Approaching the Intrinsic Threshold Breakdown Voltage and Ultrahigh Gain in a Graphite/InSe Schottky Photodetector

Abstract

In conventional APDs, the charge amplification mechanism is based on a one-carrier cascade impact ionization process involving only one type of carriers. [9] To achieve pronounced charge amplification, that is, high avalanche gain, a large breakdown voltage is required to provide enough energy for each injected carrier to produce multiple cascade ionizations in an avalanche region defined by a length of multiple mean-free paths. This leads to a grand challenge that the ultrahigh avalanche gain and the low breakdown voltage cannot be realized simultaneously in the conventional APD materials. Moreover, the breakdown voltages reported to date in the experimental works have never approached the theoretical limit of breakdown voltage of 1.5 E g /e with high gain, [10] hindering the development of APDs with both low energy consumption and high sensitivity. Searching for novel APD materials with alternative mechanisms to realize charge amplification represents a highly promising solution for addressing such challenges.Recently, the emerging family of 2D materials and van der Waals (vdW) heterostructures has prompted a revolution in developing high-performance avalanche photodetectors due to their unique properties. [3,[11][12][13] In particular, the enhanced Coulomb interaction resulting from the quantum confinement in vdW layered materials could boost the ionization rate [12,14] during the process of impact ionization. Here, we propose a new type of APDs based on the vdW Schottky junction, and realize both intrinsic threshold breakdown voltage of 1.5 E g /e and ultrahigh avalanche gain up to ≈3 × 10 5 . Such an excellent performance of the vdW Schottky APD can be well explained by a 2D avalanche model. In addition, we find the temperature dependence of the breakdown voltage and the gain relies not only on the ionization process but also on the thermally assisted carrier collection process. Our work highlights the potential of the vdW Schottky junction for developing next-generation high-performance APDs. Results and DiscussionAs schematically shown in Figure 1a, vdW Schottky APD was fabricated based on graphite/InSe vdW heterostructures, Realizing both ultralow breakdown voltage and ultrahigh gain is one of the major challenges in the development of high-performance avalanche photodetector. Here, it is reported that an ultrahigh avalanche gain of 3 × 10 5 can be realized in the graphite/InSe Schottky photodetector at a breakdown voltage down to 5.5 V. Remarkably, the threshold breakdown voltage can be further reduced down to 1.8 V by raising the operating temperature, approaching the theoretical limit of 1.5 E g g /e, with E g g the bandgap of semiconductor. A 2D impact ionization model is developed and it is uncovered that observation of high gain at low breakdown voltage arises from reduced dimensionality of electron-phonon scattering in the layered InSe flake. These findings open up a promising avenue for developing novel weak-light detectors with low energy consumption and high sensitivity.

Drain-Induced Multifunctional Ambipolar Electronics Based on Junctionless MoS2

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Broadband and Ultra-High-Sensitivity Separate Absorption–Multiplication Avalanche Phototransistor Based on a Au–WSe2–Ge Heterostructure

“…Hence, at high temperatures, a larger bias voltage is required for carriers to attain sufficient energy for collision ionization. 43 To reveal the carrier transport type and the formation of the WSe 2 /Ge heterojunction in the device, the transfer characteristics of the WSe 2 FET (shown in the inset) and the I−V characteristics of the WSe 2 /Ge structure are measured, respectively. Figure 3a shows the I ds −V gs curves of the WSe 2 FET device measured at a drain-source voltage (V ds ) of −8 V. It should be noted that the WSe 2 sample without gate modulation (V g = 0 V) is n-type, which is transferred to a ptype material when V g increased in the negative direction.…”

“…The positive temperature coefficient of avalanche breakdown voltage can be ascribed to the greater energy loss of carriers due to lattice scattering at a higher temperature than that at a lower temperature. Hence, at high temperatures, a larger bias voltage is required for carriers to attain sufficient energy for collision ionization …”

Lanthanum Oxyhalide Monolayers: An Exceptional Dielectric Companion to 2-D Semiconductors

“…The everexpanding 2-D family, with over 4000 species predicted to date [4], [5], covers almost the entire spectrum of technologically important solid-states phases, including dielectric, semiconductor, semimetal, metal, and superconductors, as well as exotic condensed matter phases, such as topological insulator (TI), Dirac semimetal [6], Mott insulator [7], hourglass semimetal [8], and so on. Myriads of novel functional devices, such as computing electronics [9], [10], neuromorphic devices [11], energy-efficient electronics [12], reversible logical cells [13], terahertz devices [14], [15], renewable energy converters [16], and photodetectors [17], have been concretely demonstrated in the past decade.…”