JP2001154161A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device capable of impressing a bias voltage to an optical semiconductor element, and capable of efficiently releasing a photocarrier generated in a semiconductor layer to the outside part of the optical semiconductor element. SOLUTION: An optical module 100 is provided with on EA modulator 102 and a short circuit 104. When an optical signal modulated by a high speed signal is made incident on an EA modulator 102 to which a bias voltage is impressed, optical currents according to the strength of the optical signal are generated in the absorbing layer of the EA modulator 105. The high frequency components of the optical currents are allowed to flow from an upper electrode 102a of the EA modulator 102 to a short circuit 104. In the short circuit 103, a capacitor C1 turns the upper electrode 102a into a grounded state against the high frequency power of a frequency f1, and a capacitor C2 turns the upper electrode 102a into a grounded state against the high frequency power of a frequency f2, and a capacitor C3 turns the upper electrode 102a into a grounded state against the high frequency power of a frequency f3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor device having an optical semiconductor element.

[0002]

2. Description of the Related Art Conventionally, as a semiconductor device having an optical semiconductor element, there is an optical module 400 disclosed in the following document. "Tatsumi Well, Hiroaki Inoue," Semiconductor Optical Control Devices and Packaging, "Journal of Japan Institute of Circuit Packaging Vol. 10 NO. 5 (19
95) pp. 306-309 "First, referring to FIG. 14 and FIG.
0 will be described. FIG. 14 is the same as FIG.
FIG. 15 corresponds to FIG. 6 of the above document.

[0003] An optical module 400 is an electroabsorption type optical modulator (Electro-Absorp) as an optical semiconductor element.
"EA modulator";
That. ) 402 is provided. The EA modulator 402
An optical semiconductor device having an optical waveguide having a PIN structure and performing intensity modulation on light propagating through the optical waveguide. In the EA modulator 402, the amount of light absorption in the absorption layer can be changed by applying a reverse bias voltage to the optical waveguide having the PIN structure and applying an electric field to the absorption layer (I layer).

Generally, the modulation band of an EA optical modulator is limited by its element capacity. Therefore, in the above document,
By reducing the element length of the modulator area of the EA modulator 402 to 100 μm or less to reduce the capacity of the EA modulator 402, the modulation band of the EA modulator 402 is broadened to about 40 GHz. In the above document, a waveguide integrated electro-absorption optical modulator in which an optical waveguide is integrally formed in an optical modulator region is applied to the EA modulator 402. This is for the following reasons.

In the optical module 400, the high-frequency board 408 on which the microstrip line 404 and the terminating resistor 406 are formed needs to have a width of at least 1 mm. Therefore, the width W of the carrier 410 is limited by the width of the high-frequency substrate 408. If the width W does not match the element length of the EA modulator 402, the aspherical lens 4
14, the light condensed on both end faces of the EA modulator 402 impinges on the carrier 410.
There is a possibility that problems such as insufficient light coupling (light collection) at the two end faces or unnecessary scattering of light caused by the carrier 410 may occur. Therefore, in the optical module 400 of the above document, by providing a waveguide region for guiding light to the modulator region, the element length of the entire EA modulator 402 is increased while the length of the modulator region is kept short, and the EA modulator 402 is extended. The element length and the width W of the modulator 402 are matched.

The optical module 400 has the following mounting structure for high-frequency signals. The high-frequency electric signal input from the high-frequency connector 418 passes through the microstrip line 404 and is terminated near the EA modulator 402 chip via the terminating resistor 406. That is, the terminating resistor 40 is connected to the microstrip line 404.
6 and grounded via a terminating resistor 406. The connection of the termination resistor 406 of the microstrip line 404 is connected to the EA modulator 402 by a bonding wire 422.

[0007]

However, in the conventional optical module 400, the microstrip line 404 is used as the high-frequency transmission line, and a 50Ω resistor is connected in parallel to the microstrip line 404 as the terminating resistor 406. Therefore, the high frequency characteristics are not sufficient. Therefore, the generated photocurrent can be efficiently EA
It cannot flow outside the modulator 402. FIG. 15 shows the high-frequency characteristics of the optical module 400.
When the modulation region length l of the modulator 102 is 100 μm,
The degree of modulation at 26 GHz or higher is -3 dB or higher. That is, FIG.
At 0, the photocurrent having a frequency of 26 GHz or more is EA
It does not flow out of the modulator 402.

Here, consider the case where the above-mentioned conventional optical module 400 is used in the following situation. When an optical signal modulated by a high-speed digital signal enters the EA modulator 402, a photocurrent corresponding to the optical signal is generated in the EA modulator 402 due to its absorption characteristics. Such photocurrent is
The current is supplied to the outside through a connection circuit electrically connected to the EA modulator 402. Since the photocurrent is a high-frequency signal, the high-frequency characteristics of the connection circuit are important. When such a photocurrent does not flow well from the EA modulator 402, photo carriers accumulate in the EA modulator 402, and there is a high possibility that the absorption characteristics of the EA modulator 402 deteriorate.

As described above, a semiconductor device provided with an optical semiconductor element generally requires a circuit for rapidly releasing photocarriers generated in the optical semiconductor element to the outside of the optical semiconductor element at high frequency. Furthermore, if a photocurrent can be quickly passed outside the optical semiconductor element in a wide band, the semiconductor device can be used regardless of the frequency.

As a configuration for allowing photocarriers generated in the optical semiconductor element to escape to the outside of the optical semiconductor element, a configuration in which the output electrode of the optical semiconductor element is short-circuited to the ground by a bonding wire or the like can be considered. However, in such a configuration, although a very good short-circuit state can be created in a wide band, it is difficult to apply a bias voltage to the optical semiconductor element. The present invention has been made in view of the above and other problems of a conventional semiconductor device.

[0011]

In order to solve the above-mentioned problems, the present invention relates to an optical semiconductor having a semiconductor layer in which photocarriers are generated by input of light and an output electrode for outputting the photocarriers as high-frequency power. The following configuration is employed in a semiconductor device having an element and receiving a high-frequency optical signal of a predetermined frequency as light.

The first aspect of the present invention employs a configuration including a short circuit that is connected to the output electrode and sets the output electrode to a ground state with respect to high frequency power of a predetermined frequency output from the output electrode. Here, the grounding state refers to a state in which the high-frequency power output from the output electrode flows to the ground at a high frequency, and the output electrode does not need to be DC-grounded.

According to the invention described in this section, photocarriers generated in the semiconductor layer can be quickly released to the outside of the optical semiconductor element by the short circuit. Therefore, according to the invention described in this section, it is possible to prevent functional deterioration of the optical semiconductor element that operates at high speed. In the invention described in this section, it is preferable to apply, to the short circuit, a circuit that does not ground the output electrode with respect to other predetermined frequency power and DC power. This is because generally, in an optical semiconductor device, it is necessary to apply a bias electric field to a semiconductor layer.

Here, as in the second aspect of the present invention,
The short circuit can employ a configuration including one or more capacitors (capacitors) in which one electrode is grounded and the other electrode is connected to the output electrode. If the output electrode is grounded at a high frequency using a capacitor as in the invention described in this section, a short circuit can be formed relatively easily.

In the invention according to the present application, each capacitor can be connected to the output electrode independently of each other. In such a configuration, since the configuration of the connection line between the capacitor and the output electrode can be set independently of each other, the self-resonant frequency of the circuit including each capacitor can be set independently of each other.

In the invention according to the present application, each capacitor can be connected to the output electrode in a ladder shape. That is, as in the third aspect of the present invention,
One of the first to n-th capacitors is grounded, the other electrode of the first capacitor is connected to the output electrode, and the other electrode of the (k + 1) -th capacitor is connected to the other electrode of the k-th capacitor. A configuration connected to the electrode can be adopted. Note that n is an integer of 2 or more, and k is an arbitrary integer of 1 or more and (n-1) or less.

In such a configuration, the arrangement space of the capacitors in the semiconductor device can be reduced as compared with a configuration in which each capacitor is connected to the output electrode independently of each other.
Here, as in the invention described in claim 4, the k-th capacitor can adopt a configuration having a smaller capacitance than the (k + 1) -th capacitor.

According to a fifth aspect of the present invention, the short circuit includes one or more dielectric substrates, and one or two dielectric substrates installed on the surface of the dielectric substrate and connected to the output electrodes.
A configuration including the above-described open stub can be adopted. In the invention described in this section, the impedance of the short circuit can be easily adjusted by adjusting the length of the open stub. In general, a grounded conductor is opposed to the open stub.

Further, as in the invention according to claim 6,
The short circuit includes one or more dielectric substrates, two or more open stubs installed on the surface of the dielectric substrate,
A configuration including one or more microstrip lines that connect the open stub to the output electrode can be adopted. Here, in the invention according to the present application, each open stub can be connected to the output electrode in a ladder shape.

In the invention according to the present application, each open stub can be connected to the output electrode independently of each other.
That is, as in the invention according to claim 7, the short circuit includes one or more dielectric substrates and two or more open stubs which are provided on the surface of the dielectric substrate and are connected to the output electrodes independently of each other. The configuration provided can be adopted.
In such a configuration, the configuration of the open stubs can be set independently of each other, so that the impedance of each open stub can be set independently of each other.

[0021]

Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the following description and the accompanying drawings, components having the same function and configuration are denoted by the same reference numerals, and redundant description is omitted.

(First Embodiment) First, a first embodiment will be described with reference to FIGS. Note that FIG.
3 is an equivalent circuit diagram of the short circuit 104 according to the embodiment. FIG. 2 is a schematic configuration diagram of the carrier 106.
FIG. 2A which is a plan view and FIG. 2 which is a cross-sectional view along AA ′
(B). FIG. 3 is a schematic configuration diagram of the optical module 100 according to the present embodiment, and includes FIG. 3A which is a cross-sectional view in a plane direction and FIG. 3B which is a cross-sectional view in a side direction. FIG. 4 is a Smith chart showing a calculation result regarding the impedance of the short circuit 104.

As shown in FIGS. 3A and 3B, the optical module 100 according to the present embodiment has
This is a semiconductor device including the A modulator 102. The optical module 100 includes a short circuit 1 other than the EA modulator 102.
04, a carrier 106, and a mounting frame 108. In the optical module 100, the EA modulator 102
The short circuit 104 is installed on the metal base 162 of the carrier 106. Further, the carrier 106
Is installed on the base 180 of the mounting frame 108.

As shown in FIG. 1, in the short circuit 104 according to the present embodiment, the upper electrode 102a of the EA modulator 102 can be grounded with respect to the high frequency power having the specific frequency of 3. The short circuit 104 includes three capacitors C1 to C3. Capacitors C1 to C3
Is the capacitance (capacity) when viewed electrically
This is equivalent to a circuit in which a parasitic resistance and a parasitic inductor are connected in series.

Although the optical module 100 has a configuration including three capacitors C1 to C3, the present embodiment is not limited to this configuration. In this embodiment, a configuration including n capacitors having appropriate capacitance, inductance, and impedance may be employed. Here, n is an arbitrary integer of 1 or more. In such a configuration, the upper electrode 102a of the EA modulator 102 can be grounded with respect to the high frequency power of the frequency n by the short circuit.

As shown in FIGS. 2A and 2B, in the short circuit 104, the capacitors C1 to C3 are connected in a ladder shape from the upper electrode 102a of the EA modulator 102. More specifically, the upper electrode of the capacitor C1 is connected to an upper electrode 102a corresponding to an output electrode by a bonding wire L1, the upper electrode of the capacitor C2 is connected to the upper electrode of the capacitor C1 by a bonding wire L2, and the upper electrode of the capacitor C3 is connected. The electrode is connected to the upper electrode of the capacitor C2 by a bonding wire L3. In other words, the upper electrode 102 of the EA modulator 102
The upper electrodes of the capacitors C1 to C3 are sequentially connected in series to a.

In this embodiment, the capacitors C1 to C1
C3 can be connected to the EA modulator 102 independently of each other. That is, in the present embodiment, the upper electrode of the capacitor C1 is connected to the EA modulator 10 by the bonding wire L1.
2 and the upper electrode of the capacitor C2 is connected to the upper electrode 102a by a bonding wire L2.
And the upper electrode of the capacitor C3 can be connected to the upper electrode 102a by a bonding wire L3. This connection method is superior to the connection method according to the optical module 100 in that the characteristics of the short circuit 104 can be designed relatively freely. On the other hand, optical module 1
The above connection method 00 is more advantageous in consideration of the mounting area, optical coupling (lens mounting), and the like.

Further, in the short circuit 104, the lower electrodes of the capacitors C1 to C3 are all connected to the metal base 162. Furthermore, the capacitor C
As for 1 to C3, those having smaller capacitance are arranged in order from the one closer to the EA modulator 102. That is, the capacitor C2 has a smaller capacitance than the capacitor C3, and the capacitor C1 has a smaller capacitance than the capacitor C2.

In this embodiment, the capacitors C1 to C
3 is desirable to make the self-resonant frequency as high as possible. Therefore, it is desirable to use a parallel plate type capacitor using a ferroelectric material having a small parasitic inductance instead of a multilayer type capacitor for the short circuit 104.

The carrier 106 includes a metal base 162 and a micro-strip line (Micro-Strip).
Line: Hereinafter, referred to as “MSL”. ) 164 and a high-frequency substrate 166 formed of a dielectric material.

The MSL 164 is disposed on the surface of the metal base 162 by being formed on the surface of the high-frequency substrate 166 provided on the surface of the metal base 162. The MSL 164 is an electric wiring for connecting the bias circuit 110 outside the optical module 100 to the upper electrode 102a of the EA modulator 102. In the optical module 100, one end of the MSL 164 is connected to the bias circuit 110 by a bonding wire, and the other end is connected to the upper electrode 102a by a bonding wire L1.

On the surface of the metal base 162, a substrate installation area 162a and an element mounting area 162b are formed. The substrate mounting region 162a is a region where the high frequency substrate 166 is mounted, and the element mounting region 162b is a region where the EA modulator 10 is mounted.
2 and the area where the capacitors C1 to C3 of the short circuit 104 are mounted. In the optical module 100, the EA modulator 102, the capacitors C1 to C3, and the high-frequency board 3 can be fixed to the surface of the metal base 162 by soldering or other fixing means.

As shown in FIGS. 3A and 3B, the mounting frame 108 includes a lens 182, a lens holder 184, and an optical fiber 186. The lens 182 is held and fixed by a lens holder 184, and is arranged on an optical axis connecting the optical waveguide of the EA modulator 102 and the core of the optical fiber 186. The distance between the lens 182 and the EA modulator 102 is adjusted such that the focal point of the lens 184 is substantially on the light input / output end face of the EA modulator 102.

In the optical module 100, the lens 18
2 couples the light output from the optical fiber 186 to the optical waveguide of the EA modulator 102 and couples the light output from the optical waveguide of the EA modulator 102 to the optical fiber 186.
Optically coupled. The lens 182 includes the lens 18
It is preferable to apply an aspheric lens in order to prevent the contact between the carrier 2 and the carrier 106.

Further, the mounting frame 108 includes a base 18 on which the carrier 106 and the lens holder 184 are installed.
0 is provided. In the optical module 100, the EA modulator 10 is provided on the base 180 via the carrier 106.
2 and a short circuit 104, and a lens 182 via a lens holder 184.

Further, the mounting frame 108 has an electronic cooling element 188. In the mounting frame 108, a base 180 is installed on the electronic cooling element 188. That is, the base 18 is placed on the electronic cooling element 188.
The EA modulator 102 is installed via the “0” and the carrier 106. In the optical module 100, the electronic cooling element 188 cools the EA modulator 102 via the carrier 106 (metal base 162) and the base 180, and
The modulator 102 performs a constant temperature operation.

Further, the mounting frame 108 includes a connector 190 and a package 192. Connector 1
90 interconnects the MSL 164 and the bias circuit 110 to apply a bias voltage to the EA modulator 102. The package 192 includes the EA modulator 102, the short circuit 104, the carrier 106, the base 180, the lens 182, the lens holder 184, and the optical fiber 186.
And an electronic cooling element 188 are accommodated.

In the optical module 100, the metal base 162 is connected to the package 182,
Package 182 is grounded. With such a configuration,
The lower electrode of the EA modulator 102 and the lower electrodes of the capacitors C1 to C3 correspond to the metal base 162 and the package 182.
And grounded through.

The optical module 100 described above needs to be designed so that the carrier 106 and the optical system such as the lens 182 can perform good optical coupling without interference (without collision) with each other. . Further, the wire length of the bonding wires L1 to L4 in the optical module 100 needs to be adjusted so that the bonding wires L1 to L4 have an inductance as designed.

Next, the operation of the optical module according to this embodiment will be described. The optical signal modulated by the high-speed signal is E
When the light enters the A modulator 102, a photocurrent corresponding to the intensity of the optical signal is generated in the absorption layer of the EA modulator 102.
The low frequency component of the photocurrent flows to the bias circuit 110 through the MSL 164. On the other hand, the high frequency component of the photocurrent flows from the upper electrode 102a of the EA modulator 102 to the short circuit 104. In the short circuit 104,
The high frequency component is input to the capacitor C1 through the bonding wire L1, input to the capacitor C2 through the bonding wires L1 and L2, and input to the capacitor C3 through the bonding wires L1, L2 and L3.

Among the high frequency components, the component of the specific frequency f1 flows to the ground via the capacitor C1, another component of the specific frequency f2 flows to the ground via C2, and the component of another frequency f3 is connected to the capacitor C3. Flows to the ground through. That is, the capacitor C1 has the frequency f1
The upper electrode 102a is grounded to the high frequency power of
The capacitor C2 sets the upper electrode 102a to the ground state with respect to the high frequency power of the frequency f2, and the capacitor C3 sets the frequency f
The upper electrode 102a is grounded for the high frequency power of No. 3. The output electrodes 102 are connected by the capacitors C1 to C3.
The frequencies f1, f2, and f3 at which a is grounded have a certain width.

In general, the impedance Z of a capacitor
Is represented by Z = 1 / (2πfC). Here, f indicates the frequency of the high-frequency power applied to the capacitor, and C indicates the capacitance of the capacitor. Therefore, ideally, in a capacitor, as the frequency f increases and the capacitance C increases, the impedance Z decreases, and the upper electrode and the lower electrode are short-circuited. However, in practice, when the frequency f becomes higher than a certain frequency, the impedance Z becomes higher because of the parasitic inductance of the capacitor itself and an inductance component (such as a bonding wire) connected to the capacitor. Such a certain frequency is the self-resonant frequency.

Therefore, in the optical module 100 according to this embodiment, the upper electrode 1
In order to ground the second circuit 02a, the configuration of the entire circuit including the EA modulator 102 and the short circuit 104 is taken into consideration.
It is necessary to set the capacitance of the capacitors C1 to C3.

FIG. 4 is a Smith chart showing a calculation result of the impedance (S11) of the short circuit 104 viewed from the upper electrode 102a in the optical module 100. The circuit constant used for the calculation is the value illustrated in FIG.
The upper electrode 102a of the optical modulator 102 was set to be in a ground state with respect to the high frequency power of 40 GHz. As can be understood from FIG.
Thus, it can be seen that the impedance of the short circuit 104 decreases and the short circuit 104 is in a short state.

As described above, in the optical module according to the present embodiment, the capacitor is connected in parallel between the upper electrode of the EA modulator and the ground. further,
The upper electrode of the EA modulator according to the present embodiment is connected to a bias circuit via the MSL. Therefore, EA
While applying a bias voltage to the modulator, high-frequency power of a specific frequency generated by the EA modulator can be released to ground via a capacitor. As a result, according to the present embodiment, it is possible to increase the bandwidth of the EA modulator without impairing the light absorption modulation function of the EA modulator due to the application of the bias voltage.

(Second Embodiment) Next, a second embodiment will be described mainly with reference to FIGS. FIG. 8 is an equivalent circuit diagram of the short circuit 204 according to the present embodiment. FIG. 9 is a schematic configuration diagram of the carrier 206 of the optical module 200 according to the present embodiment, and includes FIG. 9A which is a plan view and FIG. 9B which is a cross-sectional view taken along the line BB ′. FIG. 10 is a Smith chart showing a calculation result of the impedance of the short circuit 204.

The optical module 200 according to this embodiment is
The optical module 100 according to the first embodiment is different from the optical module 100 in the configuration of the short circuit and the carrier. In other respects, the optical module 200 has substantially the same configuration as the optical module 100 according to the first embodiment. Hereinafter, the short circuit 20 of the optical module 200 according to the present embodiment will be described.
4 and the carrier 206 will be described in detail.

As shown in FIGS. 9A and 9B, the carrier 206 has a metal base 262 and a high-frequency substrate 266. In the carrier 206, the high-frequency substrate 26
6, a bias wiring 268 and a short circuit 204 are formed. The high-frequency board 266 is installed in the board installation area 262a on the surface of the metal base 262 by, for example, soldering. In the optical module 200, the element mounting area 262b on the surface of the metal base 262
Is provided with an EA modulator 102 by, for example, soldering.

As shown in FIG.
Is the MSL 240 and open stubs 242 and 244
And MSL240 and open stub 242
And 244 are high-frequency substrates 2 corresponding to dielectric substrates.
66. With this configuration, the open stubs 242 and 244 are arranged to face the surface of the metal base 262 via the high-frequency substrate 266.

The MSL 240 includes a first part 240a and a second part 240a.
And a portion 240b. In the MSL 240, the end of the first portion 240a opposite to the second portion 240b is connected to the EA modulator 10 by a bonding wire L5.
2 upper electrodes 102a. In addition, the second
The end of the first part 240a on the part 240b side is connected to the open stub 242. Further, an appropriate position of the first portion 240a is connected to the bias circuit 110 by a bonding wire L6 and a bias wiring 268. The end of the second portion 240b opposite to the first portion 240a is connected to the open stub 244.

In this embodiment, the MSL 240, the open stubs 242 and 244, and the bias wiring 268 can be formed by, for example, a metallized pattern of Au or another metal. In this embodiment,
The MSL 240 includes a first portion 240a and a second portion 240a.
The line width of the first portion 240a and the line width of the second portion 240b may be different from each other.

Further, the optical module 200 has a configuration including two open stubs 242 and 244, but the present embodiment is not limited to this configuration. In this embodiment, a configuration in which n open stubs having appropriate impedance and length are connected to MSL having appropriate impedance and length can be adopted. Here, n is an arbitrary integer of 1 or more. In such a configuration, the upper electrode 102a of the EA modulator 102 can be grounded with respect to the high frequency power of n frequencies by the short circuit.

The optical module 20 configured as described above
At 0, the upper electrode 102a of the EA modulator 102 is connected to the ground via the short circuit 204. Due to the action of the open stubs 242 and 244, the impedance of the short circuit 204 decreases when a predetermined high-frequency power is applied, and the short circuit 204 enters a short state. In general, it is known that an open stub enters a short state when a line length L is L = λ / 4 for a certain frequency (wavelength λ).

The optical module 20 according to the present embodiment
At 0, two open stubs 242 and 244 are connected to a single MSL 240. Therefore, the length of the open stubs 242 and 244 does not become a quarter of the corresponding high frequency power wavelength. That is, in the optical module 200, the lengths of the open stubs 242 and 244 are changed by the first portion 240a and the second portion 24
It is necessary to design in consideration of the impedance and the length of 0b.

FIG. 10 is a Smith chart showing the calculation result of the impedance (S11) of the short circuit 204 according to the present embodiment as viewed from the upper electrode 102a at 20 GHz and 40 GHz. Note that the circuit constants illustrated in the circuit diagram in FIG. 8 were used for the calculation. FIG.
In W, MSL 240, open stub 242
And 244, and L is the length of the MSL 240, open stubs 242 and 244. Also,
In this calculation, the dielectric constant of the high-frequency substrate 266 was set to 9.9, assuming that the high-frequency substrate 266 was made of alumina ceramic. As can be seen from FIG.
It can be seen that the short circuit 204 has low impedance at z and 40 GHz.

Here, the operation and effects of the short circuit 204 according to the present embodiment will be described in comparison with the short circuit 104 according to the first embodiment, with reference to FIGS.

FIG. 5 shows the short circuit 104 shown in FIG.
The capacitance of the capacitor C2 is 0.7 pF
20G when changed in the range of ~ 0.9pF
3 shows a change in impedance of the short circuit 104 with respect to high-frequency power of Hz. FIG. 6 shows the short circuit 1 for the high frequency power of 40 GHz when the capacitance of the capacitor C1 is changed in the range of 0.25 pF to 0.3 pF in the short circuit 104 shown in FIG.
4 shows a change in impedance of the circuit. Here, it is assumed that the short circuit 104 releases high-frequency power of 40 GHz to the ground by the capacitor C1 and releases high-frequency power of 20 GHz to the ground by the capacitor C2.

As shown in FIGS. 5 and 6, in the short circuit 104 according to the first embodiment, the capacitor C1
Alternatively, it can be seen that the impedance greatly changes in response to a slight change in the capacitance of C2, and the short circuit 104 comes out of the short state. In an actual capacitor, the tolerance of the capacitance is 0.2 pF to lp
With a capacitance of about F, minimum ± 0.1
There is about pF. Therefore, in the short circuit 104 according to the first embodiment, the capacitors C1 to C3
May not be able to obtain sufficient characteristics due to the variation in the capacitance.

FIG. 7 shows a change in the impedance of the short circuit 104 with respect to a high frequency power of 40 GHz when the length of the bonding wire L1 is changed in the short circuit 104 shown in FIG. FIG.
As shown in FIG. 7, it can be seen that the impedance of the short circuit 104 greatly changes even when the length of the bonding wire L1 changes only by about 0.1 μm. In general, an inductance of about 0.1 nH is converted into 0.1 mm in terms of a bonding wire length.
Is equivalent to Therefore, in the short circuit 104 according to the first embodiment, in order to obtain good characteristics, when the EA modulator 102 and the capacitors C1, C2, and C3 are mounted,
The distance must be adjusted exactly.

On the other hand, the short circuit 20 according to the present embodiment
4, via open stubs 242 and 244,
The upper electrode 102a of the EA modulator 102 is connected to the ground. In general, a stub can be easily adjusted in length, so that it is easier to realize a circuit constant as designed than a capacitor or a bonding wire. Therefore, the short circuit 204 according to the present embodiment is easier to manufacture than the short circuit 104 according to the first embodiment.

As described above, in the optical module according to the present embodiment, the open stub is connected to the upper electrode of the EA modulator via the bonding wire and the MSL. A bias circuit is connected to the upper electrode of the EA modulator via the MSL and a wire. Therefore, in the optical module according to the present embodiment, while applying a bias voltage from the bias circuit to the EA modulator,
High frequency power of a specific frequency generated by the A modulator can be released to the ground via the open stub. As a result, according to the present embodiment, it is possible to increase the bandwidth of the EA modulator without impairing the light absorption modulation function of the EA modulator due to the application of the bias voltage.

Further, in this embodiment, an open stub having a simple structure and having a continuously variable length is used for the short circuit. Therefore, in the optical module according to the present embodiment, the ground state of the EA modulator upper electrode can be created more accurately than in the optical module according to the first embodiment. As a result, according to the present embodiment, the yield of the optical module can be improved.

(Third Embodiment) Next, an optical module 300 according to a third embodiment will be described with reference to FIGS.
Will be described. FIG. 11 is an equivalent circuit diagram of the short circuit 304 according to the present embodiment. FIG. 12 is a schematic configuration diagram of the carrier 306 of the optical module 300 according to the present embodiment, which is a plan view of FIG.
FIG. 12B is a sectional view taken along the line C ′. FIG.
6 is a Smith chart showing a calculation result of an impedance of a short circuit 304.

The optical module 300 according to the present embodiment
The optical module 100 according to the first embodiment is different from the optical module 100 in the configuration of the short circuit and the carrier. In other respects, the optical module 300 has substantially the same configuration as the optical module 100 according to the first embodiment. Hereinafter, the short circuit 30 of the optical module 300 according to the present embodiment will be described.
4 and the carrier 306 will be described in detail.

As shown in FIGS. 12A and 12B, the carrier 306 comprises a metal base 362 and a first high-frequency substrate 36.
6a and a second high-frequency board 366b. In the carrier 306, a bias wiring 368 and an open stub 342 are formed on the first high-frequency substrate 366a. In the present embodiment, the open stubs 342 and 344 and the bias wiring 368 can be formed by a metallized pattern such as gold.

The first high-frequency board 366a is installed in the first board installation area 362a on the surface of the metal base 362 by, for example, soldering. The second high-frequency substrate 36
An open stub 344 is formed on 6b.
The second high-frequency board 366b is installed in the second board installation area 362c on the surface of the metal base 362 by, for example, soldering. Further, in the optical module 300,
In the element mounting area 362b on the surface of the metal base 362,
The EA modulator 102 is installed by, for example, soldering.

As shown in FIG. 11, the short circuit 304
Has open stubs 342 and 344.
The open stub 342 is arranged to face the surface of the metal base 362 via the first high-frequency board 366a, and the open stub 344 is arranged to face the surface of the metal base 362 via the second high-frequency board 366b.

In the short circuit 304 according to the present embodiment, the lengths of the open stubs 342 and 344 are respectively set so as to be ４ times the wavelength of the high-frequency power of a desired frequency (wavelength λ). With this configuration, in the short circuit 304, the upper electrode 10 of the EA modulator 102 is supplied with the high frequency power having the desired frequency.
2a can be grounded.

In the short circuit 304, the open stub 342 and the open stub 344 are connected to the EA modulator 1
02 are independently connected to the upper electrode 102a.
More specifically, one end of the open stub 342 is connected to the upper electrode 1 of the EA modulator 102 by a bonding wire L7.
02a, and one end of the open stub 344 is connected to the upper electrode 102a by a bonding wire L8.

In the optical module 300, a bias wire 368 is connected to an appropriate position of the open stub 342 by a bonding wire L9. With this configuration, it is possible to apply a bias voltage from the bias circuit 110 to the EA modulator 102.

Although the optical module 300 has a configuration including two open stubs 342 and 344, the present embodiment is not limited to this configuration. In this embodiment, a configuration including n open stubs having appropriate impedance and length can be adopted.
Here, n is an arbitrary integer of 1 or more. In such a configuration, the upper electrode 102a of the EA modulator 102 can be grounded with respect to the high frequency power of n frequencies by the short circuit.

The optical module 30 configured as described above
At 0, the upper electrode 102a of the EA modulator 102 is connected to the ground via the short circuit 304. Due to the action of the open stubs 342 and 344, the impedance of the short circuit 304 decreases when a predetermined high-frequency power is applied, and the short circuit 304 enters a short circuit state.

More specifically, in the short circuit 304,
When the high-frequency power generated by light absorption of the EA modulator 102 has a desired specific frequency f1, one of the open stubs 342
Is in a short-circuit state, and the impedance of the other open stub 344 increases. On the other hand, the EA modulator 102
When the high-frequency power generated by the light absorption at frequency f2 is at frequency f2, one open stub 342 is in a short-circuit state, and the other open stub 344 has an increased impedance.

In the short circuit 304 according to the present embodiment, two open stubs 342 and 344 are connected in parallel between the upper electrode 102a and the ground.
Therefore, if either of the open stubs 342 or 344 is in a short state, the entire short circuit 304 is in a short state.

FIG. 13 is a Smith chart showing the calculation result of the impedance (S11) of the short circuit 304 according to the present embodiment viewed from the upper electrode 102a of the EA modulator 102 at 20 GHz and 40 GHz. Note that the circuit constants illustrated in the circuit diagram in FIG. 11 were used for the calculation. In FIG. 11, W is the line width of the open stubs 342 and 344, and L is the length of the open stubs 342 and 344. In the calculation, the first high-frequency substrate 366a and the second high-frequency substrate 3
The first high-frequency board 366a and the second high-frequency board 3
The dielectric constant of 66b was 9.9.

As can be seen from FIG.
It can be seen that the short circuit 304 has a low impedance at 0 GHz. Note that FIG. 13 shows the result shifted from the perfect short point so that the impedance value can be easily understood. However, if the length of the open stub is optimized, the two frequencies can be completely short. is there.

As described above, in the optical module according to the present embodiment, the open stub is connected to the upper electrode of the EA modulator via the bonding wire. A bias circuit is connected to the upper electrode of the EA modulator via a bonding wire. Therefore, while applying a bias voltage from the bias circuit to the EA modulator, high-frequency power of a specific frequency generated by the EA modulator can be released to the ground via the open stub. As a result, according to the present embodiment, it is possible to increase the bandwidth of the EA modulator without impairing the light absorption modulation function of the EA modulator due to the application of the bias voltage.

Further, in this embodiment, an open stub whose configuration is simple and whose length can be continuously changed is used for the short circuit. Therefore, in the optical module according to the present embodiment, the ground state of the EA modulator upper electrode can be created more accurately than in the optical module according to the first embodiment. As a result, according to the present embodiment, the yield of the optical module can be improved.

Further, in the present embodiment, it is possible to independently optimize the characteristics for each frequency with each open stub. Therefore, according to the present embodiment, it is possible to obtain better short circuit characteristics as compared with the second embodiment.

Although the preferred embodiment according to the present invention has been described above, the present invention is not limited to this configuration. A person skilled in the art can envisage various modified examples and modified examples within the scope of the technical idea described in the claims, and these modified examples and modified examples are also included in the technical scope of the present invention. It is understood to be included.

For example, in the above embodiment, a semiconductor device to which an EA modulator is applied as an optical semiconductor element has been described as an example, but the present invention is not limited to such a configuration. The present invention can be applied to other various optical semiconductor elements, for example, an optical semiconductor element using a saturable absorber as a semiconductor layer, or a semiconductor device using a photodiode or the like.

In the above embodiment, a micro-strip line (micro-str) is used as an electric line.
Although a semiconductor device to which an ip line is applied has been described as an example, the present invention is not limited to such a configuration. The present invention can also be applied to a semiconductor device to which various other electric lines, for example, a balanced strip line, a dielectric support strip line, a coplanar line, or a coaxial line are applied. .

Further, in the above embodiment, a semiconductor device to which a short circuit using a capacitor or an open stub is applied has been described as an example, but the present invention is not limited to such a configuration. The present invention can be applied to a semiconductor device to which other various short circuits, for example, a short circuit using a short stub are applied.

Furthermore, in the above embodiment, specific examples of the circuit constant of the semiconductor device have been described, but the present invention is not limited to such a configuration. The present invention can be applied to semiconductor devices having other various circuit constants.
That is, the circuit constants shown in the above embodiment are merely examples of circuit constants applicable to the semiconductor device according to the present invention, and the present invention is applied to a semiconductor device having a different circuit constant, and the same as in the above embodiment. The effect of can be obtained.

[0085]

The semiconductor device according to the present invention has a short circuit for short-circuiting high-frequency power generated by an optical semiconductor element in high frequency. Therefore, according to the present embodiment,
It is possible to provide a mounting structure capable of applying a bias voltage to the optical semiconductor element and efficiently releasing photocarriers generated in the semiconductor layer to the outside of the optical semiconductor element.

[Brief description of the drawings]

FIG. 1 is an equivalent circuit diagram of a short circuit according to a first embodiment.

FIG. 2 is a schematic configuration diagram of a carrier applicable to the optical module according to the first embodiment.

FIG. 3 is a schematic configuration diagram of the optical module according to the first embodiment.

FIG. 4 is a Smith chart showing calculation results of impedance of the short circuit shown in FIG. 1;

FIG. 5 is a Smith chart showing another calculation result of the impedance of the short circuit shown in FIG. 1;

FIG. 6 is another Smith chart showing another calculation result of the impedance of the short circuit shown in FIG. 1;

7 is another Smith chart showing another calculation result of the impedance of the short circuit shown in FIG. 1;

FIG. 8 is an equivalent circuit diagram of a short circuit according to a second embodiment.

FIG. 9 is a schematic configuration diagram of a carrier applicable to the optical module according to the second embodiment.

10 is another Smith chart showing another calculation result of the impedance of the short circuit shown in FIG. 1;

FIG. 11 is an equivalent circuit diagram of a short circuit according to a third embodiment.

FIG. 12 is a schematic configuration diagram of a carrier applicable to the optical module according to the third embodiment.

13 is another Smith chart showing another calculation result of the impedance of the short circuit shown in FIG. 1. FIG.

FIG. 14 is a schematic configuration diagram of a conventional optical module.

FIG. 15 is a diagram illustrating characteristics of a conventional optical module.

[Description of Signs] 100 Optical module 102 EA modulator 102a Upper electrode 104 Short circuit 164 MSL 162 Metal base 242, 244, 342, 344 Open stub C1, C2, C3 Capacitor

Claims (7)

[Claims] An optical semiconductor device having a semiconductor layer in which photocarriers are generated by input of light and an output electrode for outputting the photocarriers as high-frequency power, wherein a high-frequency optical signal of a predetermined frequency is input as the light. A semiconductor device, comprising: a short circuit connected to the output electrode and for setting the output electrode to a ground state with respect to high-frequency power of the frequency output from the output electrode. 2. The short circuit according to claim 1, wherein one electrode is grounded and the other electrode is connected to the output electrode.
2. The method according to claim 1, further comprising the above capacitor.
3. The semiconductor device according to claim 1. 3. The short circuit includes first to n-th capacitors, one of which is grounded (n is an integer of 2 or more); the other electrode of the first capacitor is Connected to the output electrode; the other electrode of the (k + 1) th capacitor is connected to the other electrode of the kth capacitor (k is any integer greater than or equal to 1 and less than or equal to (n-1)). The semiconductor device according to claim 1, wherein: 4. The semiconductor device according to claim 3, wherein the k-th capacitor has a smaller capacitance than the (k + 1) -th capacitor. 5. The short circuit includes one or more dielectric substrates, and one or more open stubs disposed on a surface of the dielectric substrate and connected to the output electrodes. 2. The semiconductor device according to claim 1, wherein: 6. The short circuit includes one or more dielectric substrates, two or more open stubs installed on a surface of the dielectric substrate, and one or two connecting the open stubs to the output electrode. 2. The semiconductor device according to claim 1, comprising the above microstrip line. 7. The short circuit includes one or more dielectric substrates, and two or more open stubs installed on a surface of the dielectric substrate and connected to the output electrodes independently of each other. The semiconductor device according to claim 1, wherein: