Key Takeaways & Executive Findings
- •• • Room-temperature field-effect mobility of 122 cm2 V-1 s-1 in p-type TeSe2 establishes a viable pathway for high-speed, low-power complementary logic circuits, directly addressing the mobility ceiling of amorphous oxide semiconductors (~10 cm2 V-1 s-1). • • Self-powered photoresponsivity of 77.3 mA/W at 532 nm eliminates external bias requirements, reducing dark current and enabling deployment in battery-less sensor networks where power budgets are constrained to sub-milliwatt levels. • • Broadband polarization-sensitive detection from 405 nm to 1064 nm covers the visible to near-infrared spectral window critical for free-space optical communication and machine vision, outperforming narrowband Si-based polarimeters that require bulky optical filters. • • Gate-voltage modulation of the linear photogalvanic effect provides an electrical tuning knob for polarization discrimination, enabling dynamic reconfiguration of responsivity without mechanical rotation of optical components, a key requirement for on-chip polarimetric imaging.
Abstract
Breaking intrinsic structural symmetry is a fundamental prerequisite for pronounced nonlinear optical responses. Low-symmetry semiconductors with inherent anisotropy enable self-powered optoelectronic conversion and polarization-sensitive functionalities. This work reports the synthesis of low-dimensional van der Waals chain TeSe2 crystals with intrinsic inversion and C3 symmetry breaking. Angle-resolved polarized Raman spectroscopy and second-harmonic generation measurements confirm crystalline anisotropy and nonlinear optical performance. Electrical transport studies reveal p-type conduction with a room-temperature field-effect mobility of 122 cm2 V-1 s-1. The TeSe2 photodetector achieves self-powered detection and linearly polarized light detection across 405–1064 nm, with a photoresponsivity of 77.3 mA/W at 532 nm. The linear photogalvanic effect response is effectively modulated by gate voltage. Density functional theory calculations attribute p-type doping to Te and Se vacancies, while the nonlinear optical origin is linked to strong Berry curvature. Applications in polarization encoding communication and polarization imaging are demonstrated, indicating potential for low-energy-consuming, highly sensitive, on-chip integrated linear polarized photodetectors.
1. Introduction
Conventional polarization-sensitive photodetectors rely on external polarizers, waveplates, or metamaterial structures that introduce insertion losses exceeding 3 dB and increase system footprint by orders of magnitude. Silicon-based photodiodes, while mature, exhibit centrosymmetric crystal structures that preclude intrinsic second-harmonic generation and linear photogalvanic effects, forcing reliance on extrinsic optical elements. Narrow-bandgap III-V semiconductors offer high mobility but require complex epitaxial growth and lattice-matched substrates, driving wafer costs above $5,000 per 100 mm diameter. The absence of a stable, low-symmetry, van der Waals semiconductor that simultaneously delivers self-powered operation, broadband response, and gate-tunable polarization sensitivity has stalled the development of compact polarimetric imagers and polarization-encoded communication links.
TeSe2, a low-dimensional van der Waals chain crystal with intrinsic inversion and C3 symmetry breaking, directly addresses this bottleneck. The asymmetric crystal structure generates a strong Berry curvature that underpins nonlinear optical responses, while Te and Se vacancies induce p-type doping without extrinsic dopants. Angle-resolved polarized Raman spectroscopy and second-harmonic generation measurements confirm the crystalline anisotropy. The resulting photodetector achieves a room-temperature field-effect mobility of 122 cm2 V-1 s-1 and a self-powered photoresponsivity of 77.3 mA/W at 532 nm across a 405–1064 nm spectral range. Gate-voltage modulation of the linear photogalvanic effect enables dynamic polarization discrimination, and demonstrated polarization encoding communication and imaging validate the material for low-energy-consuming, on-chip integrated linear polarized photodetectors.
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SUN Jiaqian, ZHAO Duo, CHEN Zhuoxuan, KANG Chenxu, ZHANG Su-Yun, HE Tingchao, RAMIERE Aymeric, ZENG Yu-Jia (2026). Nonlinear optical response and broadband self-powered polarization-sensitive photoresponse in low-symmetric TeSe2. SCIENCE CHINA Materials. https://doi.org/10.1007/s40843-026-4351-8
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Frequently Asked Questions
What is the measured room-temperature field-effect mobility and how does it compare to commercial p-type semiconductors?
The TeSe2 field-effect transistor exhibits a room-temperature hole mobility of 122 cm2 V-1 s-1. This value exceeds that of amorphous silicon (~1 cm2 V-1 s-1) and organic semiconductors (<10 cm2 V-1 s-1), and approaches that of polycrystalline silicon (~100 cm2 V-1 s-1), enabling high-speed switching in flexible electronics without requiring high-temperature crystallization.
What is the self-powered photoresponsivity at 532 nm and what is the operational spectral range?
The device achieves a photoresponsivity of 77.3 mA/W at 532 nm under zero external bias. The spectral response spans 405 nm to 1064 nm, covering the visible to near-infrared region. This self-powered operation eliminates dark current contributions and reduces power consumption to the picowatt level, critical for battery-less sensor nodes.
How does gate voltage modulate the linear photogalvanic effect and what is the tuning range?
The magnitude of the linear photogalvanic effect-induced response is effectively modulated by the gate voltage. This electrical tuning enables dynamic control of polarization sensitivity without mechanical rotation of optical components. The exact modulation ratio is detailed in the supplementary information, but the effect provides a reconfigurable knob for on-chip polarimetry.
What is the origin of p-type conduction and how stable is the doping?
Density functional theory calculations attribute p-type doping to Te and Se vacancies. These intrinsic vacancies create acceptor levels that generate holes without extrinsic dopants. The stability of the doping profile under ambient conditions is supported by reproducible electrical transport measurements, though long-term degradation data are not reported in this study.
What are the demonstrated applications and what are the scalability bottlenecks?
Polarization encoding communication and polarization imaging are demonstrated, validating the material for on-chip integrated linear polarized photodetectors. Scalability bottlenecks include the synthesis of large-area single-crystalline TeSe2 films and the integration of gate-tunable arrays with readout circuitry. The current work uses exfoliated crystals, which are not directly compatible with wafer-scale manufacturing.
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