CN114400267B - Photoelectric detector integrated with double absorption areas and preparation method thereof - Google Patents

Abstract

The invention relates to the field of integrated chips and discloses a photodetector integrated with dual absorption areas and a preparation method thereof, which includes a base arranged from bottom to top, a second absorption active area, a light transmission waveguide area and a first absorption active area. Source region; a first P++ doped region, a first P+ doped region, a first intrinsic I region, a first N+ doped region and a first N++ doped region are arranged laterally in the first absorption active region, and the first The P++ doped region is electrically connected to the first metal electrode; a second P++ doped region, a second P+ doped region, a second intrinsic I region, and a second N+ doped region are arranged laterally in the second absorption active region. and a second N++ doped region, the second P++ doped region is electrically connected to the second metal electrode; the first and second N++ doped regions are electrically connected through a metal through hole. This photodetector has two different light absorption areas, can detect high-power and multi-band optical signals, has a high responsivity and a large photo-electric response bandwidth.

Description

Photodetector integrated with dual absorption areas and preparation method thereof

Technical field

The invention relates to the field of integrated chips, and in particular to a photodetector integrated with dual absorption areas and a preparation method thereof.

Background technique

Photo-electric detectors are generally used to detect light or other electromagnetic energy. Currently, detectors have important practical applications in wired or wireless communications, sensing, monitoring, and national security fields. Specifically, in the photo-electronic integrated chip, the photo-electric detector is one of the core chips at the receiving end, which converts high-speed optical data into electrical signals. Generally speaking, photo-electric detectors use materials with thermoelectric effect, photoelectric effect, and electric absorption effect to detect the intensity of light. In the optical communication band, the main material systems currently based on are III-V materials, germanium (Ge), and silicon (Si). Although detectors based on these material systems have achieved good performance and have been commercialized, they still have many shortcomings, such as single optical response wavelength, large device size, complex preparation process, and high cost.

Contents of the invention

Purpose of the invention: In view of the problems existing in the prior art, the present invention provides a photodetector integrated with dual absorption areas and a preparation method thereof. The photodetector has two different light absorption areas and can detect high power and Multi-band optical signals have higher responsivity and larger optical-electrical response bandwidth.

Technical solution: The present invention provides a photodetector integrated with dual absorption areas, including a substrate, a second absorption active area, a light transmission waveguide area and a first absorption active area arranged sequentially from bottom to top; The first absorption active region includes a first P++ doped region, a first P+ doped region, an undoped first intrinsic I region, a first N+ doped region and a first N++ doped region arranged laterally in sequence, The first P++ doped region is electrically connected to the first metal electrode; the second absorption active region includes a second P++ doped region, a second P+ doped region, and an undoped second P++ doped region arranged laterally in sequence. The intrinsic I region, the second N+ doped region and the second N++ doped region, the second P++ doped region is electrically connected to the second metal electrode; the first N++ doped region and the second N++ doped region The doped regions are electrically connected through metal vias between them.

Further, a groove structure is provided in the middle of the light transmission waveguide area. The refractive index (mode effective refractive index) of an optical waveguide is generally determined by the intrinsic refractive index of the material and the structure of the waveguide; generally speaking, adjusting the waveguide structure is a common and effective method, which will help design the coupling between waveguides Efficiency; For the groove structure in this application, parameters such as the depth and width of the groove, as well as the width and thickness of the external optical waveguide section can be changed to achieve adjustment of the refractive index; the equivalent benefit of this groove structure is that it increases By adjusting the dimensions of the refractive index, more adjustment parameters are available to achieve efficient optical coupling of the light transmission waveguide area with the first light absorption area and the second light absorption area.

Preferably, the width w1 of the first intrinsic I region is 50~500 nm; and/or the width w2 of the second intrinsic I region is 50~500 nm. The width of the first intrinsic I region and the second intrinsic I region will affect the 3dB bandwidth and detection quantum efficiency of the detector. If the width is too wide, the 3dB bandwidth will decrease, and if the width is too narrow, the quantum efficiency of the detection will decrease. Controlling it within 50~500nm can obtain a suitable 3dB bandwidth and detection quantum efficiency. Preferred are 50nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, etc., but are not limited to the listed values, and other unlisted values within this range are also applicable.

Further, part of the first P+ doped region, the first intrinsic I region and part of the first N+ doped region form a first light absorption region; part of the second P+ doped region, the The second intrinsic I region and part of the second N+ doped region form a second light absorption region; the light transmission waveguide region is located between the first light absorption region and the second light absorption region.

Preferably, the distance h1 between the light transmission waveguide area and the first light absorption area is 50~400 nm; and/or the distance h2 between the light transmission waveguide area and the second light absorption area. is 50~400nm. The distance between the light transmission waveguide area, the first light absorption area and the second light absorption area will affect the detection efficiency and optical power detection range of the detector. If the distance is too large, the light coupled into the absorption area will have less energy, which will reduce the detection efficiency. Small will cause the light absorption area to easily saturate under high power incidence, resulting in a smaller detection light power range table. Controlling the distance between the two at 50~400nm will help achieve high efficiency and high optical power detection. 50nm and 100nm are preferred. , 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, etc., but are not limited to the listed values, and other unlisted values within this numerical range are also applicable.

Preferably, the doping concentrations of the first P++ doped region, the second P++ doped region, the first N++ doped region and the second N++ doped region are 1×10 ²⁰ /cm respectively. ³ ~ 8×10 ²⁰ /cm ³ ; and/or, the first P+ doped region, the second P+ doped region, the first N+ doped region and the second N+ doped region The doping concentrations are 1×10 ¹⁸ /cm ³ ~6×10 ¹⁸ /cm ³ respectively.

Preferably, the first intrinsic I region and the second intrinsic I region are light absorbing materials with different light absorption wavelength bands. Since different materials correspond to different light absorption ranges, this is determined by the energy band structure of the material; for example, the light absorption waveguide of general silicon can only reach 1.1um and below. Light greater than 1.1um is generally no longer absorbed or absorbed by silicon materials. The efficiency is very low; germanium material can absorb light with wavelengths of 1.6um and below; but germanium material has a lower absorption efficiency below 1um compared to silicon material, so light below 1um is preferentially detected and absorbed by silicon; light above 1um is prioritized Detection of absorption with germanium. The configuration of different absorption bands in the first and second light absorption areas in this application enables the detection of broad spectrum light signals.

Preferably, the first intrinsic I region is any one of the following light-absorbing materials: germanium, germanium-silicon alloy, Group III-V material or Group III-V material alloy; and/or the second intrinsic I region is Any of the following light-absorbing materials: silicon or perovskite.

Preferably, the substrate is silicon-on-insulator SOI, which is formed by depositing silicon dioxide on a silicon substrate; and/or the material of the light transmission waveguide region is silicon nitride, aluminum nitride or lithium niobate.

The invention also provides a method for preparing a photodetector integrated with a double absorption region. The preparation method is as follows: (1) Deposit an insulating layer on the substrate to form a base, and deposit a third insulating layer on the base. 2. Absorb the active area film and form a ridge germanium waveguide structure after photolithography and etching; (2) P++ doping, N++ doping, P+ doping, and N+ doping are performed on the ridge germanium waveguide structure in sequence to form the third Two P++ doped regions, a second N++ doped region, a second P+ doped region, a second N+ doped region, and an undoped second intrinsic I region remain to form a second absorption active region; ( 3) Deposit an insulating layer and planarize it. After opening the window by photolithography, deposit the light transmission waveguide area material at the appropriate position to form the light transmission waveguide area; (4) Deposit the insulating layer, and deposit the metal through-hole material after photolithography and etching. , to form metal through holes; (5) Deposit the first absorption active area material, and form a ridge silicon waveguide structure after photolithography and etching; (6) Perform P++ doping, N++ doping, and P+ doping and N+ doping respectively form the first P++ doping region, the first N++ doping region, the first P+ doping region and the first N+ doping region, and retain the undoped first intrinsic I area to form a first absorption active area; (7) photolithography opens a window, and deposits a first metal electrode and a second metal electrode on the first P++ doped area and the second P++ doped area respectively.

Beneficial effects: In the photodetector integrated with dual absorption areas in the present invention, light passes through the light transmission waveguide area and is coupled to the first light absorption area and the second light absorption area respectively, benefiting from the first and second light absorption areas. The configuration of different absorption bands in the area can detect broad-spectrum optical signals; since the active area structure of the first and second light absorption areas is PNNP, and is loaded between the two P by the first metal electrode and the second metal electrode The bias voltage realizes the extraction of photogenerated carriers and generates electrical signals.

This photodetector can make the first and second light absorption areas work independently by changing the positive and negative bias voltages (see the attached figure of the abstract for details on the working principle), thus achieving integration. Here’s how it works:

This photodetector is a structure in which two PINs and NIPs are connected in series through N connections; when a voltage is applied between the two Ps, one of the two PN junctions will definitely work in forward bias and the other in reverse bias ( The basic principle of PN junction); the detector must work in the reverse polarized state to extract photogenerated carriers for signal detection; for example, when the wavelength of the incident light is λ1, coupling to the first light absorption area requires the first PIN If the junction works in reverse bias, then the second PIN junction will work in forward bias (detection cannot be realized); when the incident light wavelength is λ2, it is coupled to the second light absorption area, and the second PIN junction needs to work in reverse bias ( It can be realized by adjusting the voltage V _B ), then the first PIN junction will work forward bias (detection cannot be realized); and to achieve the reverse bias operation of the first and second PIN junctions respectively, you only need to adjust the load on the two P-type The voltage difference between them is enough.

Description of the drawings

Figure 1 is a schematic structural diagram of a photodetector integrated with dual absorption regions in the present invention;

Figure 2 is a schematic diagram of the working principle of a photodetector integrated with dual absorption regions.

Detailed ways

The present invention will be introduced in detail below with reference to the accompanying drawings.

This embodiment provides a photodetector integrated with dual absorption regions, including a substrate 1, a second absorption active region, a light transmission waveguide region 2 and a first absorption active region arranged in sequence from bottom to top.

The above-mentioned substrate 1 is a silicon-on-insulator SOI formed by depositing silicon dioxide 102 on a silicon substrate 101;

The above-mentioned second absorption active region includes a second P++ doped region 9, a second P+ doped region 10, an undoped second intrinsic I region 11, a second N+ doped region 12, and a second P++ doped region 10 arranged laterally. The N++ doped region 13, the second P++ doped region 9 and the second metal electrode 14 are electrically connected; part of the second P+ doped region 10, the second intrinsic I region 11 and part of the second N+ doped region 12 form a second Two-light absorption zone.

Among them, the doping concentrations of the second P++ doped region 9 and the second N++ doped region 13 are both 1×10 ²⁰ /cm ³ ~8×10 ²⁰ /cm ³ ; the second P+ doped region 10 and the second N+ The doping concentration of the doping region 12 is 1×10 ¹⁸ /cm ³ ~6×10 ¹⁸ /cm ³ . The second intrinsic I region 11 is made of silicon material, and the width w2 is 50~500nm.

The material of the above-mentioned light transmission waveguide region 2 is silicon nitride. In order to achieve efficient optical coupling between the light transmission waveguide area 2 and the first light absorption area and the second light absorption area, the light transmission waveguide area 2 in this embodiment is also provided with a groove structure capable of adjusting the refractive index.

The above-mentioned first absorption active region includes a first P++ doped region 3, a first P+ doped region 4, an undoped first intrinsic I region 5, a first N+ doped region 6 and a first P++ doped region 6 arranged laterally. The N++ doped region 7, the first P++ doped region 3 and the first metal electrode 8 are electrically connected; part of the first P+ doped region 4, the first intrinsic I region 5 and part of the first N+ doped region 6 form a third A light absorption area.

Among them, the doping concentrations of the first P++ doped region 3 and the first N++ doped region 7 are both 1×10 ²⁰ /cm ³ ~8×10 ²⁰ /cm ³ ; the first P+ doped region 4 and the first N+ The doping concentration of the doping region 6 is 1×10 ¹⁸ /cm ³ ~6×10 ¹⁸ /cm ³ . The first intrinsic I region 5 is made of germanium material, and the width w2 is 50~500nm.

The first N++ doped region 7 and the second N++ doped region 13 are electrically connected through the metal through hole 15 between them.

The distance h1 between the above-mentioned light transmission waveguide area 2 and the first light absorption area is 50~400nm; the distance h2 between the above-mentioned light transmission waveguide area 2 and the second light absorption area is 50~400nm.

The working principle of the above-mentioned photodetector integrated with dual absorption areas is shown in Figure 2:

This photodetector is composed of two PINs and NIPs connected in series through N connections; when a voltage is applied between the two Ps, one of the two PN junctions will work in forward bias and the other in reverse bias (PN junction Basic principle); the detector must work in a reverse-biased state to extract photogenerated carriers for signal detection; for example, when the wavelength of the incident light is λ1, it is coupled to the first light absorption area and requires the first PIN junction to work In reverse bias, then the second PIN junction will work in forward bias (detection cannot be realized); when the incident light wavelength is λ2, it is coupled to the second light absorption area, and the second PIN junction needs to work in reverse bias, then the third One PIN junction will work forward-biased (detection cannot be realized); to realize the reverse-biased operation of the first and second PIN junctions respectively, you only need to adjust the voltage difference loaded between the two P-types.

The preparation method of the above-mentioned photodetector integrated with dual absorption regions is as follows:

(1) On the silicon-on-insulator (SOI) substrate 1, use the plasma enhanced chemical vapor deposition (PECVD) method to prepare a high-quality germanium film, that is, the second absorption active area film; photolithography of the deposited germanium film area, Implement pattern transfer and then etching to form a ridge-type germanium waveguide structure;

(2) Perform P++ doping, N++ doping, P+ doping, and N+ doping on the ridge type germanium waveguide structure in sequence to form the second P++ doped region 9, the second N++ doped region 13, and the second P+ doped region respectively. Region 10, the second N+ doped region 12, and an undoped germanium intrinsic region, that is, the second intrinsic I region 11, is retained to form a second absorption active region;

(3) Deposit a silicon dioxide material layer and use chemical mechanical polishing technology to achieve planarization; open a window with photolithography, and use the low-pressure chemical vapor deposition (LPCVD) method at an appropriate position to prepare a silicon nitride thin film material. A groove structure is etched on the silicon film material to form a light transmission waveguide area 2;

(4) Deposit a silicon dioxide material layer; deposit metal through-hole materials after photolithography and etching to form metal through-holes 15;

(5) Use plasma enhanced chemical vapor deposition (PECVD) to prepare polysilicon material, that is, the first absorption active area material; photolithography of the deposited polysilicon area, pattern transfer and then etching to form a ridge silicon waveguide structure;

(6) Perform P++ doping, N++ doping, P+ doping, and N+ doping on the ridge silicon waveguide structure in sequence to form the first P++ doped region 3, the first N++ doped region 7, and the first P+ doped region respectively. Region 4, the first N+ doped region 6, and retains the undoped silicon intrinsic region structure, that is, the first intrinsic I region 5, forming the first absorption active region;

(7) Open windows by photolithography, and deposit metal materials on the first P++ doped region 3 and the second P++ doped region 9 respectively to form the first metal electrode 8 and the second metal electrode 14.

The above embodiments are only for illustrating the technical concepts and features of the present invention. Their purpose is to enable those familiar with this technology to understand the content of the present invention and implement it accordingly, and cannot limit the scope of protection of the present invention. All equivalent transformations or modifications made based on the spirit and essence of the present invention shall be included in the protection scope of the present invention.

Claims (10)

1. A photodetector integrated with dual absorption areas, characterized in that it includes a substrate (1), a second absorption active area, a light transmission waveguide area (2) and a first absorption active area arranged sequentially from bottom to top. source area; The first absorption active region includes a first P++ doped region (3), a first P+ doped region (4), an undoped first intrinsic I region (5), a first N+ doped region and a first P++ doped region (3). Doping region (6) and a first N++ doping region (7), the first P++ doping region (3) is electrically connected to the first metal electrode (8); The second absorption active region includes a second P++ doped region (9), a second P+ doped region (10), an undoped second intrinsic I region (11), a second N+ doped region, and a second P++ doped region (9). Doped region (12) and a second N++ doped region (13), the second P++ doped region (9) is electrically connected to the second metal electrode (14); The first N++ doped region (7) and the second N++ doped region (13) are electrically connected through a metal through hole (15) between them; The first intrinsic I region (5) and the second intrinsic I region (11) are light absorbing materials with different light absorption wavelength bands. 2. The photodetector integrated with dual absorption regions according to claim 1, characterized in that a groove structure is provided in the middle of the light transmission waveguide region (2). 3. The photodetector integrated with double absorption regions according to claim 1, characterized in that the width w1 of the first intrinsic I region (5) is 50~500nm; And/or, the width w2 of the second intrinsic I region (11) is 50~500nm. 4. The photodetector integrated with double absorption regions according to claim 1, characterized in that part of the first P+ doped region (4), the first intrinsic I region (5) and part of the The first N+ doped region (6) forms a first light absorption region; part of the second P+ doped region (10), the second intrinsic I region (11) and part of the second N+ doped region The region (12) forms a second light absorption region; the light transmission waveguide region (2) is located between the first light absorption region and the second light absorption region. 5. The photodetector integrated with dual absorption areas according to claim 4, characterized in that the distance h1 between the light transmission waveguide area (2) and the first light absorption area is 50~400nm; And/or, the distance h2 between the light transmission waveguide region (2) and the second light absorption region is 50~400 nm. 6. The photodetector integrated with double absorption regions according to claim 1, characterized in that the first P++ doped region (3), the second P++ doped region (9), the third The doping concentrations of an N++ doped region (7) and the second N++ doped region (13) are 1×10 ²⁰ /cm ³ ~8×10 ²⁰ /cm ³ respectively; And/or, the first P+ doped region (4), the second P+ doped region (10), the first N+ doped region (6) and the second N+ doped region (12 ), the doping concentrations are 1×10 ¹⁸ /cm ³ ~6×10 ¹⁸ /cm ³ respectively. 7. The photodetector integrated with dual absorption regions according to any one of claims 1 to 6, characterized in that the first intrinsic I region (5) is any one of the following light-absorbing materials: germanium , germanium-silicon alloy, Group III and V materials or Group III and V material alloys. 8. The photodetector integrated with dual absorption regions according to any one of claims 1 to 6, characterized in that the second intrinsic I region (11) is any one of the following light-absorbing materials: silicon Or perovskite. 9. The photodetector integrated with dual absorption regions according to any one of claims 1 to 6, characterized in that the substrate (1) is a silicon-on-insulator SOI, which is formed on a silicon substrate (101). Deposited silicon dioxide (102) is formed. 10. The photodetector integrated with dual absorption regions according to any one of claims 1 to 6, characterized in that the material of the light transmission waveguide region (2) is silicon nitride, aluminum nitride or niobium. Lithium acid.