱红外探测器材料。然而，黑硅探测器的红外工作范围依旧有限，限制了其广泛应用。要拓宽黑硅红外探测器的工作波段范围，其关键是对掺杂的材料特性及表面自组织生长的微纳结构进行精确调控，这需要对飞秒激光超饱和掺杂动力学、表面微纳结构产生机理等展开深入研究。.本项目面向飞秒激光超饱和掺杂黑硅制备、性能改善中涉及到的关键科学问题，搭建了具有亚皮秒时间分辨、纳秒时间尺度的原位泵浦探测系统，研究了飞秒激光超饱和掺杂中的融化、再凝固过程，探究了通过能流密度进行结晶度调控的物理机理，获得了具有高结晶度和高红外吸收的黑硅；原位研究了掺杂对黑硅中载流子动力学的影响。建立了多物理场耦合模型，研究了飞秒诱导产生表面微纳结构的产生、演化的过程及机理；探究了通过基底温度调控表面微纳结构的物理机制，揭示了影响微纳结构结晶度的关键因素，实现了高结晶度微纳结构制备。研究了薄膜辅助飞秒激光刻蚀，获得了远超衍射极限的极小周期表面微纳结构，研究了这类表面微纳结构的产生机理和调控方法，实现了大面积极小周期表面微纳结构制备。项目达到了预期的研究目标，圆满完成了预定的研究任务。