吸收层特性和异质结界面电荷对12.5 μm长波HgCdTe光伏探测器响应率的影响研究

研究了12.5 μm长波HgCdTe探测器的吸收层厚度和异质结界面电荷对器件光响应率的影响.分析了吸收层厚度与吸收长度、扩散长度之间的联系，获得了设计最佳吸收层厚度的经验公式.研究结果显示入射光波长超过截止波长时，响应率随吸收层厚度增加单调增加，并逐渐饱和.响应率峰值对应的波长随吸收层厚度增加，有向长波偏移的趋势.最佳吸收层厚度值随少子寿命或入射光波长的增大而增大.同时，研究了衬底、钝化层与HgCdTe材料之间异质界面电荷对光响应率的影响，发现正的界面电荷在衬底异质结界面处形成诱导pn结，对响应率影响显著 关键词： 长波HgCdTe器件 光伏型红外探测器 光响应率 少子寿命

Effects of absorption layer parameters and hetero-interface charge on photoresponse of 12.5 long-wavelength HgCdTe photodiode

The effects of absorption layer parameters and hetero-interface charge on photoresponse of long-wavelength HgCdTe photodiode have been studied. The correlations between thickness of absorption layer and absorption length and diffusion length are investigated. An empirical formula is proposed to estimate the optimal thickness of absorption layer. Our theoretical investigations indicate that, when the wavelength of incident light is longer than the cut-off wavelength, the photoresponse monotonically increases with the increase of absorption layer thickness, and saturates subsequently. The wavelength of the maximal photoresponse increases with the increase of absorption layer thickness, and tends to shift toward long wavelength region. The optimal absorption layer thickness increases with increasing minority carrier life time and wavelength of incident light. It is found that the positive interface charge can induce a p-n junction at the substrate interface and significantly reduce the photoresponse. By using the metal-oxide-semiconductor diode model, possible physics mechanisms are investigated, and an approach is proposed to reduce the effects of hetero-interface charge on the photoresponse.