Photoelectric detection device based on germanium-barium titanate heterogeneous integration

Abstract

A photoelectric detector based on Ge-BTO heterogeneous integration comprises a silicon dioxide substrate layer which is a basic structure of the whole device and provides stable support for other layers. And the BTO passive device layer is positioned on the silicon dioxide substrate and comprises three main parts: an input waveguide, a transition conical waveguide and a flat plate structure waveguide. Wherein the input waveguide is responsible for receiving and transmitting an optical signal to a device; and the transition conical waveguide is connected with the input waveguide and the slab structure waveguide. The shape design is to reduce the transmission loss of an optical signal, so that the optical signal can be more efficiently transited from a narrower input waveguide to a wider flat plate structure waveguide. And the slab structure waveguide is used for transmitting optical signals in the device. The structure of the slab waveguide can accommodate and transmit optical signals in a larger range, and is suitable for subsequent photoelectric conversion or detection. And the germanium absorption layer is responsible for photoelectric signal conversion and forms a source electrode and a drain electrode of the transistor through partial doping. And the oxide layer forms an insulating layer in the transistor. And the polycrystalline germanium layer forms a grid electrode of the transistor so as to regulate and control the light current.

Description

Technical Field

[0001] The invention relates to the technical field of photoelectric detection, in particular to a photoelectric detection device based on heterogeneous integration of germanium-barium titanate (Ge-BTO). Background Art

[0002] Barium titanate (BaTiO3, BTO) material has been widely used in integrated optical modulation devices and passive devices due to its ultra-high first-order optical nonlinearity. A fully functional integrated optical chip for optical communication needs to have the ability to transmit, receive and process optical signals. Receiving optical signals usually requires the use of the photoelectric effect of the material, that is, when the photon energy is greater than the bandgap width of the material, the electrons in the valence band absorb the photon energy and transition to the conduction band, and are eventually collected by the metal electrode into a photocurrent to complete light detection. However, BTO's bandgap width of up to 3.4eV makes it impossible to use it directly for light detection in the optical communication band, and related research on BTO started relatively late, and there are no reports of BTO photodetectors yet. Existing composite semiconductor material platforms for this type of large bandgap width are mostly based on lithium niobate platforms. There are currently several methods to solve the problem of difficulty in manufacturing photodetectors on wide bandgap semiconductor material platforms:

[0003] (1) Amorphous silicon (a-Si) and metal electrodes are deposited on lithium niobate film in sequence, and a metal-semiconductor-metal (MSM) structure is constructed to form a Schottky junction to generate a photothermal electron effect and realize photoelectric conversion. However, the inherent barrier height between semiconductors and metals makes this type of photodetector have a low responsivity; the large dark current of the MSM structure itself significantly increases the noise level of the channel. These two shortcomings seriously damage the signal-to-noise ratio of the communication system. Therefore, this method is difficult to use for optical communication.

[0004] (2) Heterogeneous integration of III-V photodetectors on a lithium niobate platform by wafer bonding. This method can maintain the responsiveness and response time of III-V detectors to a high degree. However, the on-chip integration of III-V materials is currently still limited to the single integration of devices onto wafer bare die, making it difficult to achieve mass production. In addition, due to the energy band differences between III-V materials, numerous conduction band smoothing layers and depletion absorption layers are required to help electrons pass through the material interface. The complex and cumbersome process increases production costs.

[0005] (3) Integrate two-dimensional materials such as graphene and molybdenum disulfide on lithium niobate thin films, and use the broadband response and large gain of two-dimensional materials to obtain high photoelectric response. However, since two-dimensional materials are only atomic layer thick, their integration with wafer bare chips is still limited to manual transfer and patching, and the stability is poor, which is still a long way from mass production.

[0006] In general, the above solutions cannot take into account both process complexity and device performance when constructing photodetectors on a wide bandgap semiconductor material platform. The complex additional process flow undoubtedly increases the production cost of high-performance photodetectors. Therefore, a new solution is urgently needed to realize photodetectors on a wide bandgap semiconductor material platform, which has the advantages of low cost, easy implementation, and large-scale production while maintaining device performance. Summary of the invention

[0007] The present invention proposes a germanium-barium titanate (Ge-BTO) heterogeneously integrated high-responsivity photodetector that can be applied to real-time optical power detection in a barium titanate thin film on-chip optical path system. The sensitivity of the detection device is improved by utilizing the heterogeneous growth characteristics of germanium-barium titanate lattice matching and combining the gain mechanism of a field effect transistor and a dark current compensation circuit. The detector has the advantages of high sensitivity, low cost, easy implementation, and large-scale production.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0009] A photoelectric detection device based on Ge-BTO heterogeneous integration, which is characterized by:

[0010] Silicon dioxide substrate layer: This is the basic structure of the entire device, providing a stable support for other layers.

[0011] BTO passive device layer: located on the silicon dioxide substrate, it includes three main parts: input waveguide, transition tapered waveguide and slab structure waveguide. Among them, input waveguide: responsible for receiving and transmitting optical signals into the device. Transition tapered waveguide: connects the input waveguide and the slab structure waveguide. Its shape is designed to reduce the transmission loss of the optical signal, so that the optical signal can more efficiently transition from the narrower input waveguide to the wider slab structure waveguide. Slab structure waveguide: used to transmit optical signals inside the device. The structure of the slab waveguide enables it to accommodate and transmit a wider range of optical signals, which is suitable for subsequent photoelectric conversion or detection.

[0012] Ge phototransistor component layer: horizontally grown on the upper surface of the BTO passive device layer, it is the core part of the photodetector device, including:

[0013] Heterogeneous growth of germanium layer: as a medium for conversion of optical signals and electronic signals.

[0014] Oxide isolation layer: located on the upper surface of the heterogeneously grown germanium layer, used to isolate and protect the underlying germanium layer, while providing insulation between the gate and the germanium layer.

[0015] The first polycrystalline germanium gate layer and the second polycrystalline germanium gate layer: These two gate structures are respectively located on the upper surface of the oxide isolation layer and are used to control the current in the heterogeneous growth germanium layer. The polycrystalline germanium gate layer, the N heavily doped region and the oxide isolation layer together form a phototransistor structure.

[0016] Phototransistor structure: The photovoltaic effect is utilized. When light is irradiated to the germanium layer, electron-hole pairs are generated. These electron-hole pairs generate current under the action of the gate electric field, thereby realizing the conversion of optical signals into electrical signals.

[0017] Upper cladding layer: covers the upper surface of the BTO passive device layer and the Ge phototransistor component, plays a role in protecting the device and isolating it from the external environment.

[0018] Furthermore, the heterogeneously grown Ge layer includes a first N heavily doped region, a first intrinsic region, a second N heavily doped region, a second intrinsic region, and a third heavily doped region. The right side of the first N heavily doped region is connected to the left side of the first intrinsic region, the right side of the first intrinsic region is connected to the left side of the second N heavily doped region, the right side of the second N heavily doped region is connected to the left side of the second intrinsic region, and the right side of the second intrinsic region is connected to the left side of the third N heavily doped region. The first polycrystalline germanium gate is located directly above the first intrinsic region, and forms a first phototransistor structure with the first N heavily doped region, the second N heavily doped region, and the oxide isolation layer. The second polycrystalline germanium gate is located directly above the second intrinsic region, and forms a second phototransistor structure with the second N heavily doped region, the third N heavily doped region, and the oxide isolation layer.

[0019] The BTO device layer includes an input waveguide, a transition tapered waveguide and a planar structure waveguide.

[0020] The top of the input waveguide is connected to the narrow end of the transition tapered waveguide, and the wide side of the transition tapered waveguide is connected to the bottom end of the planar structure waveguide. The input waveguide and the transition tapered waveguide are both located directly below the first intrinsic region.

[0021] A first source is prepared on the first N heavily doped region by depositing metal and etching metal, and a common drain is prepared on the second N heavily doped region by the same method, a second source is prepared on the third N heavily doped region, a first gate is prepared on the first polycrystalline germanium gate region, and a second gate is prepared on the second polycrystalline germanium gate region.

[0022] The first source, the second source and the common drain are located on the upper surface of the heterogeneous growth Ge layer, and the first gate and the second gate are located on the upper surface of the first and second polycrystalline germanium gates respectively. The oxide isolation layer material is thermally grown germanium oxide material with a thickness of several nm to more than ten nm; the upper cladding layer is made of silicon dioxide material.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] The present invention constructs a Ge differential phototransistor pair structure on a BTO material platform, which can not only achieve high detection sensitivity by relying on the internal photocurrent gain of the phototransistor, but also can reduce the dark current of the device by relying on the high-quality epitaxial growth of germanium on BTO, with fewer internal defects in the film. In the application scenario of BTO on-chip optical power meter, it replaces the traditional photodetector constructed by amorphous silicon materials, III-V materials, and two-dimensional materials, and solves some problems such as poor quality, difficulty, instability, and difficulty in mass production of heterogeneous integrated materials on BTO. The present invention realizes efficient reception, transmission, and detection of optical signals, and has broad application prospects in the fields of optical communication, optical sensing, and photoelectric detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the cross-sectional structure of the present invention;

[0026] Figure 2 It is a schematic diagram of the main functional structure of the present invention;

[0027] Figure 3 is a schematic diagram of average distribution of the 0th order transverse electric mode electric field on a cross section when the input working wavelength is 1.55 μm in an embodiment of the present invention;

[0028] Figure 4 is an electric field evolution diagram of the 0th order transverse electric mode electric field along the transmission direction of the device when the input working wavelength is 1.55 μm in an embodiment of the present invention;

[0029] Figure 5 The relationship curve between the source-drain current of the germanium phototransistor on a single BTO and the polycrystalline germanium gate voltage is shown in FIG.

[0030] Explanation of the marks in the figure: 1. Silicon dioxide substrate layer; 2. BTO device layer; 3. Heterogeneous growth germanium layer; 4. Oxide isolation layer; 5. Upper cladding layer; 6. First N-heavy doped region; 7. First intrinsic region; 8. Second N-heavy doped region; 9. Second intrinsic region; 10. Third N-heavy doped region; 11. First source; 12. First gate; 13. Common drain; 14. Second gate; 15. Second source; 16. First polycrystalline germanium gate; 17. Second polycrystalline germanium gate; 18. Input waveguide; 19. Transition tapered waveguide; 20. First phototransistor structure; 21. Second phototransistor structure; 22. Planar waveguide structure. DETAILED DESCRIPTION

[0031] In order to better understand the structure and function of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings. The following examples are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0032] Embodiment: The present invention provides a BTO material platform germanium photodetector structure for constructing a Ge differential phototransistor pair on a BTO film, including two germanium phototransistor structures and a BTO passive device structure therebelow, such as Figure 1 and Figure 2 As shown. After forming a heterogeneous growth Ge layer 3 on BTO by thin film deposition, the present invention forms N-heavy doped regions 6, 8, 10 in Ge by N-type ion implantation to ensure good electrode contact, and retains intrinsic regions 7, 9 of equal width between adjacent N-heavy doping. After forming a germanium oxide isolation layer 4 by thin film deposition, polycrystalline germanium gate structures 16, 17 and metal electrodes 11, 12, 13, 14, 15 are formed by processes such as ion beam etching and magnetron sputtering.

[0033] like Figure 4 As shown, when the input mode is the 0th order transverse electric mode (TE0) and the wavelength is 1.55 μm, the light enters the slab structure waveguide 22 via the input waveguide structure 18 and the transition tapered waveguide 19, and because the refractive index of BTO is much smaller than that of the upper layer of germanium and polycrystalline germanium, most of the input light is confined in the first polycrystalline germanium gate 16 and the germanium layer structure directly below it.

[0034] like Figure 3 , which shows a schematic diagram of the distribution of the average light absorption along the propagation direction in the cross section of the first phototransistor structure 20 when the input light mode is the 0th order transverse electric mode (TE0) and the operating wavelength is 1.55μm. Since there are many defects inside the polycrystalline germanium, the absorption coefficient is much larger than the heterogeneous growth Ge layer 3, so the light absorption mainly occurs in the first polycrystalline germanium gate region, and the photogenerated carriers are mainly concentrated in the first polycrystalline germanium gate region, and a small amount is distributed in the first intrinsic region.

[0035] like Figure 5As shown, when a 1V forward DC voltage bias is applied between the source and the drain, the relationship curve of the current between the first source and the common drain changes with the forward DC voltage applied to the gate 12. A 1.5V forward DC bias voltage is applied to the source 11, and the common drain 13 is grounded. On the one hand, in the case of light input, when the DC bias voltage applied by the gate 12 is less than 1.5V, a conductive N channel is not formed on the top of the intrinsic region 7. Since the intrinsic region is a Ge material with high resistivity, the current between the source 11 and the drain 13 is very small, and the transistor works in the cut-off state; when the DC bias voltage applied by the gate 12 is greater than or equal to 1.5V, a conductive N channel is formed on the top of the intrinsic region 7, the resistance between the source and the drain decreases rapidly, and the current increases rapidly. On the other hand, when there is light input, due to the gate threshold effect, a large number of unbalanced photogenerated carriers distributed on the gate can form a conductive N channel at the top of the first intrinsic region in advance, so when the input light power is 0.1mW, the current between the source and drain has a photocurrent change of about 0.32mA, and the corresponding light responsivity is 3.1A / W. Furthermore, when the input light power drops to a weak light input of 0.01mW, the photocurrent under 2V gate bias remains at the 0.1mA level, and the responsivity is increased to 10A / W.

Claims

1. A photoelectric detection device based on heterogeneous integration of germanium-barium titanate (Ge-BTO), characterized in that: include: Silicon dioxide substrate layer; A BTO passive device layer is disposed on the upper surface of the silicon dioxide substrate layer, and includes an input waveguide, a transition tapered waveguide and a slab structure waveguide, wherein the input waveguide is connected to the narrow end of the transition tapered waveguide, and the wide end of the transition tapered waveguide is connected to the slab structure waveguide; A Ge phototransistor component layer is horizontally grown on the upper surface of the BTO passive device layer, and includes a heterogeneous growth germanium layer, an oxidation isolation layer, a first polycrystalline germanium gate layer, and a second polycrystalline germanium gate layer, wherein the oxidation isolation layer is located on the upper surface of the heterogeneous growth germanium layer, and the first polycrystalline germanium gate layer and the second polycrystalline germanium gate layer are both located on the upper surface of the oxidation isolation layer; the heterogeneous growth germanium layer is composed of a first N-heavy doped region, a first intrinsic region, a second N-heavy doped region, a second intrinsic region, and a third heavily doped region connected in sequence; the first polycrystalline germanium gate is located directly above the first intrinsic region, and forms a first phototransistor structure with the first N-heavy doped region, the second N-heavy doped region, and the oxidation isolation layer; the second polycrystalline germanium gate is located directly above the second intrinsic region, and forms a second phototransistor structure with the second N-heavy doped region, the third N-heavy doped region, and the oxidation isolation layer; The upper cladding layer covers the upper surfaces of the BTO passive device layer and the Ge phototransistor component layer.

2. The Ge-BTO heterogeneous integrated photodetector device according to claim 1, characterized in that: The input waveguide and the transition tapered waveguide are both located directly below the first intrinsic region.

3. The Ge-BTO heterogeneous integrated photodetector device according to claim 1 or 2, characterized in that: Also includes: A first source electrode is formed on the upper surface of the first N heavily doped region; A drain electrode is formed on the upper surface of the second N heavily doped region; A second source electrode is formed on the upper surface of the third N heavily doped region; A first gate is formed on the upper surface of the first polycrystalline germanium gate layer; The second gate is prepared on the upper surface of the second polycrystalline germanium gate layer.

4. The Ge-BTO heterogeneous integrated photodetector device according to claim 1 or 2, characterized in that: The oxide isolation layer is a thermally grown germanium oxide material with a thickness of several nanometers to more than ten nanometers; the upper cladding layer is a silicon dioxide material.

5. The Ge-BTO heterogeneous integrated photodetector device according to claim 1 or 2, characterized in that: The Ge optical transistor component is grown on the upper surface of the BTO passive device layer by using a heteroepitaxial growth technique.

6. The Ge-BTO heterogeneous integrated photodetector device according to claim 1 or 2, characterized in that: The heterogeneously grown germanium layer is replaced by a bonding Ge layer.

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