JP5494216B2 - Waveguide type optical device - Google Patents

Description

  The present invention relates to a waveguide type optical device.

  In recent years, a waveguide type optical device having an optical waveguide formed on an SOI (Silicon on Insulator) substrate has attracted attention. Since this optical device can be manufactured by LSI (Large Scale Integration) process technology, it is suitable for mass production.

  The waveguide type optical device includes a ridge structure core formed in a semi-insulating silicon layer on an insulating layer, an n-type slab portion in contact with one side surface of the core, and a p-type slab in contact with the other side surface of the core. Part. In the waveguide type optical device, the amount of carriers supplied to the core by the n-type slab portion and the p-type slab portion is modulated, and the amount of carriers accumulated in the core changes. According to the change in the carrier amount, light propagating through the core (hereinafter referred to as propagation light) is modulated.

JP 2004-325914 A

Klaassen et.al., “Unified apparent bandgap narrowing in n- and p-type silicon,” Solid-state electronics, Elsevier Science, 1992, vol.35, pp.125-129. Soref et.al., “Electrooptical effects in silicon,” IEEE Journal of Quantum Electronics, 1987, vol. 23, pp. 123-129.

  The optical device modulates propagating light by accumulating carriers in the core by pin homojunction. However, it is difficult to accumulate a large amount of carriers in the homozygote. For this reason, the modulation efficiency (or extinction ratio) of the waveguide type optical device formed on the insulating layer is low.

  Accordingly, an object of the present invention is to increase the carrier concentration accumulated in the core of the waveguide type optical device on the insulating layer and increase the modulation efficiency (or extinction ratio).

  In order to achieve the above object, according to a first aspect of the present device, an insulating first cladding layer, a semiconductor optical waveguide layer provided on one surface of the first cladding layer, An insulating second clad layer covering the optical waveguide layer, wherein the optical waveguide layer includes a core extending in one direction, and a first slab portion that is in contact with one side surface of the core and is thinner than the core And a second slab portion that is in contact with the other side surface of the core and is thinner than the core, wherein the first slab portion has an n-type region along the core, and the second slab portion is A p-type region extending along the core, and an n-type impurity and a region between the n-type region and the p-type region so that a band gap is narrower than the n-type region and the p-type region. A waveguide type optical device doped with a p-type impurity is provided.

  According to this device, the carrier concentration accumulated in the core of the waveguide type optical device on the insulating layer can be increased, and the modulation efficiency can be increased.

1 is a plan view of a waveguide type optical device according to a first embodiment. It is sectional drawing along the II-II line of FIG. FIG. 3 is an energy band structure of the optical waveguide layer along the line III-III in FIG. 2. FIG. 6 is a diagram for explaining a relationship between power consumption of an electric signal supplied to the waveguide type optical device of Embodiment 1 and a carrier density of a core. FIG. 6 is a process cross-sectional view illustrating the manufacturing method of the waveguide optical device according to the first embodiment (No. 1). FIG. 9 is a process cross-sectional view illustrating the manufacturing method of the waveguide optical device according to the first embodiment (No. 2). 6 is a plan view of a waveguide type optical device according to a second embodiment. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments, but extends to the matters described in the claims and equivalents thereof. In addition, the same code | symbol is attached | subjected to the corresponding part even if drawings differ, and the description is abbreviate | omitted.

(Embodiment 1)
The waveguide type optical device 2 is a variable attenuator type optical switch that modulates the intensity of output light by attenuating the intensity of input light.

(1) Structure FIG. 1 is a plan view of a waveguide type optical device 2 of the present embodiment. FIG. 2 is a cross-sectional view taken along the line II-II in FIG.

―Waveguide structure―
As shown in FIGS. 1 and 2, the waveguide-type optical device 2 includes an insulating first cladding layer 4, a semiconductor optical waveguide layer 6 provided on one surface of the first cladding layer 4, an optical waveguide, An insulating second cladding layer 8 covering the wave layer 6 is provided. Here, the first cladding layer 4 is an insulating layer provided on one surface of the silicon substrate 10. The silicon substrate 10 and the first cladding layer 4 are a substrate and an insulating layer of the SOI substrate 12, respectively.

By the way, the optical waveguide layer 6 is made of crystalline silicon. On the other hand, the first cladding layer 4 and the second cladding layer 8 are formed of, for example, a SiO ₂ layer having a thickness of 1 μm. Here, the operating wavelength of the waveguide type optical device 2 is 1.3 μm or 1.55 μm. Accordingly, the optical waveguide layer 6 and the cladding layers 4 and 8 are transparent at the operating wavelength. The refractive index of the optical waveguide layer 6 is higher than that of the first cladding layer 4 and the second cladding layer 8. Therefore, the light incident on the waveguide type optical device 2 is confined in the optical waveguide layer 6.

  Next, as shown in FIGS. 1 and 2, the optical waveguide layer 6 has a core 14 extending in one direction (predetermined direction). The optical waveguide layer 6 has a first slab portion 18 that is in contact with one side surface of the core 14 and is thinner than the core 14. Furthermore, the optical waveguide layer 6 has a second slab portion 22 that is in contact with the other side surface of the core 14 and is thinner than the core 14.

  That is, the waveguide type optical device 2 has a ridge structure provided in the optical waveguide layer 6. The light confined in the optical waveguide layer 6 propagates through the convex portion of the ridge structure, that is, the core 14.

  Note that the thickness and width of the core 14 are, for example, 250 nm and 500 nm, respectively. The length L of the core 14 is 1 mm, for example. On the other hand, the thickness of the 1st slab part 18 and the 2nd slab part 22 is 50 nm, for example.

Incidentally, the optical waveguide layer 6 of the present embodiment is formed of crystalline silicon as described above. For this reason, the propagation loss (when no carrier is supplied to the core) is as small as 1 cm ⁻¹ or less. However, the optical waveguide layer 6 can also be formed of amorphous silicon or polycrystalline silicon. However, as is well known, amorphous silicon and multicrystalline silicon strongly scatter light due to their non-uniformity. For this reason, if the optical waveguide layer 6 is formed of amorphous silicon or polycrystalline silicon, transmission loss increases. That is, the material of the optical waveguide layer 6 is preferably a crystalline semiconductor.

―Carrier confinement structure―
As shown in FIG. 2, the first slab portion 18 has an n-type region 16 along the core 14. Moreover, the 2nd slab part 22 has the p-type area | region 20 along the core 14, as shown in FIG.

Here, the n-type region 16 is doped with an n-type impurity (for example, boron) having a concentration of 1 × 10 ¹⁹ cm ⁻³ . The p-type region 20 is doped with a p-type impurity (for example, phosphorus) having a concentration of 1 × 10 ¹⁹ cm ⁻³ .

A region 23 (region surrounded by a thin broken line in FIG. 1) between the n-type region 16 and the p-type region 20 is doped with an n-type impurity (for example, boron) at a concentration of 1 × 10 ¹⁹ cm ^−3. And a p-type impurity (for example, phosphorus) is doped at a concentration of 1 × 10 ¹⁹ cm ⁻³ . That is, the region 23 is doped with n-type impurities and p-type impurities at a high concentration.

  Due to this high concentration doping, the band gap of the region 23 including the core 14 is narrowed. As a result, a double heterojunction is formed, and the concentration of carriers confined (ie, accumulated) in the core 14 is increased.

FIG. 3 shows an energy band structure of the optical waveguide layer 6 along the line III-III in FIG. The horizontal axis is the coordinate along the line III-III. The vertical axis represents the energy of electrons. E _c is the bottom of the conduction band. E _v is the top of the valence band. The wavy lines are the bottom E _c ′ of the conduction band and the top E _v ′ of the valence band before the impurities are doped.

When the n-type impurity concentration is 1 × 10 ¹⁷ cm ⁻³ or less, the impurity level (donor level) is isolated (localized). However, when the concentration of the n-type impurity becomes higher than 1 × 10 ¹⁷ cm ⁻³ , the donor levels overlap with each other, and a continuous energy level is formed in the vicinity of the bottom of the conduction band (that is, the donor level is reduced). Delocalized). This forms a miniband and lowers the bottom of the conduction band. Similarly, when the concentration of the p-type impurity is higher than 1 × 10 ¹⁷ cm ⁻³ , the acceptor level is delocalized and the top of the valence band is increased.

By the way, in the present embodiment, the region 23 including the core 14 is doped with 1 × 10 ¹⁹ cm ⁻³ (> 1 × 10 ¹⁷ cm ⁻³ ) n-type and p-type impurities. Therefore, as shown in FIG. 3, the band gap E _{g1 of the} region 23 is narrower than the band gap E _g2 of the n-type region 16 and the band gap E _g3 of the p-type region 20. That is, the optical waveguide layer 6 is formed with a double heterojunction sandwiching the region 23.

  That is, in the present embodiment, the region 23 including the core 14 is doped with n-type impurities and p-type impurities so that the band gap is narrower than that of the n-type region 16 and the p-type region 20, whereby the optical waveguide layer 6, a double heterojunction is formed.

Incidentally, when the concentrations of n-type and p-type impurities are both 1 × 10 ¹⁸ cm ⁻³ , the narrowing of the silicon band gap is 30 meV. Further, when the concentrations are both 1 × 10 ¹⁹ cm ⁻³ and 1 × 10 ²⁰ cm ⁻³ , the narrowing of the band gap of silicon is 60 meV and 90 meV, respectively (see Non-Patent Document 1).

The band gap reduction width increases as the impurity concentration increases. However, if the impurity concentration becomes too high, carrier compensation described later becomes difficult. Accordingly, the concentration of the n-type impurity in the region 23 is preferably 1 × 10 ¹⁸ cm ⁻³ or more and 1 × 10 ²⁰ cm ⁻³ or less, more preferably 5 × 10 ¹⁸ cm ⁻³ or more and 5 × 10 ¹⁹ cm ⁻³ or less. . The same applies to the concentration of the p-type impurity.

In the present embodiment, since the n-type region 16 is also doped with a 1 × 10 ¹⁹ cm donor, its band gap E _g2 is also narrowed. However, this reduction (narrowing) of the band gap is due to a decrease in the bottom of the conduction band, and does not hinder the confinement of carriers (holes). Similarly, the band gap E _g3 of the p-type region 20 is also narrowed. However, since the reduction of the band gap is due to the rise of the top of the valence band, confinement of carriers (electrons) is not hindered.

―Carrier compensation structure―
The region 23 including the core 14 is doped with n-type impurities and p-type impurities having the same concentration. Therefore, the carrier concentration of the n-type impurity in the region 23 is compensated by the carrier concentration of the p-type impurity (that is, the carrier of the n-type impurity in the region 23 is compensated by the p-type impurity). Therefore, almost no carriers are present in the region 23 including the core 14 (that is, the region 23 is semi-insulated). For this reason, the light propagating through the core 14 hardly receives free carrier absorption. For this reason, the propagation loss (waveguide loss) of light propagating through the core 14 becomes 1 cm ⁻¹ or less (however, as will be described later, carriers are supplied from the n-type region 16 and the p-type region 20 to the core 14. Then, transmission loss becomes high.)

Here, the n-type impurity concentration and the p-type impurity concentration in the region 23 do not have to be exactly the same. For example, if the concentration difference between the n-type impurity and the p-type impurity is 2 × 10 ¹⁷ cm ⁻³ or less, the free carrier absorption loss is 3 cm ^−1, which is not a problem. Incidentally, the waveguide loss of the silicon ridge waveguide does not become about 1 cm ⁻¹ or less due to the shape fluctuation.

If the concentration difference between the n-type impurity and the p-type impurity is 1 × 10 ¹⁷ cm ⁻³ or less, the free carrier absorption loss is 1.5 cm ⁻¹ . That is, the concentration difference between the n-type impurity and the p-type impurity is preferably 2 × 10 ¹⁷ cm ⁻³ or less, and more preferably 1 × 10 ¹⁷ cm ⁻³ or less.

  By the way, the region 24 between the n-type region 16 and the core 14 separates the n-type region 16 from the core 14 and prevents attenuation of propagating light due to free carrier absorption of the n-type region 16. Similarly, the region 26 between the p-type region 20 and the core 14 separates the p-type region 20 from the core 14 and prevents attenuation of propagating light due to free carrier absorption in the p-type region 20. The widths of these regions 24 and 26 are preferably 200 to 300 nm, which is about the same as the spread of propagating light. However, when free carrier absorption by the n-type region 16 and the p-type region 20 does not become a problem, these regions need not be provided.

―Electrode structure―
As shown in FIG. 2, the waveguide type optical device 2 is provided on the surface of the first internal electrode 28 provided on one surface of the n-type region 16 and the second clad layer 8, and the first interlayer electrode A first external electrode 30 connected to the first internal electrode 28 through a wiring 36 is provided.

  Similarly, the waveguide type optical device 2 is provided on the surface of the second internal electrode 32 provided on one surface of the p-type region 20 and the second cladding layer 8 as shown in FIG. A second external electrode 34 connected to the second internal electrode 32 through two interlayer wirings 38 is provided.

(2) Operation Next, the operation of the waveguide type optical device (variable attenuator type optical switch) 2 will be described.

  First, light having a wavelength of 1.3 μm (or 1.55 μm) is input to the input port 48 of the waveguide type optical device 2 and propagates through the core 14. In this state, an electrical signal is applied between the n-type region 16 and the p-type region 20 via the external electrode 30 and the external electrode 34, and the intensity of light propagating through the core 14 (propagating light) is modulated. Then, the modulated propagation light is output from the output port 50.

  When an electrical signal is applied between the n-type region 16 and the p-type region 20, electrons are supplied from the n-type region 16 to the core 14, and holes are supplied from the p-type region 20 to the core 14. The carriers (electrons and holes) are accumulated in the double heterojunction 27 described with reference to FIG. The light propagating through the core 14 is attenuated by the free carrier absorption loss due to the accumulated carriers. That is, the carrier concentration of the core 14 changes according to the electric signal, and the intensity of the propagation light changes. Therefore, the waveguide type optical device 2 can be used as a light intensity modulator. Alternatively, the waveguide type optical device 2 can be used as a variable optical attenuator by appropriately changing the voltage applied between the n-type region 16 and the p-type region 20.

  FIG. 4 is a diagram for explaining the relationship between the power consumption of the electrical signal supplied to the waveguide type optical device 2 and the carrier density of the core 14. The horizontal axis represents power consumption per 1 mm element length. The vertical axis represents the carrier density of the core 14 (the density of each of electrons and holes). In FIG. 4, for comparison, the carrier density when the region 23 including the core 14 is not doped with impurities (hereinafter referred to as a comparative example) is indicated by a broken line. FIG. 4 shows a relationship obtained by a simulation program for analyzing carrier conduction in the semiconductor device.

As shown in FIG. 4, according to the present embodiment, the carrier density 40 is higher than the carrier density 42 of the comparative example. For example, when the power consumption is 16 mW, the carrier density 40 of the present embodiment is 2.2 × 10 ¹⁸ cm ⁻³ . On the other hand, the carrier concentration of the comparative example is 1.0 × 10 ¹⁸ cm ⁻³ . That is, according to the present embodiment, the carrier density is 2.2 times, and as a result, the free carrier absorption loss is 2.2 times.

It is known that the free carrier absorption loss Δα (cm ⁻¹ ) can be expressed by the following equation.

Δα = 8.5 × 10 ^-18 × n + 6.0 × 10 ^-18 × p (1)
Here, n and p are the densities of electrons and holes, respectively (units of n and p are cm ⁻³ ). In this embodiment, since n and p are equal, the absorption loss Δα (cm ⁻¹ ) is expressed by the following equation.

Δα = 14.5 × 10 ^-18 × N (2)
Here, N is the carrier density (= n = p) shown on the vertical axis of FIG.

According to equation (2), the extinction ratio of propagating light (percentage of output light intensity when voltage is applied and when voltage is not applied) at a power consumption of 16 mW (per element length of 1 mm) is 1 as the light confinement factor of the core 14. Then, it becomes 13.9 dB (Δα = 14.5 cm ⁻¹ ). On the other hand, the extinction ratio of the comparative example under the same conditions is 6.3 dB. That is, according to the present embodiment, the extinction ratio of the variable attenuator type optical switch 2 is increased.

  By the way, it is known that the coefficients of the carrier density n and p in the formula (1) are inversely proportional to the movement of electrons and holes, respectively (Non-patent Document 2). In the present embodiment, since the core 14 is doped with an impurity at a high concentration, the movement of electrons and holes becomes small. Therefore, the coefficient of the carrier density n, p is larger than that of the expression (1). For this reason, the actual extinction ratio of this waveguide type optical device 2 becomes larger than the said value.

(3) Manufacturing Method FIGS. 5 and 6 are process cross-sectional views illustrating a method of manufacturing the waveguide type optical device 2.

  First, the silicon layer of the SOI substrate 12 is processed by photolithography and dry etching to form the optical waveguide layer 6 having the core 14.

  Next, as shown in FIG. 5A, a photoresist film 44a is formed at the position where the n-type region 16 is formed.

Next, as shown in FIG. 5B, a p-type dopant (for example, phosphorus) is ion-implanted into the optical waveguide layer 6 using the photoresist film 44a as a mask. The ion implantation is performed under the condition that the p-type impurity concentration in the optical waveguide layer 6 is 1 × 10 ¹⁹ cm ⁻³ . Thereby, the p-type dopant implantation region 46 including the core 14 is formed. Thereafter, the photoresist film 44a is removed.

  Next, as shown in FIG. 5C, a photoresist film 44b is formed at the position where the p-type region 20 is formed.

Next, as shown in FIG. 6A, n-type dopant (for example, boron) is ion-implanted into the optical waveguide layer 6 using the photoresist film 44b as a mask. The ion implantation is performed under the condition that the n-type impurity concentration in the optical waveguide layer 6 is 1 × 10 ¹⁹ cm ⁻³ . Thereafter, the photoresist film 44b is removed, and a heat treatment for activating the impurities is performed. Thus, the n-type region 16, the p-type region 20, and the region 23 doped with n-type impurities and p-type impurities are formed.

Next, as shown in FIG. 6B, internal electrodes 28 and 32 are formed on the surfaces of the n-type region 16 and the p-type region 20, respectively. Thereafter, a SiO ₂ film is deposited on the surface of the optical waveguide layer 6 by, for example, a CVD (Chemical Vapor Deposition) method to form the second cladding layer 8.

  Next, as shown in FIG. 6C, interlayer wirings 36 and 38 and external electrodes 30 and 34 are formed in the second cladding layer 8. Thereafter, the SOI substrate 12 is divided into individual chips to complete the waveguide type optical device 2.

(Embodiment 2)
The waveguide type optical device 52 is a Mach-Zehnder interferometer type optical switch that modulates input light by changing the phase of branched light by the plasma effect.

(1) Structure FIG. 7 is a plan view of the waveguide type optical device 52 of the present embodiment.

  As shown in FIG. 7, the waveguide type optical device 52 has a branching device 58 for branching the light input to the first input port 48a into the first branched light 54 and the second branched light 56. Yes. The branching device 58 is a 2-mode 2-output multimode interference waveguide (Multi Mode Interference, MMI).

  Further, the waveguide type optical device 52 includes a first phase modulator 60a on which the first branched light 54 is incident and a second phase modulator 60b on which the second branched light 56 is incident. .

  Further, the waveguide type optical device 52 combines the first branched light 54 emitted from the first phase shifter 60a and the second branched light 56 emitted from the second phase shifter 60b, and A coupler 62 that generates one coupled light 64a and a first coupled light 64b is provided. The coupler 62 is also a 2-input 2-output multimode interference waveguide MMI.

  In addition, the waveguide type optical device 52 has a first output port 50a that outputs the first coupled light 64a and a first output port 50b that outputs the second coupled light 64b.

  Further, the waveguide type optical device 52 has an optical waveguide 66 a that connects the first optical input port 48 a and the branching device 58. The waveguide type optical device 52 includes optical waveguides 66b to 66e that connect the optical elements (the branching device 58, the phase modulators 60a and 60b, and the coupler 62). Further, the waveguide type optical device 52 includes an optical waveguide 66f connecting the coupler 62 and the first optical output port 50a, and an optical waveguide 66g connecting the coupler 62 and the second optical output port 50b. have. The waveguide type optical device 52 includes a second input port 48b and an optical waveguide 66h that connects the second input port 48b and the branching device 58.

Here, each of the optical elements and the optical waveguide is formed in the silicon layer of the SOI substrate. The waveguide type optical device 52 has an insulating clad layer (for example, SiO ₂ ) covering the silicon layer, similarly to the waveguide type optical device 52 of the first embodiment.

  The structures of the first phase modulator 60a and the second phase modulator 60b are substantially the same as those of the variable attenuator type optical switch 2 according to the first embodiment described with reference to FIGS. However, the element lengths of the first and second phase modulators 60a and 60b are shorter than those of the variable attenuator type optical switch 2 of the first embodiment. For example, the element lengths of the first and second phase modulators 60a and 60b are 100 to 200 μm.

  The branching device 58, the coupler 62, and the optical waveguides 66a to 66h have substantially the same waveguide structure as the variable attenuator type optical switch 2 of the first embodiment. However, these optical elements are not doped with impurities. The cores of the branching device 58 and the coupler 62 have a width wider than the core of the variable attenuator type optical switch 2 of the first embodiment.

(2) Operation Next, the operation of the waveguide type optical device (Mach-Zehnder interferometer type optical switch) 52 will be described.

  The operating wavelength of the waveguide type optical device 52 is, for example, 1.3 μm or 1.55 μm. The light incident on the first input port 48a propagates through the optical waveguide 66a and enters the optical branching device 58. The light incident on the optical branching device 58 is branched into a first branched light 54 and a second branched light 56. The first branched light 54 and the second branched light 56 propagate through the optical waveguides 66b and 66c and enter the first phase modulator 60a and the second phase modulator 60b, respectively.

  The first branched light 54 incident on the first phase modulator 60a is phase-modulated and then emitted from the first phase modulator 60a. On the other hand, after the phase of the second branched light 56 incident on the second phase modulator 60b is adjusted so that the optical length of the propagation path is substantially the same as that of the first branched light 54 (when not modulated). The light is emitted from the second phase modulator 60b.

  The first branched light 54 emitted from the first phase modulator 60 a and the second branched light 56 emitted from the second phase modulator 60 b propagate through the optical waveguides 66 d and 66 e and enter the optical coupler 62. Incident. The first branched light 54 and the second branched light 56 incident on the optical coupler 62 are combined into a first combined light 64a and a second combined light 64b. Thereafter, the first coupled light 64a propagates through the optical waveguide 66f and is output from the first output port 50a. Similarly, the second coupled light 64b propagates through the optical waveguide 66g and is output from the second output port 50b.

  Here, in the first phase modulator 60a, an electric signal is applied between the n-type region 16 and the p-type region 20 via the external electrodes 30a and 34a, and the plasma effect of the carriers accumulated in the core 14 is obtained. Thus, the phase of the first branched light 54 propagating through the core 14 is modulated. The amount of change in phase is, for example, 0 or π (rad).

  On the other hand, in the second phase modulator 60b, a predetermined voltage is applied between the n-type region 16 and the p-type region 20 via the external electrodes 30b and 34b. Here, the second phase modulator 60b is configured so that the optical length of the propagation path of the first branched light 54 and the optical length of the propagation path of the second branched light 56 during non-modulation are substantially the same. The phase of the second branched light 56 is adjusted. Accordingly, the first combined light 64a and the second combined light 64b blink according to the electrical signal applied to the first phase modulator 60a.

  The blinking timing of the first combined light 64a and the second combined light 64b is shifted by a half cycle. Therefore, one or both of the first combined light 64a and the second combined light 64b can be used as output light.

  The first phase modulator 60a and the second phase modulator 60b of the present embodiment have the same carrier confinement structure as the variable attenuator type optical switch 2 of the first embodiment. Therefore, the density of carriers confined in the core 14 is higher than when the region 23 between the n-type region 16 and the p-type region 20 is not doped with impurities. As a result, the refractive index change due to the plasma effect increases and the phase modulation efficiency increases.

As described in the first embodiment, when a power of 16 mW per 1 mm of element length is input, the carrier density confined in the core 14 is 2.2 times higher than when the region 23 is not doped with impurities. Therefore, the element lengths of the first phase modulator 60a and the second phase modulator 60b can be reduced to 1 / 2.2. Incidentally, the refractive index change in this case is −5.9 × 10 ⁻³ .

  As described above, the optical branching device 58 and the optical coupler 62 of the present embodiment are MMIs. However, the optical splitter 58 and the optical coupler 62 may be other optical elements such as a directional coupler and a Y-branch waveguide. The waveguide type optical device 52 has two phase modulators. However, there may be only one phase modulator.

  In the present embodiment, the phase modulators 60 a and 60 b are part of the Mach-Zehnder interferometer type optical switch 58. However, the phase modulators 60a and 60b can also be used as a single optical device.

  In the above embodiment, the optical waveguide layer 6 is crystalline silicon. However, the optical waveguide layer 6 may be another crystalline semiconductor layer, for example, a crystalline GaAs layer or a crystalline InP layer.

  In the above embodiment, the optical waveguide layer 6 is formed on the silicon layer of the SOI substrate. However, a silicon layer may be provided on another substrate, for example, a quartz substrate, and the optical waveguide layer 6 may be formed on the silicon layer.

In the above embodiment, the first cladding layer 4 and the second cladding layer 8 are SiO ₂ layers. However, the first cladding layer 4 and the second cladding layer 8 may be other insulating layers, for example, a silicon oxynitride layer (SiNO layer) or a silicon nitride layer (SiN layer).

  In the above embodiment, only the optical waveguide and the optical element are provided in the silicon layer of the SOI substrate. However, an electronic circuit such as a drive circuit for the waveguide type optical devices 2 and 52 may be formed on the silicon layer of the SOI substrate.

  Regarding the above embodiment, the following additional notes are disclosed.

(Appendix 1)
An insulating first cladding layer;
A semiconductor optical waveguide layer provided on one surface of the first cladding layer;
An insulating second cladding layer covering the optical waveguide layer;
The optical waveguide layer includes a core extending in one direction, a first slab portion that is in contact with one side surface of the core and is thinner than the core, and a second slab that is in contact with the other side surface of the core and is thinner than the core. And
The first slab portion has an n-type region along the core,
The second slab portion has a p-type region along the core,
A region between the n-type region and the p-type region is doped with an n-type impurity and a p-type impurity such that a band gap is narrower than that of the n-type region and the p-type region. device.

(Appendix 2)
In the waveguide type optical device according to attachment 1,
Further, the carrier concentration of the n-type impurity in the region is compensated by the carrier concentration of the p-type impurity.
A waveguide-type optical device.

(Appendix 3)
In the waveguide type optical device according to appendix 1 or 2,
Furthermore, an electrical signal is applied between the n-type region and the p-type region, and the intensity of light propagating through the core is modulated.
A waveguide-type optical device.

(Appendix 4)
In the waveguide type optical device according to appendix 1 or 2,
Furthermore, an electrical signal is applied between the n-type region and the p-type region, and the phase of light propagating through the core is modulated.
A waveguide-type optical device.

(Appendix 5)
An insulating first cladding layer;
A semiconductor optical waveguide layer provided on one surface of the first cladding layer;
An insulating second cladding layer covering the optical waveguide layer;
The optical waveguide layer includes a core extending in one direction, a first slab portion that is in contact with one side surface of the core and is thinner than the core, and a second slab that is in contact with the other side surface of the core and is thinner than the core. And
The first slab portion has an n-type region along the core,
The second slab portion has a p-type region along the core,
A region between the n-type region and the p-type region is doped with an n-type impurity at a concentration of 1 × 10 ¹⁸ cm ^{−3 to} 1 × 10 ²⁰ cm ⁻³ and 1 × 10 ¹⁸ cm ^−3. A waveguide type optical device doped with a p-type impurity at a concentration of 1 × 10 ²⁰ cm ⁻³ or less.

(Appendix 6)
In the waveguide type optical device according to attachment 5,
Furthermore, the concentration difference between the n-type impurity and the p-type impurity in the region is 2 × 10 ¹⁷ cm ⁻³ or less.
A waveguide-type optical device.

2... Waveguide type optical device 4 according to Embodiment 1... First cladding layer 6... Optical waveguide layer 8... Second cladding layer 14. Region 18 ... first slab portion 20 ... p-type region 22 ... second slab portion 23 ... region 52 between n-type region and p-type region ... of the second embodiment Waveguide type optical device

Claims (4)

An insulating first cladding layer;
An optical waveguide layer provided on one surface of the first cladding layer;
An insulating second cladding layer covering the optical waveguide layer;
The optical waveguide layer has a core which is formed by extending Mashimashi semiconductor in one direction, and one of less than tangent pre SL core formed by the semiconductor to side first slab portion of the core, the core and a thin second slab portion from the previous SL core formed by the semiconductor and against the other side,
The first slab portion has an n-type region along the core,
The second slab portion has a p-type region along the core,
In the region between the n-type region and the p-type region, the energy of the bottom of the conduction band in the region is lower than the first energy value from the first energy value of the bottom of the conduction band in the p-type region. The n-type impurity is doped so as to change to a two-energy value, and the energy at the top of the valence band in the region is greater than the third energy value from the third energy value at the top of the valence band in the n-type region. A p-type impurity is doped to change to a high fourth energy value,
A waveguide-type light modulation device in which carriers are supplied to the core from the n-type region and the p-type region, and at least the intensity or phase of light propagating through the core is modulated. The waveguide- type light modulation device according to claim 1,
Further, the carrier concentration of the n-type impurity in the region is compensated by the carrier concentration of the p-type impurity.
A waveguide- type light modulation device . An insulating first cladding layer;
An optical waveguide layer provided on one surface of the first cladding layer;
An insulating second cladding layer covering the optical waveguide layer;
The optical waveguide layer has a core which is formed by extending Mashimashi semiconductor in one direction, and one of less than tangent pre SL core formed by the semiconductor to side first slab portion of the core, the core and a thin second slab portion from the previous SL core formed by the semiconductor and against the other side,
The first slab portion has an n-type region along the core,
The second slab portion has a p-type region along the core,
In the region between the n-type region and the p-type region, the energy of the bottom of the conduction band in the region is lower than the first energy value from the first energy value of the bottom of the conduction band in the p-type region. N-type impurities are doped at a concentration of 1 × 10 ¹⁸ cm ⁻³ or more and 1 × 10 ²⁰ cm ⁻³ or less so as to change into two energy values, and the energy value at the top of the valence band in the region is At a concentration of 1 × 10 ¹⁸ cm ⁻³ or more and 1 × 10 ²⁰ cm ⁻³ or less so as to change from the third energy value at the top of the valence band in the n-type region to a fourth energy value higher than the third energy value. doped with p-type impurities ,
A waveguide-type light modulation device in which carriers are supplied to the core from the n-type region and the p-type region, and at least the intensity or phase of light propagating through the core is modulated. The waveguide- type light modulation device according to claim 3,
Furthermore, the concentration difference between the n-type impurity and the p-type impurity in the region is 2 × 10 ¹⁷ cm ⁻³ or less.
A waveguide- type light modulation device .

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