表面等离激元增强的背照式氮化物堆栈结构APD机理研究

The UV detection of weak light even “single-photon” level signal with ultra-high sensitive and low noise has significant application value in many fields, such as secure communications, missile warning and guidance, deep space exploration. The existing nitride APD shows small electrons and holes ionization coefficient ratio, which can only work in Geiger mode when detect the single photon. It cannot distinguish the number of photons and need long dead time and quenching circuit. The nitride APD with stacked structure can achieve high gain from electrons unipolar ionization by increasing the electrons and holes ionization coefficient ratio. Here the stacked structure was proposed to be the multiplication region of integratable back-illuminated nitride APD. Plasmonic structure was employed to collect and couple the back-illuminated light into absorbing region, which can solve the problem of poor effective absorption. Both the effective absorption and electrons unipolar ionization can be increased dramatically by our method. Based on the previous researches about the theory of unipolar ionization multiplication in stacked structure and front-illuminated nitride APD, we will study the design and fabrication of surface-plasmon-enhanced back-illuminated unipolar ionization ultraviolet APD. The mechanism of absorption and multiplication in the new APD structure will be also revealed. The back-illuminated ultraviolet APD with linear-mode gain more than 10000 and responsivity more than 1000 A/W at constant high reverse bias will be realized. The research will provide a novel idea for the significant demand of integratable “single-photon” level signal detection without the need of quenching circuit.

高灵敏度、低噪声的“单光子”级别微弱紫外光探测在保密通信、预警与制导、火灾预警等众多领域具有重大应用价值。现有氮化物APD的电子和空穴离化系数接近，只能在盖革模式下探测极弱光，无法区分光子数、死时间较长且需要淬灭电路。堆栈结构氮化物APD可增大电子-空穴离化系数比，实现高增益电子单极离化。本项目提出将堆栈结构倍增区引入易集成的背照式APD中，采用表面等离激元结构解决背照式下有效光吸收低的问题。从而使其对光子的吸收和电子的单极倍增能力都得到大幅提升。拟在前期堆栈倍增区的理论研究及正入射APD制备基础上，设计并制备光耦合增强的背照式堆栈结构APD，揭示新结构器件中的吸收及倍增机理。最终实现背照式线性工作模式的紫外APD探测器，线性增益>10000，恒定高反偏压下响应率>1000 A/W。为高响应率“单光子级”极微弱紫外光探测的重大需求提供一条无需周期性淬火电路且适于集成的新思路。

高灵敏度、低噪声的“单光子”级别微弱紫外光探测在保密通信、预警与制导、火灾预警等众多领域具有重大应用价值。现有氮化物APD的电子和空穴离化系数接近，只能在盖革模式下探测极弱光，无法区分光子数、死时间较长且需要淬灭电路。堆栈结构氮化物APD可增大电子-空穴离化系数比，实现高增益电子单极离化。本项目将堆栈结构倍增区引入易集成的背照式APD探测器件中，采用表面等离激元结构解决背照式下有效光吸收低的问题。研究了堆栈倍增区的理论研究，获得正照式周期性堆栈结构探测器件，其线性增益60000，在此外延和工艺基础上制备出背照式线性工作模式的紫外探测器件，由于背照式外延质量低于正照式器件，增益有所降低，经过多轮优化，背照式堆栈型器件线性增益1.2E4，在-70V高反偏压下响应率1070A/W。完成了背照式氮化物堆栈型探测器件与等离激元耦合结构的集成，为高响应率“单光子级”极微弱紫外光探测的重大需求提供一条无需周期性淬火电路且适于集成的新思路。