The LWIR and longer wavelength regions are of particular interest for new developments and new approaches to realizing long-wavelength infrared (LWIR) photodetectors with high detectivity and high responsivity. These photodetectors are highly desirable for applications such as infrared earth science and astronomy, remote sensing, optical communication, and thermal and medical imaging. Here, we report the design, growth, and characterization of a high-gain band-structure-engineered LWIR heterojunction phototransistor based on type-II superlattices. The 1/e cut-off wavelength of the device is 8.0 µm. At 77 K, unity optical gain occurs at a 90 mV applied bias with a dark current density of 3.2 × 10⁻⁷ A/cm². The optical gain of the device at 77 K saturates at a value of 276 at an applied bias of 220 mV. This saturation corresponds to a responsivity of 1284 A/W and a specific detectivity of 2.34 × 10¹³ cm Hz^1/2/W at a peak detection wavelength of ~6.8 µm. The type-II superlattice-based high-gain LWIR device shows the possibility of designing the high-performance gain-based LWIR photodetectors by implementing the band structure engineering approach.

LWIR和更长的波长区域对于实现具有高探测性和高响应度的长波长红外（LWIR）光电探测器的新开发和新方法尤为重要。这些光电探测器非常适合诸如红外地球科学和天文学，遥感，光学通信以及热成像和医学成像等应用。在这里，我们报告基于II型超晶格的高增益带结构设计的LWIR异质结光电晶体管的设计，生长和特性。器件的1 / e截止波长为8.0 µm。在77 K时，施加90 mV偏压时会产生单位光学增益，暗电流密度为3.2×10 ^-7  A / cm ²。在220 mV的施加偏压下，该器件在77 K时的光学增益达到276的饱和值。该饱和度对应于在约6.8 µm的峰值检测波长下的1284 A / W的响应度和2.34×10 ¹³  cm Hz ^1/2 / W的比检测度。基于超晶格的II型高增益LWIR器件显示了通过实施能带结构工程方法设计高性能的基于增益的LWIR光电探测器的可能性。