A New Approach to Designing High-Sensitivity Low-Dimensional Photodetectors

Abstract

Photodetectors fabricated from low-dimensional materials such as quantum dots, nanowires, and two-dimensional materials show tremendous promise based on reports of very high responsivities. However, it is not generally appreciated that maximizing the internal gain may compromise the detector performance at low light levels, reducing its sensitivity. Here, we show that for most low-dimensional photodetectors with internal gain the sensitivity is determined by the junction capacitance. Thanks to their extremely small junction capacitances and reduced charge screening, low-dimensional materials and devices provide clear advantages over bulk semiconductors in the pursuit of high-sensitivity photodetectors. This mini-review describes and validates a method to estimate the capacitance from external photoresponse measurements, providing a straightforward approach to extract the device sensitivity and benchmark against physical limits. This improved physical understanding can guide the design of low-dimensional photodetectors to effectively leverage their unique advantage and achieve sensitivities that can exceed that of the best existing photodetectors.

Mixed-Dimensional Anti-ambipolar Phototransistors Based on 1D GaAsSb/2D MoS2 Heterojunctions

“…On one hand, scaling down the device dimensions and applying local gating are expected to enhance the anti-ambipolar frequency doubling performance and enable higher operating frequencies accordingly . On the other hand, the shrinkage of the active region leads to reduced capacitance, thereby rendering the photodetectors intrinsically faster, more sensitive, and energy-efficient. − Last but not least, a high-quality and strongly coupled heterointerface is also crucial to produce an efficient charge transfer. In this regard, mixed-dimensional heterostructures consisting of 1D nanowires (NWs) and layered 2D materials offer an effective strategy for the design of multifunctional and high-performance anti-ambipolar optoelectronics.…”

All‐Printed Ultrahigh‐Responsivity MoS2 Nanosheet Photodetectors Enabled by Megasonic Exfoliation

“…NEP is obtained by explicit measurement of the noise spectral density ( S I ) in dark conditions (Figure S12, Supporting Information) since the shot‐noise limit of NEP is known to artificially inflate D *, particularly in nanoscale photodetectors that have large extrinsic gain. [ 20,21 ] The highest detectivity was 1.8 × 10 7 Jones at an intensity of 7 × 10 −5 W cm −2 . The sublinear power dependence, which is attributed to bimolecular recombination, agrees with previously reported CVD‐grown and mechanically exfoliated monolayer MoS 2 photodetectors (γ < 0), [ 22,23 ] but contrasts the superlinear power dependence (γ > 0) in previously reported solution‐processed MoS 2 and GaTe photodetectors that are explained by a two‐center Shockley–Read–Hall (SRH) model.…”

Ultrasensitive Ferroelectric Semiconductor Phototransistors for Photon‐Level Detection

“…[38][39][40][41] The response time of a photodetector is dependent on the RC time, which may be further optimized by optimizing the contact resistance and capacitance. [42] Note that an ultra-fast reset voltage pulse is acceptable for low-light-level detection just as a quench or reset circuit in a SPAD. [43] It is acceptable to add an ultra-fast reset voltage pulse in our work because in a traditional Single Photon Avalanche Diode (SPAD), a quench or reset circuit to restore the SPAD to its original state is also necessary.…”