Top-injection electro-optic modulation structure

Abstract

The present invention discloses a top injection electro-optic modulation structure. The top injection electro-optic modulation structure includes a SiO2 buried oxide layer. On the SiO2 buried oxide layer, two N++ well regions and a Si flat layer are covered. The two N++ well regions are located on both sides of the Si flat layer. In the middle of the Si flat layer, a waveguide region is covered. On the upper part of the waveguide region, a P++ well region is covered. A cathode electrode is connected to each N++ well region. The regions other than the cathode electrode covered on the N++ well region, the cathode electrode, the P++ well region, and the regions other than the waveguide region covered on the Si flat layer are all covered with a SiO2 covering layer. By performing P-type heavy doping at the ridge top and N-type heavy doping on the flat layer, a novel p-i-n electro-optic modulation structure with top injection is formed, which improves carrier injection and enhances the plasma dispersion effect.

Description

Technical Field

[0001] The invention belongs to the technical field of silicon-based photonic devices, and in particular relates to a top-injection electro-optic modulation structure. Background Art

[0002] In recent years, with the advancement of optoelectronic technology, silicon-based modulators have entered the micro-nano size. Silicon-based electro-optical modulators can transmit single-mode light waves, have the advantages of high speed, low loss and small size, and are compatible with integrated circuit manufacturing processes. They have now become the core of silicon-based optoelectronic devices.

[0003] The plasma dispersion effect changes the refractive index and absorption coefficient by changing the free carrier concentration in the optical waveguide. The plasma dispersion effect of silicon-based materials is very significant and can achieve high-speed optical waveguide modulation. It is the main working basis of current silicon-based electro-optic modulators. However, the existing silicon-based electro-optic modulators based on plasma dispersion are optimized by changing the structure of the doped region to reduce the absorption loss of carriers, which will increase the challenge of CMOS compatibility. Summary of the invention

[0004] The purpose of the present invention is to provide a top-injected electro-optical modulation structure, which forms a new top-injected pin electro-optical modulation structure by heavily doping the top of the ridge with P type and heavily doping the planar layer with N type, thereby improving carrier injection and enhancing the plasma dispersion effect.

[0005] The technical solution adopted by the present invention is a top-injected electro-optical modulation structure, including a SiO2 buried oxide layer, the SiO2 buried oxide layer is covered with two N++ well regions and a Si planar layer, the two N++ well regions are located on both sides of the Si planar layer, the middle part of the Si planar layer is covered with a waveguide region, the upper part of the waveguide region is covered with a P++ well region, the P++ well region is connected to an anode electrode, each N++ well region is connected to a cathode electrode, the area covered on the N++ well region other than the cathode electrode, the anode electrode, the cathode electrode, the P++ well region, and the area covered on the Si planar layer other than the waveguide region are all covered with a SiO2 covering layer.

[0006] The present invention is also characterized in that:

[0007] The material of the waveguide region is SiGe, the waveguide width is 420nm, and the sum of the heights of the waveguide region and the P++ well region is 130nm.

[0008] The Si slab layer height is 90nm.

[0009] The doping concentration of the P++ well region is 1×10 20 cm -3 ~5×10 20 cm -3 , the dopant is B ion; the height of the P++ well region is 1~100nm and the width is 420nm.

[0010] The doping concentration of the N++ well region is 1×10 20 cm -3 ~5×10 20 cm -3 , the dopant is P ions; the height of the N++ well region is 90nm and the width is 1μm.

[0011] The distance between the N++ well region and the waveguide region boundary is 1 μm.

[0012] The beneficial effects of the present invention are:

[0013] (1) The top-injected electro-optic modulator structure of the present invention sets the heavily doped P++ well region on the top of the waveguide region, and the N++ well region is set on both sides of the slab layer. The heterojunction modulator concentration formed by the P++ well region and the waveguide region materials is significantly greater than the carrier concentration of the silicon-based modulator. Moreover, the greater the forward bias voltage, the greater the difference in carrier concentration between the two, thereby increasing the carrier injection concentration in the modulation region and being more conducive to electro-optic modulation.

[0014] (2) The top injection electro-optic modulator structure of the present invention only needs to change the heavily doped region. The anode electrode is at the top of the waveguide region. The distance from the heavily doped region to the waveguide region is small. A smaller voltage can achieve carrier injection. No additional process is required. It is easy to implement and is an ideal new electro-optic modulator.

[0015] (3) The top-injected electro-optic modulator structure of the present invention reduces the driving voltage required for 20 dB attenuation of the modulator from 1.24 V to 0.99 V, and the modulation efficiency is about 1.25 times that of the silicon-based modulator, thereby improving carrier injection and enhancing the plasma dispersion effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 It is a schematic diagram of the structure of the top injection electro-optic modulator of the present invention;

[0017] Figure 2 It is a schematic diagram of the structure of a conventional PIN electro-optic modulator;

[0018] Figure 3 This is a comparison graph of carrier concentrations between Si waveguide and SiGe waveguide electro-optical modulators;

[0019] Figure 4 It is the comparison curve of bias voltage and attenuation of Si waveguide and SiGe waveguide electro-optical modulator;

[0020] In the figure, 1. SiO2 buried oxide layer, 2. N++ well region, 3. Si planar layer, 4. waveguide region, 5. P++ well region, 6. cathode electrode, 7. SiO2 covering layer; 8. N-Sub type substrate, 9. P+ well region, 10. N+ well region, 11. intrinsic N-type silicon modulation region, 12. first cathode electrode, 13. second cathode electrode, 14. SiO2 covering layer a, 15. SiO2 buried layer a, 16. Si planar layer a, 17. anode electrode. DETAILED DESCRIPTION

[0021] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] The top injection electro-optic modulation structure of the present invention is as follows: Figure 1 As shown, it includes a SiO2 buried oxide layer 1, the SiO2 buried oxide layer 1 covers two N++ well regions 2 and a Si flat layer 3, the two N++ well regions 2 are separated on both sides of the Si flat layer 3, the middle part of the Si flat layer 3 covers a waveguide region 4, the upper part of the waveguide region 4 covers a P++ well region 5, the P++ well region 5 is connected to an anode electrode 17, each N++ well region 2 is connected to a cathode electrode 6, and the N++ well region 2 covers an area other than the cathode electrode 6, an anode electrode 17, a cathode electrode 6, a P++ well region 5, The area other than the waveguide area 4 on the Si slab layer 3 is covered with a SiO2 covering layer 7. The heavily doped P++ well area 5 is set on the top of the waveguide area 4, and the N++ well area 2 is set on both sides of the Si slab layer 3. The distance from the top-injected heavily doped area to the waveguide area 4 is small, and a smaller voltage can achieve carrier injection, improve the carrier injection efficiency, and increase the carrier concentration. The material of the waveguide area 4 is SiGe, the waveguide width is 420nm, and the height of the waveguide area 4 and the P++ well area 5 is 130nm. The height of the Si slab layer 3 is 90nm. The doping concentration of the P++ well area 5 is 1×10 20 cm -3 ~5×10 20 cm -3 , the dopant is B ion; the height of the P++ well region is 1-100nm and the width is 420nm. The doping concentration of the N++ well region 2 is 1×10 20 cm -3 ~5×10 20 cm -3 The dopant is P ions; the height of the N++ well region is 90nm and the width is 1μm. The distance between the boundary of the N++ well region 2 and the waveguide region 4 is 1μm.

[0023] The carrier concentration of SiGe / Si heterojunction modulator is significantly greater than that of silicon-based modulator, and the greater the forward bias voltage, the greater the difference in carrier concentration between the two, which increases the carrier injection concentration in the modulation area and is more conducive to electro-optical modulation; during the manufacturing process, only the heavily doped area needs to be changed, the anode electrode 17 is at the top of the waveguide area 4, the distance from the heavily doped area to the waveguide area 4 is small, and a smaller voltage can achieve carrier injection. It does not require additional processes and is easy to implement, making it an ideal new electro-optical modulator.

[0024] For the conventional PIN modulator structure, it is mainly composed of silicon materials; the conventional PIN modulator structure is as follows Figure 2 As shown, an N-Sub type substrate 8 is used, and a SiO2 buried layer a15 is arranged above the N-Sub type substrate 8, and an intrinsic N-type silicon modulation area 11, a P+ well area 9, and an N+ well area 10 are respectively arranged above the SiO2 buried layer a15. The P+ well area 9 and the N+ well area 10 are respectively located on both sides of the intrinsic N-type silicon modulation area 11, a first cathode electrode 12 is arranged on the P+ well area 9, and a second cathode electrode 13 is arranged on the N+ well area 10. The first cathode electrode 12, the second cathode electrode 13 and the intrinsic N-type silicon modulation area 11 are covered with a SiO2 covering layer a14.

[0025] according to Figure 1 , Figure 2 By comparison, it can be seen that the top injection electro-optic modulator structure of the present invention is different from the conventional PIN modulator structure in that in the top injection electro-optic modulator structure of the present invention, the heavily doped P++ well region 5 is placed on the top and the N++ well region 2 is placed at both ends, the anode electrode 17 is at the top of the waveguide region 4, the distance from the heavily doped region to the waveguide region 4 is small, and a smaller voltage can achieve carrier injection, thereby increasing the carrier injection concentration in the modulation region.

[0026] The working principle of the top injection electro-optical modulation structure of the present invention is:

[0027] When a positive voltage is applied to the anode electrode 17 and a negative voltage is applied to the cathode electrode 6, the electro-optic modulator can be controlled to be turned on, and holes and electrons are injected from the P++ well region 5 and the N++ well regions 2 on both sides into the waveguide region 4. The change in the number of carriers will cause the refractive index of the waveguide region to change, thereby achieving the purpose of light wave modulation. Due to the top injection, the distance from the heavily doped region to the waveguide region is small, which improves the carrier injection efficiency and increases the carrier injection concentration, which is more conducive to electro-optic modulation.

[0028] Example

[0029] Prepare a top-injection electro-optical modulation structure, in which the doping concentration of the P++ well region 5 is 3×10 20 cm -3, the dopant is B ion; the height of the P++ well region is 50nm, the width is 420nm, and the doping concentration of the N++ well region 2 is 3×10 20 cm -3 .

[0030] The top injection electro-optic modulator and conventional PIN modulator structures are simulated in ISE TCAD. The horizontal axis is the forward bias voltage and the vertical axis is the carrier concentration. The results are as follows: Figure 3 As shown, according to Figure 3 It can be seen that when the forward bias voltage is greater than 0.6V, the carrier concentration of the SiGe / Si heterojunction modulator is significantly greater than that of the silicon-based modulator, and the greater the forward bias voltage, the greater the difference in carrier concentration between the two. This is because there is an energy band offset between Si and SiGe in the SiGe / Si heterojunction modulator, and the carriers are confined in the SiGe layer, so the carrier concentration in the SiGe layer is greater than that in the Si layer.

[0031] The top injection electro-optic modulator and conventional PIN modulator structures are simulated in ISE TCAD. The horizontal axis is the forward bias voltage and the vertical axis is the attenuation (dB). The results are as follows: Figure 4 As shown, according to Figure 4 It can be seen that the relationship curve between the bias voltage and attenuation of the SiGe / Si heterojunction modulator and the silicon-based modulator is shown. The horizontal axis in the figure represents the forward bias voltage of the modulator, and the vertical axis represents the attenuation of the modulator. It can be seen from the figure that with the increase of the forward bias voltage, the attenuation of the two modulators gradually increases. Compared with the performance of the silicon-based modulator, the driving voltage required for the 20dB attenuation of the SiGe / Si heterojunction modulator is reduced from 1.24V to 0.99V, and the modulation efficiency of the SiGe / Si heterojunction modulator is about 1.25 times that of the silicon-based modulator.

[0032] according to Figure 4 It can be seen that from the perspective of modulator performance, the driving voltage required for 20dB attenuation of the modulator is reduced from 1.24V to 0.99V, and the modulation efficiency is about 1.25 times that of the silicon-based modulator, which improves carrier injection and enhances the plasma dispersion effect.

[0033] Through the above method, the top injection electro-optical modulation structure of the present invention is a top injection electro-optical modulator structure of the present invention. On the basis of the conventional PIN electro-optical modulator structure, the heavily doped P++ well region is set at the top of the waveguide region, and the N++ well region is set on both sides of the flat layer. The carrier concentration of the SiGe / Si heterojunction modulator is significantly greater than that of the silicon-based modulator, and the greater the forward bias voltage, the greater the difference in carrier concentration between the two, which increases the carrier injection concentration in the modulation region and is more conducive to electro-optical modulation; in the manufacturing process, only the heavily doped region needs to be changed, the anode electrode is at the top of the waveguide region, the distance from the heavily doped region to the waveguide region is small, and a smaller voltage can achieve carrier injection. No additional process is required, it is easy to implement, and it is an ideal new electro-optical modulator; from the perspective of modulator performance, the driving voltage required for the 20dB attenuation of the modulator is reduced from 1.24V to 0.99V, and the modulation efficiency is about 1.25 times that of the silicon-based modulator, which improves carrier injection and enhances the plasma dispersion effect.

Claims

1. Top injection electro-optical modulation structure, characterized in that: The invention comprises a SiO2 buried oxide layer (1), wherein the SiO2 buried oxide layer (1) is covered with two N++ well regions (2) and a Si flat layer (3), wherein the two N++ well regions (2) are located on both sides of the Si flat layer (3), wherein the middle part of the Si flat layer (3) is covered with a waveguide region (4), wherein the upper part of the waveguide region (4) is covered with a P++ well region (5), wherein the P++ well region (5) is connected to an anode electrode (17), wherein each of the N++ well regions (2) is connected to a cathode electrode (6), wherein the area covered on the N++ well region (2) other than the cathode electrode (6), the cathode electrode (6), the P++ well region (5), the anode electrode (17), and the area covered on the Si flat layer (3) other than the waveguide region (4) are all covered with a SiO2 covering layer (7); The material of the waveguide region (4) is SiGe, the waveguide width is 420 nm, and the sum of the heights of the waveguide region (4) and the P++ well region (5) is 130 nm; The Si plate layer (3) has a height of 90 nm; The doping concentration of the P++ well region (5) is 1×10 20 cm -3 ~5×10 20 cm -3 , the dopant is B ion; the height of the P++ well region (5) is 1-100 nm and the width is 420 nm; The doping concentration of the N++ well region (2) is 1×10 20 cm -3 ~5×10 20 cm -3 , the dopant is P ion; the height of the N++ well region is 90nm and the width is 1μm; The boundary distance between the N++ well region (2) and the waveguide region (4) is 1 μm.

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