GaN基MSM结构紫外探测器研究

【作者】 周飞跃；

【导师】 杨谟华；

【作者基本信息】 电子科技大学 ， 微电子学与固体电子学， 2006， 硕士

【摘要】 GaN基金属-半导体-金属(MSM)结构紫外探测器因其具有平面型、工艺简单、便于集成等优点而成为研究热门课题之一。当前,GaN基MSM结构紫外探测器在稳态光照下的电流和响应度随偏压变化的关系、实验中观测到的光增益现象以及持续光电导效应(PPC),都没有明确的理论解释,因此器件设计中难以保证GaN基MSM结构紫外探测器的性能。在现有理论基础上,利用MATLAB和MEDICI软件,对GaN基MSM紫外探测器进行了仿真,获得了该器件的暗电流与稳态光照下电流的I-V关系曲线。在使用现有理论的仿真结果中,获得的暗电流的I-V曲线与文献中实验数据一致,而稳态光照下I-V关系曲线与文献报道的实测结果在非饱和段不吻合。并且现有理论无法解释光增益现象,因此稳态光照下电流随偏压变化的关系成为本文研究的重点之一。通过求解一维电流连续性方程和传输方程,同时考虑表面态陷阱的作用,建立了GaN基MSM结构紫外探测器在稳态光照下I-V关系的解析模型。所建立模型的理论计算结果与文献报道的实测结果一致,该模型成功解释在非饱和段稳态光照下电流与响应度随偏压快速变化的原因。利用该模型推导了稳态光照下响应度方程,该方程能解释在GaN基MSM结构紫外探测器中出现的光增益现象。因为PPC效应对紫外探测器的灵敏度、噪声特性以及响应速度都有负面影响,且其缺少确定的理论解释,所以是论文研究的又一重点。利用MEDICI仿真软件和Shockley-Read-Hall模型研究了体内陷阱对PPC效应的影响,结果表明体内陷阱与PPC效应无关系。利用势垒复合模型和本文提出的稳态光照下I-V关系的解析模型对PPC效应进行研究,建立了光照停止后电流随时间衰减的解析模型,即PPC效应模型,该模型的计算结果与文献报道的实测结果基本吻合,证明了表面态陷阱是导致PPC效应的根本原因。结合本文建立的稳态光照下I-V关系的理论模型、光照停止后电流随时间衰减的解析模型以及当前国内外的研究成果,设计了一种无非线性、无PPC效应的低暗电流GaN基MSM结构紫外探测器,并使用MEDICI仿真软件进行了验证。更多还原

【Abstract】 GaN-based meta1-semiconductor-metal (MSM) structure ultraviolet photodetector has been one of the focuses of interest in recent years for its plane structure, fabrication simplicity, and easy integration. However, the mechanisms of the I-V characteristics under illumination, the photocurrent gain and the strong persistent photoconductivity (PPC) are still unexplained to this day. That’s why the quality of the photodetector can’t be insured.According to the existing theory, the dark I-V characteristics and the I-V characteristics under illumination are simulated using MATLAB software and MEDICI simulator. According the simulated results, the dark I-V curve is in agreement with the experimental date from literature, but the I-V curve under illumination doesn’t fit the experimental date from literature in the insaturation region. Furthermore, the existing theory can’t explain the photocurrent gain, so the I-V characteristics under illumination are the keystone of the research work.A model of I-V characteristics under illumination in GaN-based metal- semiconductor -metal photodetectors has been built, using steady-state continuity equations and including the effect of surface states. The predicted result by the model agrees with the experimental date from literature. The current under illumination and the responsivity change sharply with the biased voltage in the insaturation region can be explained by our model. The responsivity equation can be proposed from our model and be used to explain the photocurrent gain.The research of the PPC is another highlight. The effect of the traps in the epitaxial layer is analyzed using the MEDICI simulator and Shockley-Read–Hall model, which indicates the PPC is independent of the traps in the epitaxial layer. On the basis of the recombination model with traps located at a potential barrier and the model of the I-V characteristics under illumination that we have built, the model of the attenuation of the current after illumination is proposed. The model can explain the PPC soundly and indicate that the surface states are the cause of the PPC.According to the model of the I-V characteristics under illumination, the model of更多还原