A black phosphorus thin film lithium niobate detector

Abstract

The invention discloses a black phosphorus thin film lithium niobate detector, the detector structure is sequentially as follows from bottom to top: the first layer is an intrinsic silicon substrate (1), the second layer is a buried oxide layer (2), the third layer is a thin film lithium niobate waveguide (3), the fourth layer is black phosphorus (4), and the fifth layer is a metal electrode; wherein the buried oxide layer is directly oxidized on the intrinsic silicon substrate; the thin film lithium niobate is bonded to the buried oxide layer to define a thin film lithium niobate waveguide with a longitudinal ridge by etching; the black phosphorus is laterally covered on the middle section of the ridge of the thin film lithium niobate waveguide, and is closely connected to the thin film lithium niobate waveguide through van der Waals force; the first metal electrode (5‑1) and the second metal electrode (5‑2) are respectively covered on both sides of the black phosphorus and the thin film lithium niobate waveguide ridge. The detector of the invention has the characteristics of high speed, broadband, high response, high integration, etc., and provides a solution for the development of on-chip photonic integrated circuits.

Description

Technical Field

[0001] The invention belongs to the field of waveguide integrated two-dimensional material photoelectric detection, and in particular relates to a black phosphorus thin film lithium niobate detector. Background Art

[0002] On-chip photonic integrated circuits can provide a universal platform for revolutionary development in photonic computing, fiber-optic communications, biosensing, lidar and other fields. A key technology for the application and breakthrough of photonic integrated circuits is to realize high-speed and low-power transceiver modules, which requires the development of high-speed, low dark current and high-response waveguide integrated photodetectors.

[0003] There are many materials for developing on-chip photonic integrated circuits. Among them, thin-film lithium niobate can support the transmission of visible light with shorter wavelengths, and theoretically has a higher carrier bandwidth than silicon optoelectronic devices. Current research results have shown that thin-film lithium niobate waveguides can achieve low power consumption, high linearity, and ultra-high-speed electro-optical modulation. However, this material cannot absorb light signals and has difficulties in photoelectric detection. To solve this problem, two-dimensional materials and thin-film lithium niobate waveguides can be heterogeneously integrated to realize waveguide-integrated photodetectors.

[0004] Two-dimensional materials refer to single-layer or few-layer layered materials in which the atoms in the layers are tightly bound by covalent bonds. In addition, the chemical covalent bonds of each layer of the two-dimensional material are fully saturated, there are no dangling bonds on the surface of the material, and adjacent layers are connected by van der Waals forces. Therefore, two-dimensional materials can be directly integrated heterogeneously on the substrate. Among them, black phosphorus, as an in-plane anisotropic two-dimensional material, has high carrier mobility and narrow direct band gap. Its excellent performance in broadband detection, integration capability and polarization sensitivity makes it stand out from other candidates and become an attractive photon absorption material for realizing waveguide integrated photodetectors. Summary of the invention

[0005] Technical problem: In view of this, an embodiment of the present invention proposes a black phosphorus thin film lithium niobate detector, which combines the advantages of two-dimensional materials and a new waveguide structure to achieve a high-performance waveguide integrated two-dimensional material photoelectric detector.

[0006] Technical solution: The present invention provides a black phosphorus thin film lithium niobate detector, the detector structure from bottom to top is: the first layer is an intrinsic silicon substrate, the second layer is a buried oxide layer, the third layer is a thin film lithium niobate waveguide, the fourth layer is black phosphorus, and the fifth layer is a metal electrode; wherein the buried oxide layer is directly oxidized on the intrinsic silicon substrate; the thin film lithium niobate is bonded to the buried oxide layer and a longitudinal ridge-shaped thin film lithium niobate waveguide is defined by etching; the black phosphorus laterally covers the middle section of the ridge of the thin film lithium niobate waveguide and is tightly connected to the thin film lithium niobate waveguide through van der Waals force; the first metal electrode and the second metal electrode respectively cover the two sides of the black phosphorus and the thin film lithium niobate waveguide ridge.

[0007] The intrinsic silicon substrate has a thickness of 0.4-0.7 mm.

[0008] The buried oxide layer is made of silicon dioxide and has a thickness of 1-3 microns.

[0009] The thin film lithium niobate waveguide is a ridge waveguide, including a ridge in the upper part and a plate in the lower part. The ridge width is 0.5-12 microns, the ridge thickness is 0.15-0.45 microns, the plate thickness is 0.15-0.45 microns, the angle between the ridge side wall and the horizontal plane is 50-90 degrees, and it can support single-mode or multi-mode light fields.

[0010] The black phosphorus-covered thin-film lithium niobate waveguide has a thickness of 1-200 nanometers.

[0011] The first metal electrode covers black phosphorus and thin-film lithium niobate waveguide and has a thickness of 50-100 nanometers.

[0012] The second metal electrode covers black phosphorus and thin-film lithium niobate waveguide and has a thickness of 50-100 nanometers.

[0013] The working principle is as follows: the black phosphorus thin-film lithium niobate detector heterogeneously integrates black phosphorus with a thin-film lithium niobate waveguide. A buried oxide layer is provided above the intrinsic silicon substrate, and the mode is limited by the thin-film lithium niobate waveguide located above the buried oxide layer, which can achieve better device isolation. Black phosphorus is used as the photon absorption material. Under the condition of no light coupling, only a small channel current passes through the device; when light is coupled to the waveguide, black phosphorus absorbs photons to generate photocurrent, completing the conversion of optical signals to electrical signals.

[0014] Beneficial effects: Compared with the prior art, the present invention heterogeneously integrates black phosphorus with thin-film lithium niobate waveguide. Signal light is limitedly transmitted in the thin-film lithium niobate waveguide, and is absorbed by black phosphorus in the active area and converted into a current signal.

[0015] The advantages of the embodiments of the present invention are:

[0016] 1) Using thin-film lithium niobate as the waveguide material can provide high-speed electro-optic modulation.

[0017] 2) Black phosphorus is used as the conductive channel material. Black phosphorus has the advantages of high carrier mobility, in-plane anisotropy and adjustable band gap, which can realize broadband (ultraviolet-mid-infrared) and high-speed photoelectric detection.

[0018] 3) The detector has the characteristics of high speed, broadband, high response and high integration, providing a solution for the development of on-chip photonic integrated circuits. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 A schematic diagram of the cross-sectional structure of a black phosphorus thin film lithium niobate detector provided in an embodiment of the present invention.

[0021] Figure 2 A top view of a black phosphorus thin film lithium niobate detector provided in an embodiment of the present invention.

[0022] Figure 3 Mode field distribution diagram of a black phosphorus thin film lithium niobate detector provided in an embodiment of the present invention.

[0023] The figure includes: an intrinsic silicon substrate 1, a buried oxide layer 2, a thin film lithium niobate waveguide 3, black phosphorus 4, a first metal electrode 5-1, and a second metal electrode 5-2. DETAILED DESCRIPTION

[0024] See also Figure 1 The embodiment of the present invention provides a black phosphorus thin film lithium niobate detector, the detector structure from bottom to top is: the first layer is an intrinsic silicon substrate 1, the second layer is a buried oxide layer 2, the third layer is a thin film lithium niobate waveguide 3, the fourth layer is black phosphorus 4, and the fifth layer is a metal electrode; wherein the buried oxide layer 2 is directly oxidized on the intrinsic silicon substrate 1; the thin film lithium niobate is bonded to the buried oxide layer 2 and a longitudinal ridge-shaped thin film lithium niobate waveguide 3 is defined by etching; the black phosphorus 4 is laterally covered on the middle section of the ridge of the thin film lithium niobate waveguide 3, and is tightly connected to the thin film lithium niobate waveguide 3 through van der Waals force; the first metal electrode 5-1 and the second metal electrode 5-2 are respectively covered on both sides of the ridge of the black phosphorus 4 and the thin film lithium niobate waveguide 3.

[0025] The intrinsic silicon substrate 1 has a thickness of 0.4-0.7 mm and mainly supports the entire photodetector.

[0026] The buried oxide layer 2, in this embodiment, the buried oxide substrate layer can be silicon dioxide with a thickness of 1-3 microns, which mainly plays the role of supporting the entire photodetector.

[0027] The thin film lithium niobate waveguide 3 is arranged on the buried oxide layer 2. The waveguide type is ridge-shaped, including a ridge in the upper part and a plate in the lower part. The ridge width is 0.5-12 microns, the ridge thickness is 0.15-0.45 microns, the plate thickness is 0.15-0.45 microns, and the angle between the ridge sidewall and the horizontal plane is 50-90 degrees. The light incident through the grating coupler is limited to be transmitted in the thin film lithium niobate waveguide 3.

[0028] Black phosphorus 4 is disposed on the thin-film lithium niobate waveguide 3 and has a thickness of 1-200 nanometers. It absorbs the signal light guided in the thin-film lithium niobate waveguide 3 and converts it into a current signal.

[0029] The first metal electrode 5 - 1 is disposed on one side of the black phosphorus 4 and the thin-film lithium niobate waveguide 3 , covering the black phosphorus layer and the thin-film lithium niobate waveguide.

[0030] The second metal electrode 5 - 2 is disposed on the other side of the black phosphorus layer 4 and the thin-film lithium niobate waveguide layer 3 , covering the black phosphorus layer and the thin-film lithium niobate waveguide.

[0031] Among them, the first metal electrode 5-1 and the second metal electrode 5-2 can be made of titanium, chromium, gold or other conductive metals. The first metal electrode 5-1 and the second metal electrode 5-2 can be made of the same metal material or different metal materials. For example, the first metal electrode 5-1 can be a titanium or titanium-plated electrode, and the second metal electrode 5-2 can be a gold or gold-plated electrode, which is not specifically limited in the present invention. The first metal electrode 5-1 and the second metal electrode 5-2 can be a single metal electrode or a composite metal electrode. For example, the first metal electrode 5-1 and the second metal electrode 5-2 can be a gold electrode, or a composite metal electrode with a lower metal of titanium and an upper metal of gold, which is not specifically limited in the present invention. The lateral distances between the first metal electrode 5-1 and the second metal electrode 5-2 and the ridge sidewall of the thin film lithium niobate waveguide layer 3 can be the same or different, which is not specifically limited in the present invention.

[0032] In this embodiment, when the signal light is transmitted in the thin-film lithium niobate waveguide 3, it is absorbed by the black phosphorus 4 covering the thin-film lithium niobate waveguide 3 to generate photocarriers. With the action of the external electric field applied with a bias voltage, the photocarriers will be rapidly separated in the black phosphorus 4 and drift toward the first metal electrode 5-1 and the second metal electrode 5-2, respectively, to form a photocurrent signal passing through the black phosphorus 4. These photocurrent signals pass through the first metal electrode 5-1 and the second metal electrode 5-2 and are received by the corresponding device.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A black phosphorus thin film lithium niobate detector, characterized in that: The detector structure is as follows from bottom to top: the first layer is an intrinsic silicon substrate (1), the second layer is a buried oxide layer (2), the third layer is a thin film lithium niobate waveguide (3), the fourth layer is black phosphorus (4), and the fifth layer is a metal electrode; wherein the buried oxide layer (2) is directly oxidized on the intrinsic silicon substrate (1); the thin film lithium niobate is bonded to the buried oxide layer (2) and a thin film lithium niobate waveguide (3) with a longitudinal ridge is defined by etching; the black phosphorus (4) covers the middle section of the ridge of the thin film lithium niobate waveguide (3) laterally and is tightly connected to the thin film lithium niobate waveguide (3) through van der Waals force; the first metal electrode (5-1) and the second metal electrode (5-2) cover the two sides of the ridge of the black phosphorus (4) and the thin film lithium niobate waveguide (3) respectively; The buried oxide layer (2) is made of silicon dioxide and has a thickness of 1-3 micrometers; The thin-film lithium niobate waveguide (3) is a ridge waveguide, comprising a ridge in the upper part and a plate in the lower part, the ridge width is 0.5-12 microns, the ridge thickness is 0.15-0.45 microns, the plate thickness is 0.15-0.45 microns, the angle between the ridge sidewall and the horizontal plane is 50-90 degrees, and it can support single-mode or multi-mode light fields; The black phosphorus (4) covers the thin film lithium niobate waveguide, with a thickness of 1-200 nanometers; The first metal electrode (5-1) covers black phosphorus and thin-film lithium niobate waveguide and has a thickness of 50-100 nanometers; The second metal electrode (5-2) covers black phosphorus and thin-film lithium niobate waveguide and has a thickness of 50-100 nanometers.

2. The black phosphorus thin film lithium niobate detector according to claim 1, characterized in that: The intrinsic silicon substrate (1) has a thickness of 0.4-0.7 mm.

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