JP5740125B2 - Semiconductor light emitting device - Google Patents

Description

The present invention relates to a semiconductor light emitting element used in the optical wiring and the like.

Along with the recent high integration of LSIs, the miniaturization of circuits inside the LSIs is progressing. With this miniaturization, the wiring cross-sectional area is reduced and the distance between adjacent wirings is reduced. Therefore, the wiring resistance inside the LSI increases and the capacitance between the wirings increases. As a result, the wiring delay time determined by the wiring resistance and the wiring capacitance increases, and it is difficult to further increase the speed of the LSI. Optical wiring technology has attracted attention as a technology for solving the wiring delay problem associated with high integration of LSIs. Optical wiring technology is a method of transmitting optical signals using optical waveguides, and does not increase the wiring resistance and inter-wiring capacitance due to the miniaturization as described above, and can be expected to further increase the operation speed. . An opto-electric hybrid LSI has been proposed as an LSI that performs signal transmission using such an optical wiring. An opto-electric hybrid LSI is an LSI using a method in which signal processing by each functional block is performed electrically, and an optical signal is transmitted between these functional blocks. Such an opto-electric hybrid LSI requires an element that converts an electric signal subjected to signal processing into an optical signal, that is, a light emitting element. As an integrated form of the light emitting element, a laser structure is formed by wafer bonding on the top of the optical waveguide (Non-patent Document 1), and the optical waveguide and the laser structure are bonded via an organic film (Non-patent Document 2). ), And those mounted directly on the Si substrate (Patent Document 1). Since the structure described in Non-Patent Document 1 has an air layer below the laser structure, it is difficult to efficiently dissipate the heat generated in the laser part, and good temperature characteristics are not obtained. Moreover, since the structure described in Non-Patent Document 2 has a laser element formed on the organic film, heat dissipation is poor and good temperature characteristics cannot be obtained. Further, these conventional elements are large in size and need to be miniaturized in order to be integrated on an LSI chip. Currently, along with the rapid progress of information communication, studies are being made to reduce the size of the element for the introduction of optical wiring into an LSI for large-scale integration. As a method for improving a conventional optical waveguide technique for confining light using a difference in refractive index, application of a polariton waveguide has been proposed (Non-Patent Document 1). This utilizes a wave propagating through the interface while being localized at the interface between the metal and the dielectric, and is different in principle from a conventional hollow waveguide using metal reflection. A wave propagating on the surface is a kind of electromagnetic wave, and is called a surface plasmon polariton (SurfaconePlaasmonPollanit: SPPP) wave. Polariton waveguides using metals or semiconductors as the negative dielectric constant side material can be applied to visible light and communication wavelength bands, but have a problem that propagation loss is large and efficiency is not so high. In recent years, by forming a nanorod structure of CdS semiconductor on a dielectric film / metal Ag film, an SPP wave is generated at the interface of the dielectric, and propagation loss is reduced by hybridization with the optical waveguide mode of the nanorod structure of CdS semiconductor. And we succeeded in laser oscillation with optical excitation. However, like the conventional laser, the heat dissipation of the element structure is poor, the oscillation is limited to extremely low temperature (4K), and the current driving method is difficult, and the element structure is not suitable for practical use and mass production. Improvement is desired.

Japanese Patent No. 3391521

Optics Express, Vol. 14, Issue 20, pp. 9203-9210 Optics Express, Vol. 14, Issue 18, pp. 8154-8159

The present invention has been made in view of the above problems, and an object of the present invention is to provide a semiconductor light-emitting element that has excellent heat dissipation and can be stably operated .

The semiconductor light-emitting device of this embodiment includes a Si substrate, a semiconductor light-emitting layer that forms a light-emitting device made of a compound semiconductor containing Ga, and a dielectric formed on the semiconductor light-emitting layer. A carbon nanotube bundle formed on the top surface of the dielectric layer and including a plurality of carbon nanotubes, and an optical waveguide structure formed between the bottom surface of the dielectric layer and the semiconductor light emitting layer. Each of the plurality of carbon nanotubes has a long axis direction length of 10 μm and a diameter of 1 nm to 100 nm, and the carbon nanotube bundle has a space filling factor of 50% or more. wherein the carbon nanotube bundles, the dielectric layer in contact with said by light having a peak wavelength of 650nm from the semiconductor light-emitting layer dielectric layer and the front To generate a surface plasmon polaritons at the interface between the carbon nanotube bundles.

BRIEF DESCRIPTION OF THE DRAWINGS The figure explaining Example 1 of this invention. The figure explaining Example 2 of this invention. The figure explaining Example 1 and 2 of this invention.

 Details of the present invention will be described below with reference to embodiments shown in the drawings. Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment, It can be used with various devices.

(First embodiment)
1A and 1B are views showing an embodiment of the present invention, in which FIG. 1A is a sectional view and FIG. 1B is a top view. P-type contact layer in this order from below on the Si substrate 1, InAlAs cladding layer (referred to as a p-type semiconductor layer 2 are collectively in FIG. 1 the contact layer and the cladding layer), InAlAs / InGaAs multiple quantum well layer 3, InAlAs cladding layer, A compound semiconductor laser portion comprising an n-type InGaAs contact layer, InAlAs cladding layer, InGaAs guide layer (in FIG. 1, the cladding layer, contact layer, and guide layer are collectively referred to as an n-type semiconductor layer 4) , a dielectric comprising SiO 2 Layer 5 is formed. In the laser part, p-type and n-type ohmic electrodes 6 and 7 are formed. Carbon nanotubes (CNT) 8 are formed on the SiO2 layer.

For the semiconductor light emitting layer, a gallium arsenide (GaAs) substrate was used, and a necessary laminated structure was formed by metal organic chemical vapor deposition (MOCVD). An n-type AlGaInP clad layer, a GaInP / AlGaInP multiple quantum well active layer, and a p-type AlGaInP clad layer were stacked on an n-GaAs substrate. The PL (Photo-Luminescence) peak wavelength from the multiple quantum well structure of the active layer was adjusted to be a red wavelength of about 650 nm. Thereafter, the MOCVD laminated wafer was bonded onto the Si substrate, and the n-GaAs substrate portion was removed by etching. Thereafter, a ridge waveguide structure was formed by dry etching, and then a dielectric film and a SiO2 film were formed to a thickness of 3 to 5 nm. For the electrode portion, the dielectric film was removed to form p-type and n-type ohmic electrodes, respectively. Thereafter, the production of CNTs was performed according to the following procedure. First, a metal (Co, Fe, Ni, etc.) serving as a catalyst was deposited on the side wall surface of the underlayer 100 , and then the unnecessary portion of the catalyst / underlayer 100 was removed by oblique milling. Thereafter, CNTs are selectively grown on the catalyst / underlayer 100 by plasma CVD, and CNTs having a length of about 10 μm in the lateral direction are formed with nanorods having a diameter of 1-100 nm and an aspect ratio of 10 or more with a space filling ratio of 50% or more. (See FIG. 3).

  In the light-emitting device fabricated in this way, surface plasmon polaritons are generated at the interface between the dielectric layer and the CNT, light is confined below the light wavelength, and high electric field strength is obtained, which is difficult to drive by current. Room temperature oscillation at a wavelength of 650 nm was obtained by the method. Since the light-emitting element is formed on the Si substrate, it has excellent heat dissipation and can be operated at room temperature. As a result, it is expected to realize a highly efficient and low energy consumption optical wiring device in which a light emitting element and a waveguide are integrated.

  In this embodiment, the active layer of the semiconductor light emitting layer has been described using an InGaAlP system. However, the present invention is not limited thereto, and various materials such as a GaInAs (N) system, an AlGaAs system, an InGaAsP system, and an InGaN system can be used. . Similarly, various materials can be used for the clad layer. Further, in the present embodiment, description has been made mainly using cylindrical CNTs as the desired shape, but it is clear that the present invention is also effective in shapes such as squares, rectangles, and ellipses. . The shape of the underlayer is preferably a vertically long rectangle or a reverse mesa structure in that the contact area between the CNT bundle and the lower dielectric layer can be reduced and the CNT density can be increased. For the growth of CNTs, the plasma CVD method is used here, but a thermal CVD method may be used. Thermal or plasma CVD is desirable from the viewpoints of growth site selectivity, growth temperature range, mass productivity, and the like. Further, in order to reduce the contact area between the CNT bundle and the dielectric layer on the lower surface and increase the CNT density, the shape of the underlayer is preferably a vertically long rectangle or a reverse mesa. As a method for producing CNTs, there is a method in which a CNT bundle is selectively grown and then the CNT bundle is tilted by immersion in a solution. If the selective growth region is made circular, it becomes a cylindrical CNT bundle after solution immersion, and can be brought into contact with the dielectric surface with a minimum area. As the solution, water, alcohol or the like is preferable in consideration of damage to the CNT. Although the SiO2 film is used here as the dielectric, it is obvious that the same effect can be obtained even if other materials such as SiN, SiON, MgF2 are used.

 According to the present invention, the semiconductor light emitting layer (III-V) is disposed on the Si substrate, the semiconductor light emitting layer has a current injection portion, and the interface between the dielectric layer and the carbon nanotube or the graphene layer by light emission of the semiconductor. It is an element characterized by generating surface plasmon polaritons, and an ultra-small current injection type light-emitting element can be realized. Further, since the light emitting element is formed on the Si substrate, the heat dissipation is excellent and stable operation is possible. Thereby, a highly efficient and low energy consumption optical wiring device in which the light emitting element and the waveguide are integrated can be provided.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. 2A and 2B are views showing an embodiment of the present invention, in which FIG. 2A is a sectional view and FIG. 2B is a top view. Elements similar to those described above with reference to FIGS. 1 and 3 are given the same reference numerals, and detailed descriptions thereof are omitted. The difference here is that one electrode 7 is formed on the Si substrate surface. It can be manufactured by bonding the semiconductor light emitting layer after performing electrode formation before wafer bonding. Other steps are the same as those in the first embodiment. Even in the light-emitting device fabricated in this manner, surface plasmon polaritons are generated at the interface between the dielectric layer 5 and the CNT 8 , light is confined below the light wavelength, and high electric field strength is obtained. Room-temperature oscillation at a wavelength of 650 nm was obtained by the current driving method.

1 Si substrate 2 p- type semiconductor layer 3 semiconductor light emitting layer 4 n- type semiconductor layer 5 dielectric 6 n- electrode 7 p- electrode 8 CNT
10 Laser light

Claims (4)

A semiconductor light emitting layer constituting a light emitting element made of a compound semiconductor containing Ga, formed on the Si substrate, and a Si substrate;
A dielectric layer formed on the semiconductor light emitting layer;
A carbon nanotube bundle formed on an upper surface of the dielectric layer and including a plurality of carbon nanotubes ;
An optical waveguide structure formed between the bottom surface of the dielectric layer and the semiconductor light emitting layer;
Comprising
Each of the plurality of carbon nanotubes has a long axis direction of 10 μm and a diameter of 1 nm-100 nm,
The carbon nanotube bundle includes the plurality of carbon nanotubes at a space filling rate of 50% or more,
The carbon nanotube bundle is in contact with the dielectric layer,
Generating surface plasmon polaritons at the interface between the dielectric layer and the carbon nanotube bundle by light having a peak wavelength of 650 nm from the semiconductor light emitting layer;
A semiconductor light emitting element characterized by the above.   The semiconductor light emitting device according to claim 1, wherein the light emitting device has a current injection portion on the semiconductor light emitting layer.   2. The semiconductor light emitting device according to claim 1, wherein a part of the dielectric layer is etched, and an electrode is formed in contact with the semiconductor light emitting layer exposed by the etching. Each of the plurality of carbon nanotubes has an aspect ratio of 10 or more.
The semiconductor light-emitting device according to claim 1, wherein

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