阻挡杂质带红外探测器中的界面势垒效应

通过变温暗电流和变偏压光电流谱实验对阻挡杂质带红外探测器的跃迁机理和输运特性进行了研究. 结合器件能带结构计算的结果, 证明了在阻挡杂质带红外探测器中主要由导带底下移效应引起的界面势垒的存在. 提出了阻挡杂质带红外探测器的双激发工作模型, 并从变偏压光电流谱中成功地分离出了与这两种物理过程所对应的光谱峰, 进一步证实了器件的能带结构. 研究了界面势垒效应对阻挡杂质带红外探测器的光电流谱、响应率和内量子效率的影响. 研究表明, 考虑进界面势垒效应, 计算得到的器件响应率与实验值符合得很好. 同时发现阻挡杂质带红外探测器中内建电场的存在等效降低了发生碰撞电离增益所需的临界电场强度.

Interfacial barrier effects in blocked impurity band infrared detectors

Blocked impurity band (BIB) detectors, developed from extrinsic detectors, have long been employed for ground-based and airborne astronomical imaging and photon detections. They are the state-of-the-art choice for highly sensitive detection from mid-infrared to far-infrared radiation. In this work, we demonstrate the existence of an interfacial barrier in blocked impurity band structures by evidence of temperature-dependent dark currents, bias-dependent photocurrent spectra and corresponding theoretical calculations. The origin of the build-in field is studied. The temperature-dependent characteristics of space charge effects are also investigated in detail. It is found that at higher temperature (T >14 K), the space charge influence is negligible, and the interfacial barrier is mainly caused by bandgap narrowing effects. Based on interfacial barrier effects, a dual-excitation model is proposed to clarify the band structure of BIB detectors. The photocurrent spectra related to the two excitation processes, i.e., the direct excitation over the interfacial barrier and excitation to the band edge with subquent tunneling into blocking layer, are successfully extracted and agree reasonably well with the calculated band structure results. The effects of interfacial barrier on the photocurrent spectrum, peak responsivity and internal quantum efficiency of the devices are investigated. With the consideration of interfacial barrier effects, the calculated peak responsivity shows good agreement with the experimental result. It is suggested that interfacial barrier effects should be considered for successfully designing the BIB detectors. Additionally, the build-in field is found to equivalently lower the critical field for impact ionization. This study provides a better understanding of the working mechanism in BIB detectors and also a better device optimization.