Unipolar barrier structures are used to suppress dark current in photodetectors by blocking majority carriers. Designing unipolar barriers with conventional materials is challenging due to the strict requirements of lattice and band matching. Two-dimensional materials have self-passivated surfaces and tunable band structures, and can thus be used to design unipolar barriers in which lattice mismatch and interface defects are avoided. Here, we show that band-engineered van der Waals heterostructures can be used to build visible and mid-wavelength infrared unipolar barrier photodetectors. Our nBn unipolar barrier photodetectors, which are based on a tungsten disulfide/hexagonal boron nitride/palladium diselenide heterostructure, exhibit a low dark current of 15 pA, a photocurrent of 20 μA and a detectivity of 2.7 × 10¹² cm Hz^1/2 W⁻¹. Our pBp unipolar barrier photodetectors, which are based on a black phosphorus/molybdenum disulfide/graphene heterostructure, exhibit a room-temperature detectivity of 2.3 × 10¹⁰ cm Hz^1/2 W⁻¹ in the mid-wavelength infrared region under blackbody radiation. The pBp devices also show a dichroic ratio of 4.9 under blackbody radiation, and a response time of 23 μs under 2 μm laser illumination.

单极势垒结构用于通过阻挡多数载流子来抑制光电探测器中的暗电流。由于晶格和能带匹配的严格要求，使用传统材料设计单极势垒具有挑战性。二维材料具有自钝化表面和可调能带结构，因此可用于设计避免晶格失配和界面缺陷的单极势垒。在这里，我们展示了带工程范德华异质结构可用于构建可见光和中波长红外单极势垒光电探测器。我们的 nBn 单极势垒光电探测器基于二硫化钨/六方氮化硼/二硒化钯异质结构，具有 15 pA 的低暗电流、20 μA 的光电流和 2.7 × 10 ^{12的检测率} 厘米赫兹^1/2  W ^-1。我们的 pBp 单极势垒光电探测器基于黑磷/二硫化钼/石墨烯异质结构，在黑体辐射下的中波长红外区域表现出 2.3 × 10 ¹⁰  cm Hz ^1/2  W ^{-1的室温探测率。}pBp 器件在黑体辐射下的二向色比为 4.9，在 2 μm 激光照射下的响应时间为 23 μs。