"Fundamental Research on Amorphous Silicon Photosensor with Internal Multiplication Function"

在反向偏置条件下，在氢化非晶硅基p-i/a- SiN/i-n多层异质结中观察到光电流倍增。系统地研究了该结系统的光电流特性，包括光电流-电压特性、光强和工作温度依赖性、光谱依赖性和瞬态响应特性。从结果分析中发现，倍增是由价带“电子”穿过a-SiN势垒层的带间隧穿注入引起的。光电流倍增过程由三个关键的基本过程组成：(a) a- sin /a- si异质结界面上空穴的积累，(b)异质结上的场重分布，以及(c)载流子通过a- sin层能隙中的局域态的带间隧穿。基于实验数据的器件建模使我们能够设计器件结构以获得更好的器件性能。通过对器件结构的优化，在p - a- sic /i - a- si接口处具有a- sin（厚度为40nm，光能隙为2.1 eV）的异质结光电二极管在30V工作电压下获得了超过70的外量子效率，响应时间快至500 μ s。所提出的高灵敏度光电倍增管器件将具有广泛的应用领域，如用于高清电视的固态成像仪等。

Photocurrent multiplication has been observed in a hydrogenated amorphous silicon-based p-i/a- SiN/i-n multi ayered heterojunction under a reverse biased condition. A systematic investigation on the photocurrent characteristics in this junction system has been carried out, including photocurrent-voltage characteristics, light intensity and operation temperature dependences, spectral dependence and transient response characteristics. It has been found from the analysis of the results that multiplication arises from the interband tunneling injection of valence band "electron" through the a-SiN barrier layer. The photocurrent multiplication process is modeled to be comprised of three key elemental processes occurring sequentially in time: (a) accumulation of holes at the a-SiN/a-Si heterojunction interface, (b) field redistribution over the heterojunction, and (c) interband tunneling of carriers via the localized states in the a-SiN layer's energy gap. The device modeling on the basis of the experimental data permits us to design the device structure for achieving better device performances. By an optimization of device structure, an external quantum efficiency exceeding 70 with a response time as fast as 500 mus has been obtained under the operation voltage of 30V in the heterojunction photodiode provided with a-SiN (thickness of 40nm with optical energy gap 2.1 eV) at the p a-SiC/i a-Si interface. The proposed highly sensitive photomultiplier device would have a wide variety of application fields such as a solid-state imager for high-definitive television, and so on.