JP4172092B2 - Photoresponsive transistor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a photoresponsive transistor for converting an optical signal into an electric signal.
[0002]
[Prior art]
InP-based heterojunction phototransistors have been proposed as semiconductor light-receiving active elements that convert optical signals into electrical signals (Japanese Patent Laid-Open Nos. HEI 5-275730, H5-1304165, and H5-15). No. 95130). An example of this structure is shown in FIG. In FIG. 15, an n-type InP or n-type InGaAs layer 102, an n-type InGaAs layer 103, a p-type InGaAs layer 104, and an n-type InP or InGaAs layer 105 are sequentially stacked on an InP substrate 101. . The n-type InGaAs layer 103 serves as a collector portion of the transistor, and a collector electrode 106 is disposed on a part of the upper surface of the InGaAs layer 103. The p-type InGaAs layer 104 serves as a base portion of the transistor, and a base electrode 107 is disposed on a part of the upper surface of the InGaAs layer 104. Further, the n-type InP or InGaAs layer 105 serves as the emitter of the transistor, and an emitter electrode 108 is disposed on the upper surface of the InP or InGaAs layer 105. Each electrode 106, 107, 108 is in ohmic contact.
[0003]
[Problems to be solved by the invention]
However, in such a bipolar phototransistor, since p-type and n-type regions are formed, electron impurity scattering is large in the layer where electrons travel, and carrier mobility determined by physical properties of the bulk crystal is extremely high. Will become smaller. That is, there is a problem that high-speed operation is limited. Furthermore, since electrons and holes generated by light absorption are taken out as photocurrents, the sensitivity is low.
[0004]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a photoresponsive transistor capable of operating at high speed with respect to light with a new configuration and improving sensitivity performance.
[0005]
[Means for Solving the Problems]
According to the first aspect of the present invention, an electron storage layer and an electron supply layer made of a semiconductor having high electron mobility are disposed on a substrate, and a gate electrode that is in Schottky junction with the gate contact layer is disposed. A photoresponsive transistor that controls the number of electrons in the electron storage layer by a voltage applied to the semiconductor device, wherein a light absorbing semiconductor layer that absorbs predetermined light is disposed inside the gate contact layer. . According to a fourth aspect of the present invention, an electron storage layer and an electron supply layer made of a semiconductor having a high electron mobility are disposed, and a gate electrode that is in a Schottky junction is disposed on the gate contact layer. A photoresponsive transistor that controls the number of electrons in the electron storage layer by voltage, and a multi-quantum well structure for absorbing light is disposed inside the gate contact layer. It is characterized by.
[0006]
The heterojunction phototransistor according to claim 1 or 4 uses a high electron mobility transistor in which an electron supply layer and an electron storage layer are separated as a light receiving element, and carriers due to impurities in the electron storage layer. There is little scattering. In general, in a high electron mobility transistor, a depletion layer capacitance generated by a Schottky junction with a gate metal is controlled by a voltage applied to a gate electrode, and a radio signal is taken out as a change in drain current. When a radio wave signal having a certain frequency is incident on the electrode, the depletion layer capacitance immediately below the gate changes according to the cycle. Then, the change in the depletion layer can be extracted outside as the oscillation of the drain current.
[0007]
That is, if the voltage applied to the gate electrode can be modulated by light irradiation, a phototransistor effect for extracting radio waves to the outside can be generated.
[0008]
For this purpose, a high-speed phototransistor can be realized by inserting a light absorption layer that absorbs predetermined light into the gate contact layer of the photoresponsive transistor.
When light is incident on the transistor in which the light absorption layer is inserted, for example, as shown in FIG. 2, the light absorption semiconductor layer or the light absorption multilayer film absorbs the light and generates electrons and holes in the same region. The generated electrons and holes are immediately moved to the electron storage layer side and the holes are moved to the gate electrode side by the inclination of the energy band due to the Schottky junction and the gate applied voltage. However, both electrons and holes cannot reach the electron storage layer and the gate electrode due to the well-type potential of the gate contact layer and the light absorption semiconductor layer or the light absorption multilayer film, respectively. It is localized on the gate electrode side and the electron storage layer side of the absorbing multilayer film. Then, electrons and holes form negative space charges in those regions, and holes form positive space charges, and produce the same effect as when a positive voltage is applied to the gate electrode. That is, the number of electrons in the electron storage layer can be controlled. For example, when an intensity-modulated optical signal is irradiated, current oscillation occurs and radio waves can be extracted outside.
[0009]
In addition, since a photocurrent having a low sensitivity is not directly taken out to the outside but the Schottky level of the gate can be adjusted by the light intensity, a higher sensitivity can be expected as compared with a conventional bipolar phototransistor.
[0010]
In addition, since electron conduction with high mobility is used, the response to high-speed light modulation is high.
Here, as described in claim 2, in the photoresponsive transistor according to claim 1, the light absorption semiconductor layer has a forbidden band wider toward the gate electrode side. As described above, the light absorbing semiconductor layer is made of In. _1-x Ga _x It is practically preferable that the gate electrode is formed of As (x <0.7) and the x value increases toward the gate electrode side.
[0011]
Further, as described in claim 5, in the photoresponsive transistor according to claim 4, the multilayer film for light absorption has a wider forbidden band as the light absorption layer on the gate electrode side, As described in claim 6, the light absorbing multilayer film is made of In. _0.52 Al _0.48 As / In _1-x Ga _x It is practically preferable that the x value be larger as the gate electrode layer is formed of As (x <0.7).
[0012]
The gate contact layer and the light absorbing layer may be formed on at least one of the gate electrode side interface and the substrate side interface in the light absorbing semiconductor layer or the light absorbing multilayer film. It is practically preferable to dispose a barrier layer having a wider forbidden band than the semiconductor layer or the multilayer film for light absorption because carrier diffusion can be prevented.
[0013]
The barrier layer according to claim 9, wherein the barrier layer is In. _1-x Al _x It may be made of As (x> 0.48).
A reflection layer may be provided above the electron storage layer and below the light absorption semiconductor layer or the light absorption multilayer film according to claim 10 or 11, and According to a twelfth aspect of the invention, the reflective layer may be formed of a multilayer film, or, as in the thirteenth aspect, the multilayer film may have an InAs / AlAs heterojunction. Alternatively, as described in claim 14, the reflective layer may be a superlattice.
[0014]
In addition, as described in claim 15, an impurity doped layer can be disposed under the electron storage layer.
Further, as in the sixteenth and seventeenth aspects, the light absorbing semiconductor layer or the light absorbing multilayer film can be electrically cut off between the gate electrode and the source electrode and between the gate electrode and the drain electrode. . At this time, as in claim 18, it can be electrically cut off by the groove.
[0015]
According to a nineteenth aspect of the present invention, a high frequency transmission line for forming a light receiving circuit may be connected to the gate electrode, and a matching circuit including a stub for forming the light receiving circuit and a high frequency transmission line may be connected to the drain electrode side. In this way, for example, when irradiating intensity-modulated light, only a signal having a desired frequency can be extracted with high sensitivity.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
[0017]
FIG. 1 shows a cross-sectional view of the photoresponsive transistor in this embodiment.
On the semi-insulating InP substrate 11, i-In _0.52 Al _0.48 I-In made of a semiconductor having an As buffer layer 12 stacked thereon and a high electron mobility. _0.80 Ga _0.20 An As electron storage layer 13 is stacked. The electron storage layer 13 is made of In. _0.53 Ga _0.47 As may be used. On the electron storage layer 13, i-In _0.52 Al _0.48 An As layer 15 is laminated. However, i-In _0.52 Al _0.48 An electron supply layer (δ-doped layer) 14 that is δ-doped with Si is disposed in the As layer 15. The δ-doped layer 14 may be formed below the electron storage layer 13. In addition, i-In _0.52 Al _0.48 On the As layer 15, for example, i-In serving as a light absorption layer for infrared light having a wavelength of 1.55 μm. _0.53 Ga _0.47 An As layer 16 is laminated. On this light absorbing semiconductor layer 16, i-In _0.52 Al _0.48 An As layer 17 is laminated.
[0018]
Thus, in this embodiment, i-In _0.52 Al _0.48 As layer 15 and i-In _0.52 Al _0.48 A gate contact layer is configured by the As layer 17, and a light absorbing semiconductor layer 16 that absorbs predetermined light is disposed inside the gate contact layers 15 and 17.
[0019]
i-In _0.52 Al _0.48 On the As layer 17 is n-type In. _0.53 Ga _0.47 A cap layer 18 made of As is laminated. A source electrode 20 and a drain electrode 22 are formed on the upper surface of the cap layer 18 so as to exhibit ohmic characteristics. The gate electrode 19 is etched by etching the cap layer 18 so as to form a Schottky junction. _0.52 Al _0.48 It is in contact with the As gate contact layer 17. The number of electrons in the electron storage layer 13 can be controlled by the voltage applied to the gate electrode 19.
[0020]
The portions other than the electrode portions are covered with an insulating film 21 such as silicon nitride or silicon oxide.
In contrast to the InP-based heterojunction phototransistor shown in FIG. 15, the heterojunction phototransistor (photoresponsive transistor as a light receiving element) in FIG. 1 has an electron supply layer 14 and an electron storage layer 13 separated from each other. In addition, carrier scattering due to impurities in the electron storage layer 13 is small, and high-speed operation with respect to light is possible.
[0021]
Here, in this example, when absorbing a predetermined light between the gate contact layers 15 and 17 of the photoresponsive transistor, for example, when absorbing an infrared light of 1.55 μm used in optical communication, In _0.53 Ga _0.47 An As light absorbing semiconductor layer 16 is inserted to form a high-speed phototransistor.
[0022]
FIG. 2 shows a band diagram of the conduction band and the valence band of the photoresponsive transistor according to the first embodiment of the present invention.
When infrared light having a wavelength of 1.55 μm is incident on the photoresponsive transistor from the gate surface side, the photon energy is about 0.8 eV. Therefore, in the stacked semiconductors, the forbidden band width is 0.8 eV or less. An n-type In _0.53 Ga _0.47 As light absorbing semiconductor layer 16 and i-In _0.80 Ga _0.20 It is intended to be absorbed by the As electron storage layer 13. Where i-In _0.80 Ga _0.20 When light is absorbed in the As electron storage layer 13, holes with low mobility are generated in the electron storage layer 13 together with electrons, and high-speed operability decreases. Therefore, in this example, n-type In is used so that light is hardly absorbed by the electron storage layer 13. _0.53 Ga _0.47 The thickness of the As light absorbing semiconductor layer 16 is adjusted according to the intensity of incident light.
[0023]
When light is absorbed in the light absorption semiconductor layer 16, electrons and holes are generated in the light absorption semiconductor layer 16. The generated electrons and holes are immediately transferred to the electron storage layer 13 side of the light absorption semiconductor layer 16 by the inclination of the energy bands of the conduction band and the valence band due to the Schottky junction and the gate applied voltage, and the holes are light The semiconductor layer 16 for absorption moves to the gate electrode 19 side. However, both electrons and holes are caused by the band discontinuity between the light absorbing semiconductor layer 16 and the gate contact layer 17 and the band discontinuity between the light absorbing semiconductor layer 16 and the gate contact layer 15, respectively. Cannot reach the gate electrode 19 and is localized on the gate electrode 19 side and the electron storage layer 13 side in the light absorption semiconductor layer 16.
[0024]
Then, electrons and holes form negative space charges in these regions, electrons form negative space charges, and holes form positive space charges. Therefore, as shown by a broken line in FIG. 2, the inclination of the conduction band and the valence band changes in a direction of relaxation.
[0025]
As a result, the depletion layer capacitance immediately below the gate electrode 19 increases, and the number of electrons in the electron storage layer 13 increases. That is, the same effect as when a positive voltage is applied to the gate electrode 19 is produced, and the drain-source current increases. That is, the number of electrons in the electron accumulation layer 13 can be controlled. For example, when an intensity-modulated infrared light signal is irradiated, current oscillation occurs, and radio waves can be extracted outside.
[0026]
In this case, since the electron mobility in the electron accumulation layer 13 is extremely high reflecting the effective mass of electrons in the same region, high-speed operation is possible. In other words, a photocurrent having a low sensitivity is not directly taken out to the outside, but the Schottky level of the gate can be adjusted by the light intensity, so that a higher sensitivity can be expected as compared with a conventional bipolar phototransistor.
[0027]
Thus, the present embodiment has the following features.
(A) The high electron mobility transistor is a photoresponsive transistor, and the light absorption semiconductor layer 16 that absorbs predetermined light is disposed inside the gate contact layers 15 and 17. Therefore, the scattering of carriers due to impurities in the electron storage layer 13 is small, and by inserting the light absorbing semiconductor layer 16 that absorbs predetermined light into the gate contact layers 15 and 17, the electrons and holes are absorbed. The semiconductor layer 16 is localized on the gate electrode 19 side and the electron storage layer 13 side to form positive and negative space charges, the number of electrons in the electron storage layer 13 can be controlled, and the intensity-modulated optical signal is converted into a current. Radio waves can be extracted outside as vibrations. Further, since the photocurrent having a low sensitivity is not directly taken out to the outside but the Schottky level of the gate can be adjusted by the light intensity, a higher sensitivity can be obtained as compared with the conventional bipolar phototransistor. In this way, it is possible to operate at high speed with respect to light and improve sensitivity performance.
(Second Embodiment)
Next, the second embodiment will be described focusing on the differences from the first embodiment.
[0028]
FIG. 3 is a cross-sectional view of the photoresponsive transistor (high electron mobility phototransistor) according to this embodiment. Members having the same functions and configurations as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.
[0029]
In this embodiment, i-In in FIG. _0.53 Ga _0.47 Instead of the As light absorbing semiconductor layer 16, a light absorbing semiconductor layer 25 is used. As shown in FIG. 4, the light absorbing semiconductor layer 25 has a forbidden band width Eg that is wider toward the gate electrode 19 side. Specifically, as shown in FIG. _1-x Ga _x It is formed of As (x <0.7), and the x value increases toward the gate electrode 19 side.
[0030]
Specifically, In, which is a semiconductor layer for light absorption _1-x Ga _x The composition x of the As layer is changed from x = 0.20 to 0.70 toward the surface of the gate electrode 19 side. In other words, In _1-x Ga _x The composition x of the As layer 25 is changed from x = 0.20 to 0.70 toward the surface side to increase the band slope of the conduction band.
[0031]
Since the mobility of the electron storage layer 13 is extremely high as described above, the responsiveness to the incident modulated light influences the speed at which space charges induced in the gate contact layers 15 and 17 are formed. is there. In the second embodiment of the present invention, by increasing the band slope of the conduction band, i-In _0.52 Al _0.48 The time for forming the negative space charge generated in the upper layer of the As layer 15 can be shortened.
[0032]
Thus, the present embodiment has the following features.
(A) The light absorbing semiconductor layer 25 is In _1-x Ga _x By forming As (x <0.7) and increasing the x value toward the gate electrode 19 side, the forbidden band width Eg becomes wider toward the gate electrode 19 side, so that the responsiveness can be improved.
(Third embodiment)
Next, the third embodiment will be described with a focus on differences from the first embodiment.
[0033]
FIG. 6 shows a cross-sectional view of the photoresponsive transistor (high electron mobility phototransistor) according to this embodiment. Members having the same functions and configurations as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.
[0034]
In this embodiment, a light absorption multilayer film 31 having a multiple quantum well structure is used instead of the light absorption semiconductor layer 16 of FIG. That is, the multilayer film 31 for light absorption having a multiple quantum well structure for absorbing predetermined light is disposed inside the gate contact layers 15 and 17.
[0035]
Specifically, the multilayer film 31 for light absorption is i-In forming a gate contact layer. _0.52 Al _0.48 In the As layers 15 and 17, as shown in FIG. _0.53 Ga _0.47 As layers 31a, 31b, 31c, 31d and i-In _0.52 Al _0.48 A multi-quantum well structure (MQW) is formed by alternately stacking As layers 31e, 31f, and 31g.
[0036]
By the way, in order to output a high-frequency signal in accordance with light subjected to high-speed intensity modulation, i-In _0.52 Al _0.48 Lower layer of As gate contact layer 17 and i-In _0.52 Al _0.48 Space charges due to electrons and holes attracted to the upper layer side of the As gate contact layer 15 must be induced at high speed and disappear. For this purpose, the recombination speed of electrons and holes must be increased to some extent. Here, in this embodiment, the light absorption multilayer film 31 has an MQW structure, thereby improving the recombination speed of electrons and holes.
[0037]
As shown in FIG. 7, the electrons and holes generated in the light absorption multilayer film 31 are attracted to the opposite sides spatially due to the inclination of the conduction band and the valence band. However, since the multilayer film 31 for light absorption has an MQW structure, the recombination speed of electrons and holes is fast, and an output signal that follows that is obtained when light whose intensity is modulated at high speed is irradiated.
[0038]
Thus, the present embodiment has the following features.
(A) Since the multilayer film 31 for light absorption having a multiple quantum well structure for absorbing predetermined light is arranged inside the gate contact layers 15 and 17, the same action and effect as in the first embodiment are provided. It is possible to operate at high speed with respect to light and to improve sensitivity performance.
[0039]
Also in this embodiment, as described in the second embodiment, the light absorption multilayer film 31 (i-In _0.53 Ga _0.47 As layers 31a to 31d and i-In _0.52 Al _0.48 As layers 31e to 31g), the light absorption layers 31a to 31d on the gate electrode side have wider forbidden band widths Eg. Specifically, In layers 31e to 31g) _0.52 Al _0.48 As / In _1-x Ga _x It can be formed of As (x <0.7), and the layer on the side of the gate electrode 19 has a larger x value.
(Fourth embodiment)
Next, the fourth embodiment will be described with a focus on differences from the first embodiment.
[0040]
FIG. 8 is a cross-sectional view of the photoresponsive transistor (high electron mobility phototransistor) according to this embodiment. Members having the same functions and configurations as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.
[0041]
In the present embodiment, the forbidden band width Eg is wider than the gate contact layers 15 and 17 and the light absorption semiconductor layer 16 at the gate electrode 19 side interface portion and the substrate 11 side interface portion in the light absorption semiconductor layer 16 of FIG. Barrier layers 41 and 42 are disposed (see FIG. 9).
[0042]
Specifically, i-In _0.52 Al _0.48 An AlAs barrier layer 41 is laminated on the As gate contact layer 15. AlAs is i-In _0.53 Ga _0.47 The forbidden bandwidth Eg is larger than As. On the barrier layer 41, i-In _0.53 Ga _0.47 An As light absorbing semiconductor layer 16 is stacked. Further, an AlAs barrier layer 42 is laminated on the light absorbing semiconductor layer 16. I-In on the barrier layer 42 _0.52 Al _0.48 An As gate contact layer 17 is stacked.
[0043]
As shown in FIG. 9, the AlAs barrier layers 41 and 42 form a potential barrier that prevents electrons and holes from flowing into the electron storage layer 13 and the gate electrode 19 due to thermal diffusion and tunneling, respectively. Therefore, the space charge due to electrons and holes is increased, and the modulation sensitivity to the current in the electron storage layer 13 is high. I _- In _0.52 Al _0.48 The number of carriers traveling in the As gate contact layers 15 and 17 is reduced, and there is an advantage that the breakdown voltage of the transistor is improved.
[0044]
Note that only one of the barrier layers 41 and 42 may be provided.
Thus, the present embodiment has the following features.
(A) A barrier layer having a wider forbidden band than the gate contact layers 15 and 17 and the light absorbing semiconductor layer 16 on at least one of the gate electrode 19 side interface and the substrate 11 side interface in the light absorbing semiconductor layer 16 Since 41 and 42 are disposed, the modulation sensitivity can be increased.
[0045]
The barrier layers 41 and 42 are made of In _1-x Al _x It may be made of As (x> 0.48).
Further, this configuration may be applied in the third embodiment. That is, the forbidden band width at least one of the gate electrode 19 side interface portion and the substrate 11 side interface portion in the light absorption multilayer film 31 of FIGS. 6 and 7 is larger than that of the gate contact layers 15 and 17 and the light absorption multilayer film 31. A wide barrier layer may be disposed.
(Fifth embodiment)
Next, the fifth embodiment will be described focusing on the differences from the first embodiment.
[0046]
FIG. 10 is a cross-sectional view of the photoresponsive transistor (high electron mobility phototransistor) according to this embodiment. Members having the same functions and configurations as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.
[0047]
In the present embodiment, the reflective layer 51 is provided above the electron storage layer 13 of FIG. 1 and below the light absorption semiconductor layer 16.
Specifically, an InAs / AlAs heterojunction superlattice layer 51 is laminated on the electron storage layer 13. That is, the reflective layer 51 is a multilayer film, has an InAs / AlAs heterojunction, and is a superlattice. On top of that is In _0.52 Al _0.48 As gate contact layer 15, i-In _0.53 Ga _0.47 An As light absorbing semiconductor layer 16 is stacked.
[0048]
For example, when infrared light having a wavelength of 1.55 μm with a photon energy of 0.8 eV is irradiated from the surface, the electron storage layer 13 absorbs light because the band gap is smaller than that. However, when light absorption occurs in the electron storage layer 13, holes with low mobility are generated together with electrons, and the high speed performance is reduced. Here, in the present embodiment, the light incident from the gate surface is reflected by the multilayer film (superlattice) layer 51 that is an InAs / AlAs heterojunction disposed above the electron storage layer 13 and is absorbed by the electron storage layer 13. Will not be. That is, due to the difference in refractive index between InAs and AlAs, light incident from the gate surface is reflected by the multilayer film (superlattice) layer 51, and light absorption other than the light absorption semiconductor layer 16 is suppressed.
[0049]
Thus, the present embodiment has the following features.
(A) Since the reflective layer 51 is provided above the electron storage layer 13 and below the light absorption semiconductor layer 16, it is difficult to generate holes.
[0050]
This configuration may be applied in the third embodiment. That is, a reflective layer may be provided above the electron storage layer 13 of FIG. 6 and below the light absorption multilayer film 31.
(Sixth embodiment)
Next, the sixth embodiment will be described with a focus on differences from the first embodiment.
[0051]
FIG. 11 is a cross-sectional view showing a photoresponsive transistor (high electron mobility phototransistor) according to this embodiment. Members having the same functions and configurations as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.
[0052]
As shown in FIGS. 11 and 12, i-In _0.52 Al _0.48 An impurity doped layer 61 δ-doped with Si is disposed inside the As buffer layer 12. As described above, by arranging the δ-doped impurity doped layer 61 under the electron storage layer 13, electrons can be easily supplied to the electron storage layer 13.
[0053]
This can also be applied to other embodiments (for example, the third embodiment).
(Seventh embodiment)
Next, the seventh embodiment will be described with a focus on differences from the first embodiment.
[0054]
FIG. 13 is a cross-sectional view of the photoresponsive transistor (high electron mobility phototransistor) according to this embodiment. Members having the same functions and configurations as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted.
[0055]
In the present embodiment, the light absorption semiconductor layer 16 is electrically cut off by forming deep grooves 71 between the gate electrode 19 and the source electrode 20 and between the gate electrode 19 and the drain electrode 22. .
[0056]
Specifically, the semiconductor layers 16, 17 and 18 between the gate electrode 19 and the source electrode 20 and between the gate electrode 19 and the drain electrode 22 are removed by etching, and i-In _0.53 Ga _0.47 Electrons generated in the As light absorbing semiconductor layer 16 flow between the drain and source, between the gate and source, and the like so that the region does not become a subchannel.
[0057]
This configuration may be applied in the third embodiment. That is, the light absorption multilayer film 31 may be electrically cut off between the gate electrode 19 and the source electrode 20 and between the gate electrode 19 and the drain electrode 22 in FIG.
(Eighth embodiment)
Next, an eighth embodiment will be described focusing on differences from the first to seventh embodiments.
[0058]
FIG. 14 shows a semiconductor light receiving circuit in the present embodiment. For example, a coplanar type high-frequency transmission line 81 is connected to the gate electrode of the photoresponsive transistor (high electron mobility phototransistor) 80 described in the first to seventh embodiments. Further, an output matching circuit 84 composed of a coplanar type high frequency transmission line 82 and a stub 83 is connected to the drain electrode. Furthermore, capacitors 85 and 86 are connected to the stub 83 and the transmission line 81 for grounding high-frequency signals. Each of these elements 80, 81, 82, 83, 85, 86 is formed on the same substrate.
[0059]
Each element 80, 81, 82, 83, 85, 86 may be formed on each chip to be a hybrid type.
Thus, if the transmission line 81 is connected to the gate side, the sensitivity of the radio signal taken out from the output port can be increased. For example, when intensity modulation of incident light is performed, a desired frequency signal can be extracted with high sensitivity by connecting the output matching circuit 84 to the drain side.
[0060]
Further, in FIG. 15, the semiconductor film has to be complicated to form the base electrode 107 and the collector electrode 106, and there is a problem that integration with other devices is difficult. On the other hand, in the present embodiment, the consistency of the phototransistor with other devices can be ensured. That is, it is not necessary to form a p-type impurity region as in the conventional phototransistor, and there is an advantage that the compatibility with other devices is good and the integration is easy.
[0061]
Thus, the present embodiment has the following features.
(A) A high-frequency transmission line 81 for forming a light receiving circuit is connected to the gate electrode, and a matching circuit 84 including a stub 83 for forming the light receiving circuit and a high-frequency transmission line 82 is connected to the drain electrode side. Therefore, for example, when intensity-modulated light is irradiated, only a signal having a desired frequency can be extracted with high sensitivity.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a photoresponsive transistor according to a first embodiment.
FIG. 2 is a band diagram of the photoresponsive transistor according to the first embodiment.
FIG. 3 is a schematic cross-sectional view showing a photoresponsive transistor according to a second embodiment.
FIG. 4 is a band diagram of a photoresponsive transistor according to a second embodiment.
FIG. 5 is a diagram for explaining a composition distribution of a film.
FIG. 6 is a schematic cross-sectional view showing a photoresponsive transistor according to a third embodiment.
FIG. 7 is a band diagram of a photoresponsive transistor according to a third embodiment.
FIG. 8 is a schematic cross-sectional view showing a photoresponsive transistor according to a fourth embodiment.
FIG. 9 is a band diagram of a photoresponsive transistor according to a fourth embodiment.
FIG. 10 is a schematic cross-sectional view showing a photoresponsive transistor according to a fifth embodiment.
FIG. 11 is a schematic cross-sectional view showing a photoresponsive transistor according to a sixth embodiment.
FIG. 12 is a band diagram of a photoresponsive transistor according to a sixth embodiment.
FIG. 13 is a schematic cross-sectional view showing a photoresponsive transistor according to a seventh embodiment.
FIG. 14 is a schematic cross-sectional view showing a photoresponsive transistor according to an eighth embodiment.
FIG. 15 is a diagram for explaining a conventional technique.
[Explanation of symbols]
11 ... Semi-insulating InP substrate, 13 ... i-In _0.80 Ga _0.20 As electron storage layer, 14 ... electron supply layer (δ-doped layer), 15 ... i-In _0.52 Al _0.48 As gate contact layer, 16 ... light absorption semiconductor layer, 17 ... In _0.53 Ga _0.47 As gate contact layer, 19 ... gate electrode, 25 ... light absorption semiconductor layer, 31 ... light absorption multilayer film, 41, 42 ... barrier layer, 51 ... reflection layer, 61 ... impurity doped layer, 81, 82 ... coplanar type High-frequency transmission line, 83... Stub, 84.

Claims (19)

An electron storage layer and an electron supply layer made of a semiconductor having a high electron mobility are disposed on the substrate, and a gate electrode that is in Schottky junction is disposed on the gate contact layer, and the electron storage layer is applied by a voltage applied to the gate electrode. A photoresponsive transistor that controls the number of electrons in the device,
A light-responsive transistor characterized in that a light-absorbing semiconductor layer that absorbs predetermined light is disposed inside the gate contact layer. 2. The photoresponsive transistor according to claim 1, wherein the light absorption semiconductor layer has a forbidden band wider toward a gate electrode side. 3. The optical response according to claim 2, wherein the semiconductor layer for light absorption is formed of In _1-x Ga _x As (x <0.7), and an x value increases toward the gate electrode side. Type transistor. An electron storage layer and an electron supply layer made of a semiconductor having a high electron mobility are disposed on the substrate, and a gate electrode that is in Schottky junction is disposed on the gate contact layer, and the electron storage layer is applied by a voltage applied to the gate electrode. A photoresponsive transistor that controls the number of electrons in the device,
A photoresponsive transistor characterized in that a multilayer film for light absorption having a multiple quantum well structure for absorbing predetermined light is disposed inside the gate contact layer. The photoresponsive transistor according to claim 4, wherein the light absorption multilayer film has a wider forbidden band as the light absorption layer on the gate electrode side. The multilayer film for light absorption is formed of In _0.52 Al _0.48 As / In _1-x Ga _x As (x <0.7), and the x value is larger toward the gate electrode side layer. The photoresponsive transistor according to claim 5. The barrier layer having a wider forbidden band than the gate contact layer and the light absorbing semiconductor layer is disposed on at least one of the gate electrode side interface and the substrate side interface in the light absorbing semiconductor layer. Item 2. The photoresponsive transistor according to Item 1. The gate contact layer and a barrier layer having a wider forbidden band than that of the light absorption multilayer film are disposed on at least one of the gate electrode side interface and the substrate side interface in the light absorption multilayer film. Item 5. The photoresponsive transistor according to Item 4. 9. The photoresponsive transistor according to claim 7, wherein the barrier layer is made of In _1-x Al _x As (x> 0.48). 2. The photoresponsive transistor according to claim 1, wherein a reflective layer is provided above the electron storage layer and below the light absorbing semiconductor layer. 5. The photoresponsive transistor according to claim 4, wherein a reflective layer is provided above the electron storage layer and below the light absorption multilayer film. The photoresponsive transistor according to claim 10, wherein the reflective layer is formed of a multilayer film. 13. The photoresponsive transistor according to claim 12, wherein the multilayer film has an InAs / AlAs heterojunction. The photoresponsive transistor according to claim 12, wherein the reflective layer is a superlattice. The photoresponsive transistor according to claim 1, wherein an impurity-doped layer is disposed under the electron storage layer. 2. The photoresponsive transistor according to claim 1, wherein the light absorption semiconductor layer is electrically cut off between the gate electrode and the source electrode and between the gate electrode and the drain electrode. 5. The photoresponsive transistor according to claim 4, wherein the multilayer film for light absorption is electrically cut off between the gate electrode and the source electrode and between the gate electrode and the drain electrode. 18. The photoresponsive transistor according to claim 16, wherein the photoresponsive transistor is electrically cut off by a groove. 19. A high frequency transmission line for forming a light receiving circuit is connected to the gate electrode, and a matching circuit comprising a stub for forming the light receiving circuit and a high frequency transmission line is connected to the drain electrode side. The photoresponsive transistor according to Item.

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