Carrier confinement in type-I 2D van der Waals heterostructures: Band-alignment engineering and emerging photodetection applications

Abstract

Type-I band alignment in two-dimensional (2D) van der Waals (vdW) heterostructures offers a compelling platform for carrier confinement, enabling optoelectronic functionalities distinct from widely studied type-II systems. Unlike charge-separating architectures, type-I configurations localize both electrons and holes within the same material. This carrier confinement promotes enhanced radiative recombination and can suppress dark current, which is advantageous for photodetection. In this focused review, we examine the fundamental mechanisms governing carrier confinement in type-I 2D vdW heterostructures, including band-offset engineering, interfacial coupling, and quantum confinement effects. Theoretical frameworks, such as Anderson's rule and density functional theory, are discussed to clarify band alignment formation and tunability. We further summarize recent advances in the design of lateral and vertical vdW heterostructures, emphasizing interface engineering strategies for precise control of electronic properties. Key experimental and computational techniques, including Kelvin probe force microscopy and first-principles simulations, are highlighted for probing interfacial energetics and validating band alignment. Finally, we critically evaluate recent progress in photodetectors based on type-I vdW heterostructures, demonstrating their potential for broadband operation, high responsivity, and fast response. Emerging opportunities and remaining challenges are outlined to guide future development of confined-carrier optoelectronic systems.