An electro-optic device is provided. The electro-optic device includes a junction layer disposed between a first conductivity type semiconductor layer and a second conductivity type semiconductor layer to which a reverse vias voltage is applied. The first conductivity type semiconductor layer and the second conductivity type semiconductor layer have an about 2 to 4-time doping concentration difference therebetween, thus making it possible to provide the electro-optic device optimized for high speed, low power consumption and high integration.

CROSS-REFERENCE TO RELATED APPLICATIONS

This U.S. non-provisional patent application claims priority under 35 U.S.C. §119 of Korean Patent Application No. 10-2009-0081973, filed on Sep. 1, 2009, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention disclosed herein relates to electro-optic devices, and more particularly, to an electro-optic device including a diode having a reverse bias voltage applied thereto.

With the development of the semiconductor industry, semiconductor integrated circuits (ICs) such as logic devices and memory devices are becoming higher in speed and integration degree. According to the high speed and the high integration degree of semiconductor ICs, the communication speed between semiconductor ICs is connected directly with the performance of an electronic device including the semiconductor ICs. Typically, semiconductor ICs exchange data through electrical communication. For example, semiconductor ICs are mounted on a printed circuit board (PCB) to perform electrical communication therebetween through interconnections included in the PCB. In this case, there is a limitation in reducing the electrical resistances between the semiconductor ICs (e.g., the resistance between an external terminal of the package and a pad of the semiconductor IC, the contact resistance between the package and the PCB, and the interconnection resistance of the PCB). Also, the electrical communication may be affected by external electromagnetic waves. These factors make it difficult to reduce the communication speed between the semiconductor ICs.

SUMMARY OF THE INVENTION

Embodiments of the present invention provide electro-optic devices with an increased operation speed.

Embodiments of the present invention also provide electro-optic devices optimized for high integration.

Embodiments of the present invention also provide electro-optic devices optimized for low power consumption.

In some embodiments of the present invention, electro-optic devices include: a substrate; an optical modulator being disposed on the substrate and including a first conductivity type semiconductor layer, a second conductivity type semiconductor layer, and a junction layer disposed between the first conductivity type semiconductor layer and the second conductivity type semiconductor layer; and a pair of recessed portions extending from the optical modulator and being thinner than the optical modulator, wherein a reverse bias voltage is applied to the first conductivity type semiconductor layer and the second conductivity type semiconductor layer.

In some embodiments, the first conductivity type semiconductor layer includes a P-type doped region and the second conductivity type semiconductor layer includes an N-type doped region, wherein the doping concentration of the P-type doped region is about 2 to 4 times higher than the doping concentration of the N-type doped region.

In other embodiments, the interfaces between the first conductivity type semiconductor layer, the second conductivity type semiconductor layer and the junction layer intersect the upper surface of the substrate.

In further embodiments, the optical modulator includes a first sidewall and a second sidewall extending respectively from the upper surfaces of the recessed portions, wherein the junction layer is disposed between the first sidewall and the second sidewall.

In still further embodiments, the second conductivity type semiconductor layer is spaced apart from the substrate with the first conductivity type semiconductor layer disposed therebetween.

In still further embodiments, the first conductivity type semiconductor layer is thicker than the recessed portions.

In still further embodiments, the junction layer includes a first surface contacting the first conductivity type semiconductor layer and a second surface contacting the second conductivity type semiconductor layer, wherein the first surface is lower than the upper surfaces of the recessed portions and the second surface is higher than the upper surfaces of the recessed portions.

In still further embodiments, the first conductivity type semiconductor layer is thinner than the recessed portions.

In still further embodiments, the optical modulator includes a light-receiving surface receiving a first optical signal and a light-outputting surface outputting a second optical signal, wherein a phase of the second optical signal depends on the level of the reverse bias voltage.

In still further embodiments, the electro-optic devices further include at least one grating coupler connected to at least one of the light-receiving surface and the light-outputting surface of the optical modulator.

In still further embodiments, an optical absorption factor of the junction layer depends on the level of the reverse bias voltage.

In still further embodiments, the electro-optic devices further include a cladding layer disposed between the substrate and the optical modulator.

In still further embodiments, the cladding layer is formed by implanting oxygen ions selectively at a portion for an optical waveguide on the substrate.

In still further embodiments, the cladding layer includes a silicon oxide and the vertical concentration of the silicon oxide has a Gaussian distribution.

In still further embodiments, the substrate includes a switching region spaced apart from the optical modulator, and the electro-optic devices further include: a gate insulating layer disposed on the switching region of the substrate; and a gate electrode disposed on the gate insulating layer.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Since preferred embodiments are provided below, the order of the reference numerals given in the description is not limited thereto. In the drawings, the dimensions of layers and regions may be exaggerated for clarity of illustration. It will be understood that when a layer (or film) is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. As used herein, the term and/or includes any and all combinations of one or more of the associated listed items. Throughout the specification, like reference numerals refer to like elements.

Hereinafter, a description will be given of an electro-optic device according to an embodiment of the present invention.

FIG. 1is a plan view of an electro-optic device according to an embodiment of the present invention. An electro-optic region102ofFIG. 2Ais a sectional view taken along a line I-I′ ofFIG. 1, and a switching region104ofFIG. 2Amay be a peripheral circuit region spaced apart from the electro-optic region102.FIG. 3is a sectional view taken along a line II-II′ ofFIG. 1.

Referring toFIGS. 1,2A and3, a substrate100is provided. The substrate100may be a silicon substrate or a Silicon-On-Insulator (SOI) substrate. The substrate100may include an electro-optic region102and a switching region104.

An electro-optic device150may be disposed on the substrate100of the electro-optic region102. The electro-optic device150may include an optical modulator130that extends in a first direction. The electro-optic device150may include a first recessed portion122and a second recessed portion124that extend in the first direction and are disposed respectively at both sides of the optical modulator130. The optical modulator130may be a region that transmits optical signals. The optical modulator130and the recessed portions122and124may be united into one body. The optical modulator130may be thicker than the recessed portions122and124. The upper surface of the optical modulator130may be higher than the upper surfaces of the recessed portions122and124. The upper surfaces of the recessed portions122and124may be flat. The electro-optic device150may include silicon.

The optical modulator130may include a first conductivity type semiconductor layer134disposed on the substrate100. The optical modulator130may include a second conductivity type semiconductor layer136disposed on the first conductivity type semiconductor layer134. The optical modulator130may include a junction layer138disposed between the first conductivity type semiconductor layer134and the second conductivity type semiconductor layer136.

The first conductivity type semiconductor layer134and the second conductivity type semiconductor layer136may include regions doped with different dopants. For example, the first conductivity type semiconductor layer134may include a region doped with P-type dopants, and the second conductivity type semiconductor layer136may include a region doped with N-type dopants. Unlike this, the first conductivity type semiconductor layer134may include a region doped with N-type dopants, and the second conductivity type semiconductor layer136may include a region doped with P-type dopants. The junction layer138may be a depletion region. The density of carriers in the depletion region may be lower than the density of carriers in the first conductivity type semiconductor layer134and the second conductivity type semiconductor layer136. The first conductivity type semiconductor layer134, the second conductivity type semiconductor layer136, and the junction layer138may constitute a diode. The doping concentration of the region doped with P-type dopants may be different from the doping concentration of the region doped with N-type dopants. Preferably, the doping concentration of the region doped with P-type dopants may be about 2 to 4 times higher than the doping concentration of the region doped with N-type dopants.

A reverse bias voltage may be applied to the first conductivity type semiconductor layer134and the second conductivity type semiconductor layer136. For example, if the first conductivity type semiconductor layer134includes a region doped with P-type dopants and the second conductivity type semiconductor layer136includes a region doped with N-type dopants, a voltage applied to the first conductivity type semiconductor layer134may be lower than a voltage applied to the second conductivity type semiconductor layer136. Unlike this, if the first conductivity type semiconductor layer134includes a region doped with N-type dopants and the second conductivity type semiconductor layer136includes a region doped with P-type dopants, a voltage applied to the first conductivity type semiconductor layer134may be higher than a voltage applied to the second conductivity type semiconductor layer136.

The thickness of the junction layer138may be controlled according to the level of the reverse bias voltage applied to the first conductivity type semiconductor layer134and the second conductivity type semiconductor layer136. The carrier density of the optical modulator130may be controlled according to the level of the reverse bias voltage. For example, as the level of the reverse vias voltage increases, the thickness of the junction layer138increases, thus reducing the carrier density of the optical modulator130.

The junction layer138may include a first surface contacting the first conductivity type semiconductor layer134and a second surface contacting the second conductivity type semiconductor layer136. The first surface of the junction layer138may be lower than the upper surfaces of the recessed portions122and124. The second surface of the junction layer138may be higher than the upper surfaces of the recessed portions122and124. The recessed portions122and124may include a region that is doped with the same dopants as the first conductivity type semiconductor layer134.

A cladding layer110may be disposed between the substrate100and the optical modulator130. The cladding layer110may be disposed between the substrate100and the recessed portions122and124. The cladding layer110may be disposed over the substrate100. The cladding layer110may include a material that has a different refractive index than the optical modulator130. For example, the cladding layer110may include an oxide layer. The cladding layer110may include a buried oxide layer of a SOI substrate. Unlike this, the cladding layer110may be formed by implanting oxygen ions at a predetermined depth of a bulk semiconductor substrate by ion implantation. The oxygen ion implantation may be selectively performed at a portion for an optical waveguide. This means implanting oxygen ions selectively at a portion for an optical waveguide in the substrate. If the substrate100includes silicon, the cladding layer110may include silicon oxide. The vertical concentration of the silicon oxide may have a Gaussian distribution.

The electro-optic device150may include a light-receiving surface131receiving a first optical signal10. The first optical signal10may be received from a first optical waveguide160. The first optical signal10may travel in the first direction. The electro-optic device150may include a light-outputting surface132outputting a second optical signal20. The second optical signal20may be outputted to a second optical waveguide170. The second optical signal20may travel in the first direction.

The optical modulator130may absorb the first optical signal10received through the light-receiving surface131. The first optical signal10may have a higher intensity than the second optical signal20. The optical absorption factor of the optical modulator130may depend on the carrier density of the optical modulator130. The carrier density of the optical modulator130may depend on the thickness of the junction layer138. The thickness of the junction layer138may depend on the level of the reverse bias voltage applied to the first conductivity type semiconductor layer134and the second conductivity type semiconductor layer136.

The refractive index of the optical modulator130may depend on the carrier density of the optical modulator130. The carrier density of the optical modulator130may depend on the thickness of the junction layer138. The thickness of the junction layer138may depend on the level of the reverse bias voltage applied to the first conductivity type semiconductor layer134and the second conductivity type semiconductor layer136. For example, as the level of the reverse bias voltage increases, the thickness of the junction layer138may increase. If the thickness of the junction layer138increases, the carrier density of the optical modulator130may decrease. If the carrier density of the optical modulator130decreases, the refractive index of the optical modulator130may decrease. The second optical signal20and the first optical signal10entering the optical modulator130may have a phase difference due to a variation in the refractive index of the optical modulator130.

Specifically, the phase difference between the first optical signal10and the second optical signal20may be controlled by a variation in an effective refractive index of the optical modulator130. The variation in the effective refractive index may be defined as the product of the variation in the refractive index and a confinement factor. The confinement factor may be defined as the ratio of the intensity of an optical signal passing a portion with a variable refractive index in the optical modulator130to the total intensity of an optical signal passing the optical modulator130. The variation in the refractive index may be represented as the variation in the refractive index of the optical modulator130according to the level of the reverse bias voltage applied to the first conductivity type semiconductor layer134and the second conductivity type semiconductor layer136.

Accordingly, as the variation in the refractive index of the optical modulator130increases and the intensity of an optical signal passing the junction layer138increases, the variation in the effective refractive index of the optical modulator130may increase. As the variation in the effective refractive index of the optical modulator130increases, the phase modulation speed of the optical signal may increase.

A semiconductor device350may be provided on the substrate100of the switching region104. The semiconductor device350may include a gate insulating layer352on the substrate100. The semiconductor device350may include a gate electrode354on the gate insulating layer352. The gate insulating layer352may include at least one of a silicon oxynitride layer, a silicon nitride layer, a silicon oxide layer and a metal oxide layer. The gate electrode354may include at least one of a doped polysilicon layer, a metal layer and a metal oxide layer.

An optical device may be disposed on the substrate100. The optical device may include an arrayed waveguide grating (AWG) device or grating couplers160and170. The first grating coupler160may be connected to the light-receiving surface131of the electro-optic device150. The first grating coupler160includes an input transmission region and an input diffraction grating. The input diffraction grating is disposed on the surface of the input transmission region. The input transmission region may be formed of a semiconductor. A first optical fiber180may be disposed on the first grating coupler160. An optical signal irradiated from the first optical fiber180is provided through the input diffraction grating to the input transmission region. At this point, due to the input diffraction grating, an optical signal in the input transmission region is inputted to the optical device150in a direction parallel to the upper surface of the substrate100.

The second grating coupler170may be connected to the light-outputting surface132of the electro-optic device150. The second grating coupler170may include an output transmission region and an output diffraction grating. The output diffraction grating is disposed on the upper surface of the output transmission region. The output transmission region may be formed of a semiconductor. A second optical fiber190may be disposed on the second grating coupler170. An optical signal phase-shifted by passing the electro-optic device150is supplied through the output transmission region and the output diffraction grating to the second optical fiber190. The optical signal supplied to the second optical fiber190may be supplied to another semiconductor chip and/or another electronic medium.

Hereinafter, a description will be given of an electro-optic device according to a modification of an embodiment of the present invention.FIG. 2Bis a sectional view of an electro-optic device according to a modification of an embodiment of the present invention. An electro-optic region102ofFIG. 2Bis a sectional view taken along a line I-I′ ofFIG. 1, and a switching region104ofFIG. 2Bmay be a peripheral circuit region spaced apart from the electro-optic region102. A description of an overlap withFIG. 2Awill be omitted for conciseness.

Referring toFIG. 2B, a first conductivity type semiconductor layer134may be thinner than recessed portions122and124. A junction layer138may be lower than the upper surfaces of the recessed portions122and124.

The recessed portions122and124may include a region that is doped with the same dopants as the first conductivity type semiconductor layer134and the second conductivity type semiconductor layer136. The junction layer138may extend from the optical modulator130to the recessed portions122and124.

Hereinafter, a description will be given of an electro-optic device according to another modification of an embodiment of the present invention.FIG. 2Cis a sectional view of an electro-optic device according to another modification of an embodiment of the present invention. An electro-optic region102ofFIG. 2Cis a sectional view taken along a line I-I′ ofFIG. 1, and a switching region104ofFIG. 2Cmay be a peripheral circuit region spaced apart from the electro-optic region102. A description of an overlap withFIG. 2Awill be omitted for conciseness.

Referring toFIG. 2C, a first conductivity type semiconductor layer134may be thicker than recessed portions122and124. A junction layer138may be higher than the upper surfaces of the recessed portions122and124. The recessed portions122and124may include a region that is doped with the same dopants as the first conductivity type semiconductor layer134.

Hereinafter, a description will be given of an electro-optic device according to another embodiment of the present invention.FIG. 4is a sectional view of an electro-optic device according to another embodiment of the present invention. An electro-optic region202ofFIG. 4is a sectional view taken along a line I-I′ ofFIG. 1, and a switching region204ofFIG. 4may be a peripheral circuit region spaced apart from the electro-optic region202.

Referring toFIGS. 1,3and4, a substrate200may include an electro-optic region202and a switching region204. An electro-optic device250may be disposed on the substrate200of the electro-optic region202. The electro-optic device250may include an optical modulator230and recessed portions222and224. The recessed portions222and224may extend from the optical modulator230and may be thinner than the optical modulator230. The optical modulator230may extend in a first direction. The optical modulator230may be a region that transmits optical signals. The optical modulator230and the recessed portions222and224may be united into one body.

The optical modulator230may include a first conductivity type semiconductor layer234and a second conductivity type semiconductor layer236that are disposed on the substrate200. The optical modulator230may include a junction layer238disposed between the first conductivity type semiconductor layer234and the second conductivity type semiconductor layer236.

The interfaces between the first conductivity type semiconductor layer234, the second conductivity type semiconductor layer236and the junction layer238may intersect the upper surface of the substrate200. The interfaces may be perpendicular to the upper surface of the substrate200. A reverse bias voltage may be applied to the first conductivity type semiconductor layer234and the second conductivity type semiconductor layer236.

The doping concentration of the first conductivity type semiconductor layer234may be about 2 to 4 times higher than the doping concentration of the second conductivity type semiconductor layer236. The first conductivity type semiconductor layer234may include a region doped with P-type dopants, and the second conductivity type semiconductor layer236may include a region doped with N-type dopants. The doping concentration of the region doped with P-type dopants is about 2 to 4 times higher than the doping concentration of the region doped with N-type dopants.

The optical modulator230may include a light-receiving surface131receiving a first optical signal10and a light-outputting surface132outputting a second optical signal20. The phase difference between the first optical signal10and the second optical signal20may depend on the level of the reverse bias voltage. The optical absorption factor of the junction layer238with respect to the first optical signal10may depend on the level of the reverse bias voltage.

A cladding layer210may be disposed between the substrate200and the optical modulator230. The cladding layer210may be disposed between the substrate200and the recessed portions222and224.

The optical modulator230may include a first sidewall223and a second sidewall225that extend respectively from the upper surfaces of the recessed portions222and224. Specifically, the first sidewall223may be the sidewall of the first conductivity type semiconductor layer234that extend from the upper surface of the first recessed portion222. The second sidewall225may be the sidewall of the second conductivity type semiconductor layer236that extend from the upper surface of the second recessed portion224. The junction layer238may be disposed between the first sidewall223and the second sidewall225.

The first recessed portion222may include a region that is doped with the same dopants as the first conductivity type semiconductor layer234. The second recessed portion224may include a region that is doped with the same dopants as the second conductivity type semiconductor layer236.

A semiconductor device350including a gate insulating layer352and a gate electrode354may be provided on the substrate200of the switching region204. The gate electrode354may include a doped polysilicon.

An optical device may be disposed on the substrate200. The optical device may include an arrayed waveguide grating (AWG) device or grating couplers160and170. The first grating coupler160may be connected to the light-receiving surface131of the electro-optic device250. The first grating coupler160includes an input transmission region and an input diffraction grating. The input diffraction grating is disposed on the surface of the input transmission region. The input transmission region may be formed of a semiconductor. A first optical fiber180may be disposed on the first grating coupler160. An optical signal irradiated from the first optical fiber180is provided through the input diffraction grating to the input transmission region. At this point, due to the input diffraction grating, an optical signal in the input transmission region is inputted to the optical device150in a direction parallel to the upper surface of the substrate200.

The second grating coupler170may be connected to the light-outputting surface132of the electro-optic device250. The second grating coupler170may include an output transmission region and an output diffraction grating. The output diffraction grating is disposed on the upper surface of the output transmission region. The output transmission region may be formed of a semiconductor. A second optical fiber190may be disposed on the second grating coupler170. An optical signal phase-shifted by passing the electro-optic device250is supplied through the output transmission region and the output diffraction grating to the second optical fiber190. The optical signal supplied to the second optical fiber190may be supplied to another semiconductor chip and/or another electronic medium.

Hereinafter, a description will be given of a variation in the effective refractive index of the optical modulator according to embodiments of the present invention.

FIG. 6is a graph illustrating a variation in the effective refractive index of the optical modulator according to embodiments of the present invention.

Referring toFIG. 6, the graph represents the results of measurement of the variation in the effective refractive index when the reverse bias voltage is applied to the P-type doped region and the N-type doped region. The axis of abscissas represents the doping concentration of the P-type doped region, and the axis of ordinates represents the variation in the effective refractive index.

A curve a) represents the variation in the effective refractive index according to a variation in the doping concentration of the P-type doped region when the doping concentration of the N-type doped region is fixed at 1016cm−3. A curve b) represents the variation in the effective refractive index according to a variation in the doping concentration of the P-type doped region when the doping concentration of the N-type doped region is fixed at 1017cm−3. A curve c) represents the variation in the effective refractive index according to a variation in the doping concentration of the P-type doped region when the doping concentration of the N-type doped region is fixed at 1018cm−3. A curve d) represents the variation in the effective refractive index according to a variation in the doping concentration of the P-type doped region when the doping concentration of the N-type doped region is fixed at 1019cm−3. A curve e) represents the variation in the effective refractive index according to a variation in the doping concentration of the P-type doped region when the doping concentration of the N-type doped region is fixed at 1020cm−3.

As the doping concentrations of the P-type doped region and the N-type doped region increase, the variation in the effective refractive index increases. In particular, if the doping concentration of the P-type doped region is about 2 to 4 times higher than the doping concentration of the N-type doped region, the variation in the effective refractive index may be maximized.

According to the embodiments of the present invention, the first conductivity type semiconductor layer134and the second conductivity type semiconductor layer136are doped with different dopants (i.e., N-type dopants and P-type dopants), and the doping concentration of the P-type doped region is about 2 to 4 times higher than the doping concentration of the N-type doped region, thus making it possible to provide the electro-optic device optimized for high efficiency and low power consumption.

Hereinafter, a description will be given of an application example of an electro-optic device according to embodiments of the present invention.

FIG. 5is a plan view illustrating an application example of an electro-optic device according to embodiments of the present invention.

Referring toFIG. 5, A Mach-Zehnder interferometer may include an input Y-branch410, a first electro-optic device430, an output Y-branch420, and a second electro-optic device440. One of the first and second electro-optic devices430and440may include the electro-optic device according to the embodiments of the present invention. Unlike this, both of the electro-optic devices430and440may include the electro-optic device according to the embodiments of the present invention.

The first electro-optic device430and the second electro-optic device440may be connected between two arms of the input Y-branch410and two arms of the output Y-branch420. An optical signal may be inputted to the input Y-branch410. The optical signal inputted to the input Y-branch410may be divided into first and second optical signals at the branch point of the input Y-branch410. The first optical signal and the second optical signal may be inputted respectively to the first electro-optic device430and the second electro-optic device440. The first and second optical signals inputted to the first and second electro-optic devices430and440may be phase-shifted by passing the first and second electro-optic devices430and440. The optical signals passing the first and second electro-optic devices430and440may be combined at the output Y-branch420. When combined at the output Y-branch, the optical signals may destructively or constructively interfere with each other. The occurrence of the destructive interference or the constructive interference may depend on the phase variation of the optical signals passing the electro-optic devices430and440. The phase variation of the optical signals may depend on the level of a reverse bias voltage applied to the electro-optic devices430and440.

As described above, the present invention can provide electro-optic devices that are optimized for high-speed optical modulation, low power consumption and high integration by a first conductivity type semiconductor layer and a second conductivity type semiconductor layer that have a specific doping concentration difference therebetween and have a reverse bias voltage applied thereto.