JP2009182296A - Light emitting element and integrated element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve light emission efficiency in a light emitting element of a structure where quantum dot comprising direct transition type group III-V compound semiconductor are embedded in a group IV semiconductor embedding layer. <P>SOLUTION: The light emitting element includes: a substrate 1 containing Si; and an active layer 2 formed on the substrate 1. The active layer 2 includes quantum dot 5 each comprising a direct transition type group III-V compound semiconductor material; an outer shell part 6 for covering the entire surface of the quantum dot 5; and group IV semiconductor embedding layer 3 for embedding the quantum dot 5 covered with the outer shell part 6. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a light emitting element and an integrated element which are formed on a substrate made of a silicon-based material such as a Si substrate and are suitable for use in a light emitting element having quantum dots.

In recent years, a light-emitting element (light-emitting device) that can be monolithically integrated on a silicon (Si) substrate has been demanded for application to optical wiring between chips or between boards.
In particular, in consideration of luminous efficiency, it is desirable to form a light emitting element made of a direct transition type III-V group compound semiconductor on a Si substrate.
However, for example, when an active layer (two-dimensional continuous film) having a quantum well structure made of a III-V group compound semiconductor is grown on a Si substrate, an antiphase domain (a region whose polarity is reversed in the plane) or lattice mismatch As a result, crystal defects were generated due to the distortion of the light emitting element, and a light emitting device having good crystallinity could not be obtained.

For this reason, a light emitting device having a structure in which quantum dots made of a direct transition type III-V compound semiconductor are embedded in a SiGeC layer (group IV semiconductor layer; buried layer) formed on a Si substrate has been proposed. (See Patent Document 1).
WO2006 / 085361

However, in the light emitting device having the structure described in Patent Document 1 described above, the interface between the quantum dot and the buried layer in which the quantum dot is embedded is a III-V group compound semiconductor / IV group semiconductor interface. As a result, it was found that the group IV semiconductor impurity concentration inside the quantum dot increased, and the luminous efficiency decreased.
Further, since the energy level of the direct transition conduction band of the III-V compound semiconductor quantum dot is relatively close to the energy level of the indirect transition conduction band of the group IV semiconductor buried layer (the energy level difference is small), It was found that the quantum confinement effect was not obtained and the temperature characteristics of the luminous efficiency were affected.

  Therefore, it is desired to improve the light emission efficiency in a light emitting device having a structure in which quantum dots made of a direct transition type III-V compound semiconductor are embedded in a group IV semiconductor buried layer.

For this reason, the present light emitting device includes a substrate containing Si and an active layer formed on the substrate, and the active layer is a quantum dot made of a direct transition type III-V group compound semiconductor material, and a surface of the quantum dot It is necessary to provide an outer shell portion that covers the whole and an IV group semiconductor embedded layer that embeds the quantum dots covered by the outer shell portion.
The present integrated element is provided with the above light emitting element and a functional element, and requires that the light emitting element and the functional element are integrated on the same substrate.

  Therefore, according to the present light emitting device and the present integrated device, the light emitting efficiency is improved in the light emitting device having the structure in which the quantum dots made of the direct transition type III-V compound semiconductor are embedded in the group IV semiconductor buried layer. There is an advantage that you can.

Hereinafter, the light emitting device and the integrated device according to the present embodiment will be described with reference to the drawings.
[First Embodiment]
First, a light-emitting element (semiconductor element; semiconductor light-emitting element) according to the first embodiment will be described with reference to FIGS.
The light emitting device according to the present embodiment is a quantum dot semiconductor light emitting device (quantum dot device) that can be formed on a Si (silicon) substrate. For example, as shown in FIG. And an active layer (light emitting layer) 2 formed thereon. Although the Si substrate 1 is used here, any substrate may be used as long as it is a substrate (a substrate containing Si) made of a Si-based material (that is, Si or a group IV semiconductor mixed crystal containing Si).

Here, the active layer 2 includes a quantum dot 5 made of a direct transition type III-V compound semiconductor material, a shell 6 that covers the entire surface of the quantum dot 5, and a group IV that embeds the quantum dot 5 covered by the shell 6. And a semiconductor buried layer 3.
The active layer 2 is also referred to as a quantum dot layer. A quantum dot (core; quantum dot core; central portion; core layer) 5 covered with a shell (outer shell portion; shell layer) 6 is referred to as a core-shell type quantum dot 4.

Here, the group IV semiconductor buried layer 3 is made of an indirect transition group IV semiconductor material, and here is a group IV semiconductor mixed crystal layer containing a Ge layer or Si.
In the present embodiment, the group IV semiconductor buried layer 3 is a layer made of Si _1-xy Ge _x C _y (0 ≦ x + y ≦ 1). From the viewpoint of ease of production, a SiGe layer or a SiGeC layer (a group IV semiconductor mixed crystal layer containing Si) is preferable. The IV group semiconductor buried layer 3 is formed of a material having a band gap energy larger than that of the core / shell type quantum dots 4. For this reason, it is also referred to as a barrier layer.

Further, the quantum dot 5 includes InAs _1-x Sb _x (0 ≦ x ≦ 1), In _1-x Ga _x As (0 ≦ x ≦ 1), InAs _1-x N (0 ≦ x ≦ 1), In _It is preferable to use any material (quantum dot material; core material) among _1-x Ga _x Sb (0 ≦ x ≦ 1) and InSb _1-x N _x (0 ≦ x ≦ 1).
The shell 6 is either In _x Ga _1-x As _y P _1-y (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) or Al _x Ga _y In _1-xy As (0 ≦ x + y ≦ 1). It is preferable to use a material (shell material; direct transition type III-V compound semiconductor material).

  In the present embodiment, the shell 6 is made of a direct transition type III-V compound semiconductor material capable of forming an energy barrier against both electrons and holes in the quantum dot 5, and the quantum dot 5, the shell 6, Constitutes a Type-1 type heterostructure (see FIG. 5). Thereby, electrons and holes (carriers) are confined inside the quantum dots 5, and the light emission efficiency (temperature characteristics of light emission efficiency) under a desired temperature condition can be improved.

Thus, in this embodiment, the band gap energy E _core of the quantum dots 5 is made smaller than the band gap energy E _shell of the shell 6. That is, the shell 6 is made of a direct transition type III-V group compound semiconductor material having a band gap energy larger than that of the quantum dots 5.
In particular, in order to realize a light-emitting element that can obtain good light emission efficiency in accordance with a desired temperature condition, the height of the energy barrier against electrons and holes in the quantum dot 5 (energy relative to the ground level of the quantum dot 5). The shell 6 may be made of a direct transition type III-V compound semiconductor material such that the height of the barrier (activation energy) becomes a desired height corresponding to a desired temperature condition. For example, in the case of the present embodiment, if the shell 6 is formed using a semiconductor material whose energy level of the direct transition conduction band is about 200 meV higher than the ground level of the quantum dots 5, the emission intensity even at room temperature (300K). It is possible to realize a light-emitting element having favorable temperature characteristics with little reduction in (luminous efficiency).

In this embodiment, the shell 6 is made of a direct transition type III-V compound semiconductor material in order to improve the temperature characteristics of luminous efficiency. However, the present invention is not limited to this. For example, the quantum dot 5 In order to reduce the group IV semiconductor impurity concentration and improve the light emission efficiency, the shell 6 may be made of an indirect transition type III-V compound semiconductor material.
Here, the thickness (film thickness) of the shell 6 may be one atomic layer or more. That is, by providing the shell 6 so that the group IV semiconductor buried layer 3 and the quantum dot 5 are isolated, the group IV semiconductor impurity concentration of the quantum dot 5 can be reduced, and the light emission efficiency can be improved. it can. However, considering the tunnel effect, the thickness is preferably 1 nm or more.

  On the other hand, in consideration of the diffusion length of the IV group semiconductor impurity into the quantum dot 5 as described later, the shell 6 reduces the diffusion length of the IV group semiconductor impurity into the quantum dot 5 to a desired length or less. It is preferable to have a thickness that allows the quantum dots 5 to have a desired group IV semiconductor impurity concentration. Thereby, the IV group semiconductor impurity density | concentration of the quantum dot 5 can fully be reduced, and it can be made to obtain favorable luminous efficiency. In the present embodiment, the thickness of the shell 6 is preferably 10 nm or more.

In the present embodiment, the thickness of the shell is preferably 20 nm or less so as not to become a resistance component during current injection.
Hereinafter, the principle by which the above-described operation / effect can be obtained by the light-emitting element including the core-shell type quantum dots 4 configured as described above will be described.
First, the principle that can reduce the group IV semiconductor impurity concentration of the quantum dots 5 will be described.

  Impurity diffusion can be expressed by the following equation (1), where C is an impurity atom concentration per unit volume, D is a diffusion coefficient, t is time, and x is distance.

  The diffusion length of group IV semiconductor impurities into the quantum dots 5 can be expressed by the following equation (2), where D is the diffusion coefficient and t is the time.

  In order for the III-V compound semiconductor quantum dots 5 to be stably present in the IV group semiconductor buried layer 3, the diffusion length of the IV group semiconductor impurities into the quantum dots 5 is such that the quantum dots 5 are crushed by impurities. It is considered that it is necessary to be about half of the quantum dot size. Since a general quantum dot size is small and about 20 nm, it is considered that the diffusion length needs to be within a range of about 10 nm.

Here, FIG. 2 shows an impurity concentration (normalized impurity concentration) distribution of a group III-V compound semiconductor quantum dot provided in the group IV semiconductor buried layer. In FIG. 2, the horizontal axis indicates the distance from the surface of the quantum dot.
As shown in FIG. 2, when the impurity concentration on the surface of the quantum dot is 100%, the impurity concentration is reduced to about 72% at a position of 5 nm from the surface of the quantum dot and is reduced to about 48% at a position of 10 nm. I understand that.

Therefore, in the core-shell type quantum dot 4 configured as described above, if the thickness of the shell 6 is about 5 nm, the impurity concentration on the surface of the quantum dot 5 can be reduced to about 72%, and if it is about 10 nm. The impurity concentration on the surface of the quantum dot 5 can be reduced to about 48%.
Thus, if the thickness of the shell 6 is 10 nm or more, the impurity concentration on the surface of the quantum dot 5 can be reduced to about 48%. Therefore, the diffusion length of the IV group semiconductor impurity is about half the quantum dot size ( It is possible to prevent the quantum dots 5 from being crushed by impurities and to obtain good light emission efficiency.

Next, the principle that can improve the temperature characteristics of the luminous efficiency will be described.
The temperature dependence of the luminous efficiency of the quantum dots is determined by the energy band structure of the conduction band that governs the quantum confinement of electrons, and can be expressed by the following equation (3). E _a is the activation energy, κ _B is the Boltzmann constant, T is the temperature, and C is a constant.

The activation energy E _a is the height of the barrier layer with respect to the ground level of the quantum dot, that is, the lowest band among the energy level of the ground level of the quantum dot and the energy level of the conduction band of the barrier layer. This corresponds to the energy difference between the energy levels.
Here, FIG. 3, the activation energy E _a is the emission intensity in the case of 50,100,150,200MeV (normalized emission intensity; Normalized intensity) shows the temperature dependence of the.

As shown in FIG. 3, as the activation energy E _a large room less decrease in emission intensity at (300K), it can be seen that no decrease luminous efficiency at room temperature. Emission intensity, when compared at room temperature, the activation energy E _a is in the case of 200 meV, the activation energy E _a is about 100 times in the case of 50 meV.
For example, when an InAs quantum dot (base size 30 nm, height 5 nm) is provided in the Si layer with a structure having no shell, the energy band structure is as shown in FIG.

In this case, the activation energy E _a is an energy difference between the energy level of the lowest Δ band in the energy level of the conduction band of the Si layer as the barrier layer and the energy level of the ground level of the InAs quantum dots. As shown in FIG. 4, this energy difference is almost 0 meV.
As described above, when a group III-V compound semiconductor quantum dot (here, InAs quantum dot) is embedded in the group IV semiconductor buried layer (here, Si layer), the energy level of the indirect transition conduction band of the group IV semiconductor buried layer. The energy level of the direct transition conduction band of the III-V compound semiconductor quantum dot (the energy level of the ground level of the quantum dot) is relatively low with respect to (the Δ band energy level of the conduction band of the group IV semiconductor buried layer). Close (energy level difference is small; here it is almost the same).

For this reason, carriers are not confined within the quantum dots, and the emission intensity decreases as the temperature approaches room temperature, and temperature characteristics with good emission efficiency cannot be obtained. In particular, little light is emitted at room temperature.
On the other hand, as in this embodiment, InAs is used for the quantum dots 5 and InP is used for the shells 6 in the IV group semiconductor buried layer (Si layer in this case) 3. It is made of a III-V compound semiconductor material capable of forming an energy barrier against both electrons and holes, and the quantum dots 5 and the shell 6 form a Type-1 type heterostructure (see FIG. 5). When the core-shell type quantum dot 4 is provided, the energy band structure is as shown in FIG.

In this case, the activation energy E _a is the lowest energy level in the conduction band of the InP shell 6 functioning as a barrier layer and the energy level of the ground level of the InAs core (InAs quantum dots) 5. The energy difference is about 200 meV as shown in FIG.
Thus, when the core-shell type quantum dot 4 using InAs for the quantum dot 5 and InP for the shell 6 is provided in the IV group semiconductor buried layer (here, Si layer) 3, the InAs quantum dot (III− The energy level of the direct transition conduction band of the group V compound semiconductor quantum dot) 5 (the energy level of the ground level of the quantum dot 5) of the direct transition conduction band of the InP shell (group III-V compound semiconductor shell) 6 The energy level (the energy level of the Γ band of the conduction band of the shell 6) is increased by about 200 meV, and the shell 6 substantially functions as a barrier layer for the quantum dots 5.

Thereby, the confinement of carriers inside the quantum dots 5 can be strengthened, the decrease in emission intensity can be reduced even at room temperature (300 K) (see FIG. 3), and the temperature characteristics of the emission efficiency can be improved. Good light emission (light emission efficiency) can be obtained regardless of the temperature.
Next, a method for manufacturing the light emitting device according to this embodiment will be described with reference to FIG.

Here, a core / shell type in which a quantum dot (III-V compound semiconductor quantum dot) 5 is InAs and a shell 6 is InP in a SiGeC layer (IV group embedded semiconductor layer) 3 on a Si substrate 1. A case where the quantum dots 4 are provided will be described as an example.
Crystal growth can be performed by metal organic chemical vapor deposition (MOVPE) or molecular beam epitaxy.

First, as shown in FIG. 6A, for example, after the Si (001) substrate 1 is heated to 650 ° C., disilane (Si ₂ H ₆ ), germane (GeH ₄ ), and monomethylsilane (SiH ₃ CH ₃ ) are added. Then, the SiGeC underlayer 3 </ b> A is grown on the Si (001) substrate 1.
Next, the state where the raw material supply is stopped is maintained while the temperature is constant, and the group IV raw material gas is sufficiently exhausted.

Next, as shown in FIG. 6A, the substrate temperature is lowered to 480 ° C. while supplying phosphine (PH ₃ ). Thereby, as shown in FIG. 6B, an adsorption layer 6X made of P is formed on the surface of the SiGeC underlayer 3A.
Then, as shown in FIG. 6 (b), after the temperature is stabilized, arsine (AsH ₃ ) and trimethylindium (TMIn) are supplied, and as shown in FIG. 6 (c), the core (here InAs quantum) is supplied. Dot) 5 is formed. Here, the InAs quantum dots 5 are formed on the InP underlayer 6A having a thickness of about one atomic layer (this constitutes a part of the shell 6).

Thereafter, PH ₃ and TMIn are supplied to form an InP cap layer 6B (which constitutes part of the shell 6) having a thickness of about one atomic layer as shown in FIG. 6 (d). As a result, the surface of the InAs quantum dots 5 is covered with the InP cap layer 6B. As a result, the InP shell 6 composed of the InP underlayer 6A and the InP cap layer 6B is formed.

Finally, as shown in FIG. 6D, Si ₂ H ₆ , GeH ₄ , and SiH ₃ CH ₃ are supplied, and as shown in FIG. 6E, the SiGeC cap layer is covered so that the entire surface is covered. Grow 3B. Thereby, the SiGeC buried layer 3 composed of the SiGeC underlayer 3A and the SiGeC cap layer 3B is formed. At this time, the P adsorption layer 6X formed in the region where the InAs quantum dots 5 are not formed disappears by diffusing or segregating on the surface side.

  In this way, as shown in FIG. 6 (e), core-shell type quantum dots 4 using InAs for the quantum dots 5 and InP for the shell 6 are formed in the SiGeC buried layer 3. In other words, on the Si (001) substrate 1, InAs is used for the quantum dots (III-V compound semiconductor quantum dots) 5 and InP is used for the shell 6 in the SiGeC buried layer (group IV semiconductor buried layer) 3. A light-emitting element having a structure in which the core-shell type quantum dots 4 are embedded is formed.

Here, the InP shell 6 (InP underlayer 6A) on the substrate side, that is, the lower side of the InAs quantum dots 5 is formed using the P adsorption layer 6X formed by supplying PH ₃ . For example, not only PH ₃ but also TMIn may be supplied to form an InP underlayer having a thickness of 2 atomic layers or more. In this case, the InP shell 6 (InP cap layer 6B) on the upper side of the InAs quantum dots 5 is also formed to have a thickness of 2 atomic layers or more, and the InP shell 6 having a thickness of 2 atomic layers or more is formed. May be.

Here, the SiGeC buried layer 3 is directly grown on the Si substrate 1. However, the present invention is not limited to this, and in order to improve the crystallinity of the SiGeC buried layer 3, for example, SiGeC or SiGe is used. A graded composition buffer layer or a Si buffer layer (for example, a low temperature Si buffer layer) may be inserted between the Si substrate 1 and the SiGeC buried layer 3.
Therefore, according to the light emitting device according to the present embodiment, the light emitting efficiency of the light emitting device having the structure in which the quantum dots 5 made of the direct transition type III-V compound semiconductor are embedded in the group IV semiconductor buried layer 3 is improved. There is an advantage that it can be improved.

  In other words, according to the present light emitting device, the core / shell type quantum dot structure is adopted, and the quantum dot 5 and the IV group semiconductor embedded layer 3 are isolated by the shell 6. Therefore, there is an advantage that the concentration of group IV semiconductor impurities inside the quantum dot 5 made of a direct transition type III-V compound semiconductor can be reduced, and the luminous efficiency can be improved.

  Further, according to the present light emitting device, a III-V group compound that adopts a core-shell type quantum dot structure and can form an energy barrier for both the electrons and holes in the quantum dots 5 in the shell 6. Since the quantum dots 5 and the shell 6 are made of a semiconductor material so as to form a Type-1 type heterostructure (see FIG. 5), carriers (in this case, electrons and electrons) to the quantum dots 5 are formed by the shell 6. There is an advantage that the quantum confinement effect of both holes) can be strengthened, and the light emission efficiency (temperature characteristic of light emission efficiency) can be improved under a desired temperature condition.

In particular, according to the present light emitting device, the structure (thickness and energy barrier height) of the shell 6 can be devised to be formed on the Si substrate 1, and the group III-V compound semiconductor quantum dots are embedded in the group IV semiconductor. It is possible to realize a quantum dot light emitting device that has a structure embedded with a buried layer, emits light with high efficiency, has low impurity concentration, and has good temperature characteristics.
In the above-described embodiment, the shell 6 is made of a III-V group compound semiconductor material that can form an energy barrier against both electrons and holes in the quantum dot 5, and the quantum dot 5, the shell 6, Constitutes a Type-1 type heterostructure (see FIG. 5), but is not limited to this, and the shell 6 can form an energy barrier against electrons or holes in the quantum dot 5. The quantum dot 5 and the shell 6 may be made of a III-V group compound semiconductor material so as to form a Type-2 type heterostructure. Also in this case, since it has a core-shell type quantum dot structure, the group IV semiconductor impurity concentration inside the group III-V compound semiconductor quantum dot 5 can be reduced, and the luminous efficiency can be improved. Moreover, since either an electron or a hole is confined in the quantum dot 5, the temperature characteristic of luminous efficiency can be improved. However, as in the above-described embodiment, the quantum dot 5 and the shell 6 form a Type-1 type heterostructure, and both electrons and holes are confined in the quantum dot 5 to emit light more. The temperature characteristic of efficiency can be improved.

In the above-described embodiment, the quantum dot layer is a single layer. However, the present invention is not limited to this. For example, a multilayer quantum dot layer may be provided. When providing a multilayer quantum dot layer, it is preferable to provide a spacer layer made of, for example, SiGeC or SiGe between the quantum dot layers.
[Second Embodiment]
Next, a light emitting device according to a second embodiment will be described with reference to FIG.

The light emitting device according to the present embodiment is a surface emitting laser (VCSEL; vertical cavity surface emitting laser) to which the present invention is applied. Vertical cavity surface emitting laser)
The surface-emitting laser is a Si-based surface-emitting laser (Si-based vertical cavity light-emitting element) that can be formed on a Si substrate. As shown in FIG. 7, the core-shell described in the first embodiment is used. IV semiconductor buried layer [here _{Si 1-xy Ge x C y} (0 ≦ x + y ≦ 1) buried layer] containing the type quantum dot 4 is a surface emitting laser using 3 as the active layer 2. In FIG. 7, the same components as those in the first embodiment described above (see FIG. 1) are denoted by the same reference numerals.

That is, as shown in FIG. 7, the surface emitting laser has a lower Si / SiO ₂ multilayer DBR mirror 11, a single-crystal Si layer 12, a p-type SiGeC layer (contact layer) on a Si substrate 10 in this order from the substrate side. ) 13, active layer (light emitting layer) 2, SiO ₂ insulating layer 14, n-type SiGeC layer (contact layer) 15, and upper Si / SiO ₂ multilayer DBR mirror 16. A p-side electrode 17 is formed of metal on the p-type SiGeC contact layer 13, and an n-side electrode 18 is formed of metal on the n-type SiGeC contact layer 15.

Here, the active layer 2, as in the first embodiment described above, IV group semiconductor buried layer in a 3 'wherein _{Si 1-xy Ge x C y} (0 ≦ x + y ≦ 1) embedded layer] The core-shell type quantum dot 4 is embedded. FIG. 7 shows a structure including two quantum dot layers.
SiO ₂ insulating layers 14 are formed on both sides of the active layer 2.

In addition, Si / SiO ₂ multilayer DBR mirrors 11 and 16 are provided so as to sandwich the active layer 2 from above and below, thereby forming a resonator structure.
Here, in the case of the DBR mirror having the simplest complete periodic structure, the maximum reflectance of the DBR mirror is obtained at a wavelength corresponding to four times the film thickness of each layer converted to the optical distance. That is, the film thickness of each layer is obtained as a thickness corresponding to 1/4 of the desired emission wavelength divided by the refractive index of each layer. Further, the maximum value of the reflectance can be increased by increasing the number of mirror periods.

Therefore, for example, in order to obtain a reflectance of 99% or more necessary for realizing a good VCSEL at a wavelength of 1.3 μm, the thickness of the Si film is 96 nm, and the thickness of the SiO ₂ film is 225 nm. The number of periods may be 4 or more.
The configuration of the DBR mirror (the material of each layer, the film thickness, the number of cycles, etc.) is not limited to the above-described one, and a multilayer DBR mirror configured by a combination of other known materials may be used. it can. For example, a conductive multilayer DBR mirror such as a SiGe / Si multilayer DBR mirror can be used. In this case, the p-side electrode 17 may be provided on the back side of the substrate.

Here, since the multilayer DBR mirrors are Si / SiO ₂ multilayer DBR mirrors 11 and 16 including an insulating film (SiO ₂ ), between the active layer 2 and the multilayer DBR mirrors 11 and 16, respectively, Contact layers (conductive semiconductor layers) 13 and 15 are provided. That is, the n-type SiGeC contact layer 15 extending to the outside of the upper multilayer DBR mirror 16 is provided between the active layer 2 and the upper Si / SiO ₂ multilayer DBR mirror 16. In addition, a p-type SiGeC contact layer 13 extending to the outside of the upper multilayer DBR mirror 16 and the n-type SiGeC contact layer 15 is provided between the active layer 2 and the lower Si / SiO ₂ multilayer DBR mirror 11. ing.

For this reason, the SiO ₂ insulating layer 14 is provided so as to be sandwiched between the p-type SiGeC contact layer 13 and the n-type SiGeC contact layer 15.
Note that the p-type SiGeC layer 13 may be a p-type SiGe layer. The n-type SiGeC layer 15 may be an n-type SiGe layer.
Next, a manufacturing method of the light emitting element (surface emitting laser) according to the present embodiment will be described with reference to FIG.

First, as shown in FIG. 8A, the Si film and the SiO ₂ film are alternately stacked on the Si substrate 10 by, for example, the CVD method to form the lower Si / SiO ₂ multilayer DBR mirror 11.
Next, as shown in FIG. 8A, another Si substrate 12A is wafer-bonded on the lower Si / SiO ₂ multilayer DBR mirror 11, and as shown in FIG. 8B, this Si substrate 12A. Is thinned by dicing and polishing. As a result, a single crystal Si layer 12 is formed on the lower Si / SiO ₂ multilayer DBR mirror 11 as shown in FIG.

Thereafter, as shown in FIG. 8D, on the single crystal Si layer 12, a p-type SiGeC layer (contact layer) 13, a group IV semiconductor buried layer [here, Si _1-xy Ge _{x Cy} (0 ≦ x + y ≦ 1) buried layer] The active layer 2 including the core-shell type quantum dots 4 and the n-type SiGeC layer (contact layer) 15A are formed in this order.
Crystal growth can be performed by metal organic chemical vapor deposition (MOVPE) or molecular beam epitaxy.

Specifically, first, as shown in FIG. 8D, a p-type SiGeC layer 13 doped with, for example, B (boron) as an impurity at 1 × 10 ¹⁸ cm ⁻³ is grown at a growth temperature of 650 ° C., for example. .
Next, an undoped SiGeC underlayer 3A [see FIG. 6A] is grown on the p-type SiGeC layer 13 to a thickness of 50 nm, for example, at a growth temperature of 650 ° C.

Next, the core-shell type quantum dots 4 are formed on the SiGeC underlayer 3A by the same method as in the first embodiment described above (see FIGS. 6B to 6D).
Next, an undoped SiGeC cap layer 3B [see FIG. 6 (e)] is grown to a thickness of 50 nm, for example, at a growth temperature of 480 ° C. so that the core-shell quantum dots 4 are embedded.

Thus, the core-shell type quantum dots 4 are included in the SiGeC buried layer (IV semiconductor buried layer) 3 composed of the SiGeC underlayer 3A and the SiGeC cap layer 3B on the p-type SiGeC layer 13. An active layer 2 is formed.
Next, as shown in FIG. 8D, an n-type SiGeC layer 15A doped with, for example, As (arsenic) as an impurity at 1 × 10 ¹⁸ cm ^{−3 is formed} on the active layer 2 at a growth temperature of 650 ° C., for example. Grow. Thereby, a part of the n-type SiGeC layer 15 is formed.

For example, for the growth of the SiGeC layer by the MOVPE method, for example, disilane (Si ₂ H ₆ ), germane (GeH ₄ ), or monomethylsilane (SiH ₃ CH ₃ ) may be used.
Thereafter, as shown in FIG. 8 (e), for example by lithography, SiO ₂ insulating as part of laminate structure p-type SiGeC layer 13 is etched (processed) in the mesa to expose the entire surface is covered Layer 14 is formed. Then, after planarizing the SiO ₂ insulating layer 14 by polishing so that the surface of the n-type SiGeC layer 15A is exposed, the entire surfaces of the n-type SiGeC layer 15A and the SiO ₂ insulating layer 14 exposed on the surface are covered. As shown in FIG. 8F, an n-type SiGeC layer 15B doped with 1 × 10 ¹⁸ cm ⁻³ of, for example, As (arsenic) as an impurity is grown at a growth temperature of 650 ° C., for example. Thereby, the n-type SiGeC layer 15 composed of the n-type SiGeC layer 15A and the n-type SiGeC layer 15B is formed. Instead of the remaining portion 15B of the n-type SiGeC layer 15, a conductive polycrystalline n-type Si layer may be formed.

Next, as shown in FIG. 8F, Si films and SiO ₂ films are alternately stacked on the n-type SiGeC layer 15 by, eg, CVD, and the upper Si / SiO ₂ multilayer DBR mirror 16 is formed. Form.
Thereafter, as shown in FIG. 8G, the n-side electrode formation region is etched until the n-type SiGeC layer 15 is exposed, for example, by lithography. Further, the p-side electrode formation region is etched until the p-type SiGeC layer 13 is exposed.

Then, an n-side electrode (metal electrode) 18 is formed on the surface of the n-type SiGeC layer 15 by, for example, a vacuum deposition method. Further, a p-side electrode (metal electrode) 17 is formed on the surface of the p-type SiGeC layer 13 by, for example, a vacuum deposition method.
In this manner, the IV group semiconductor buried layer including the core-shell type quantum dots 4 described in the first embodiment described above [here, Si _1-xy Ge _x C _y (0 ≦ x + y) is formed on the Si substrate 10. ≦ 1) Embedded Layer] A surface emitting laser using 3 as the active layer 2 is formed.

Therefore, according to the light emitting device (surface emitting laser) according to the present embodiment, the direct transition type III-V compound semiconductor is incorporated into the group IV semiconductor buried layer 3 as in the first embodiment described above. In the light emitting element having the structure in which the quantum dots 5 are embedded, there is an advantage that the light emission efficiency can be improved.
In other words, according to the present light emitting device, the core / shell type quantum dot structure is adopted, and the quantum dot 5 and the IV group semiconductor embedded layer 3 are isolated by the shell 6. Therefore, there is an advantage that the concentration of group IV semiconductor impurities inside the quantum dot 5 made of a direct transition type III-V compound semiconductor can be reduced, and the luminous efficiency can be improved.

  Further, according to the present light emitting device, a III-V group compound that adopts a core-shell type quantum dot structure and can form an energy barrier for both the electrons and holes in the quantum dots 5 in the shell 6. Since the quantum dots 5 and the shell 6 are made of a semiconductor material so as to form a Type-1 type heterostructure (see FIG. 5), carriers (in this case, electrons and electrons) to the quantum dots 5 are formed by the shell 6. There is an advantage that the quantum confinement effect of both holes) can be strengthened, and the light emission efficiency (temperature characteristic of the light emission efficiency) can be improved under a desired temperature condition.

In particular, according to the present light emitting device, the structure (thickness and energy barrier height) of the shell 6 can be devised to form on the Si substrate 1, and the III-V compound semiconductor quantum dots 5 can be formed into the IV group semiconductor. It is possible to realize a quantum dot light emitting device having a structure embedded by the embedded layer 3 and having a low impurity concentration, high efficiency, and good temperature characteristics.
In the above-described embodiment, the p-type SiGeC layer 13 and the p-side electrode 17 are provided on the substrate side. However, the present invention is not limited to this, and the n-type SiGeC layer and the n-side electrode are provided on the substrate side. May be.

Further, the structure of the surface emitting laser is not limited to the structure of the above-described embodiment, and the IV group semiconductor buried layer including the III-V compound semiconductor quantum dots is not limited to the structure of the other embodiments. The present invention can be applied to any surface emitting laser used as an active layer.
In this embodiment, the case where the present invention is applied to a surface emitting laser is described as an example. However, the present invention is not limited to this. For example, a light emitting diode (LED) or an LD (laser) is used. The present invention can also be applied to other light emitting elements such as diodes).
[Others]
In each of the above-described embodiments, the light-emitting element is described as a single light-emitting element. However, an integrated element may be configured by integrating the light-emitting elements of the above-described embodiments together with other functional elements on the same Si substrate. it can. In addition, although the board | substrate is used as the Si substrate, what is necessary is just the board | substrate (substrate containing Si) which consists of Si system material (namely, IV or a IV group semiconductor mixed crystal containing Si).

For example, as shown in FIG. 9, the integrated element is formed on a Si substrate 20 by a light emitting element (the light emitting element of the first embodiment described above or the surface emitting laser of the second embodiment described above) 21 and a light receiving element (functional element). ) 22 and an electronic circuit (electronic element; functional element) 23 may be integrated.
Here, the light receiving element 22 is configured by stacking, for example, a Si layer and a SiGeC layer (Si / SiGe light receiving element).

In the integrated element having such a configuration, the input light is converted from an optical signal to an electric signal by the light receiving element 22, subjected to various processes such as computation in the electronic circuit 23, and then the optical signal is output by the light emitting element 21. Will be output after being converted to.
Further, for example, as shown in FIG. 10, the integrated element is a driving element for driving the surface emitting laser on the same Si substrate 10 on which the surface emitting laser (light emitting element) of the second embodiment is formed. (Electronic element; functional element; for example, MOSFET; modulation drive circuit, electronic circuit) 30 may be integrated. In FIG. 10, the same components as those in the second embodiment described above (see FIG. 7) are denoted by the same reference numerals.

Specifically, as shown in FIG. 10, a p-type MOSFET 30 is monolithically integrated on the same Si substrate 10 on which the surface emitting laser (light emitting element) of the second embodiment described above is formed. Can also be configured.
Such an integrated device can be manufactured as follows, for example.
After growing an n-type Si layer 31 on the single crystal Si layer 12, a p ⁺ region (p ⁺ -Si layer) 32 is formed by ion implantation. Thereafter, a SiO ₂ film 33 is laminated, a gate electrode 34 is formed thereon, and a source electrode 35 and a drain electrode 36 are formed in contact with the p ⁺ -Si layer 32. At this time, the drain electrode 36 may be configured as a common electrode with one p-side electrode of the surface emitting laser. Thereby, the p-type MOSFET 30 constituting the modulation driving circuit of the surface emitting laser is formed.

Note that the configurations of the integrated elements are not limited to these configurations, and the light emitting elements of the first and second embodiments described above can be applied to the light emitting element portions of the integrated elements having other configurations.
Further, the present invention is not limited to the configurations described in the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention.

It is a typical sectional view showing the composition of the light emitting element concerning a 1st embodiment of the present invention. It is a figure which shows the impurity concentration distribution of the III-V group compound semiconductor quantum dot provided in the IV group semiconductor embedding layer. It is a figure which shows the temperature dependence of the emitted light intensity in case activation energy is 50, 100, 150, 200 meV. It is a figure which shows the energy band structure at the time of providing InAs quantum dot in Si layer. It is a figure which shows the energy band structure of the light emitting element (what provided the core-shell type quantum dot which consists of InAs core and InP shell in Si layer) concerning 1st Embodiment of this invention. (A)-(e) demonstrates the manufacturing method of the light emitting element (what provided the core-shell type quantum dot which consists of an InAs core and an InP shell in the SiGeC layer) concerning 1st Embodiment of this invention. It is a typical sectional view for this. It is a typical sectional view showing the composition of the light emitting element (surface emitting laser which used the SiGeC layer containing the core shell type quantum dot which consists of an InAs core and an InP shell as an active layer) concerning a 2nd embodiment of the present invention. (A)-(g) is typical sectional drawing for demonstrating the manufacturing method of the light emitting element (surface emitting laser) concerning 2nd Embodiment of this invention. It is a schematic diagram which shows the structural example of an integrated element provided with the light emitting element concerning each embodiment of this invention. It is typical sectional drawing which shows the other structural example of an integrated element provided with the light emitting element (surface emitting laser) concerning 2nd Embodiment of this invention.

Explanation of symbols

1 Si substrate 2 Active layer (light emitting layer)
3 Group IV semiconductor buried layer [Si _1-xy Ge _{x Cy} (0 ≦ x + y ≦ 1) layer; SiGeC buried layer]
3A SiGeC underlayer 3B SiGeC cap layer 4 Core-shell type quantum dot 5 III-V compound semiconductor quantum dot (core)
6 shell 6A InP underlayer 6B InP cap layer 6X adsorption layer 10 Si substrate 11 lower Si / SiO ₂ multilayer DBR mirror 12 single crystal Si layer 12A Si substrate 13 p-type SiGeC layer (contact layer)
14 SiO ₂ insulating layer 15, 15A, 15B n-type SiGeC layer (contact layer)
16 Upper Si / SiO ₂ multilayer DBR mirror 17 p-side electrode 18 n-side electrode 20 Si substrate 21 light emitting element 22 light receiving element 23 electronic circuit (electronic element)
30 Drive element (electronic element; p-type MOSFET; modulation drive circuit, electronic circuit)
31 n-type Si layer 32 p ⁺ -Si layer 33 SiO ₂ film 34 gate electrode 35 source electrode 36 drain electrode

Claims (10)

A substrate containing Si;
An active layer formed on the substrate,
The active layer includes a quantum dot made of a direct transition type III-V group compound semiconductor material, an outer shell portion that covers the entire surface of the quantum dot, and an IV group semiconductor that embeds the quantum dot covered by the outer shell portion. A light emitting element comprising: an embedded layer.   The light emitting device according to claim 1, wherein the outer shell is made of a semiconductor material that can form an energy barrier against electrons or holes in the quantum dots.   The said outer shell part has thickness which can make the diffusion length of the IV group semiconductor impurity into the inside of the said quantum dot below a desired length, It is characterized by the above-mentioned. Light emitting element.   The light emitting device according to claim 1, further comprising a multilayer DBR mirror provided so as to sandwich the active layer vertically. 5. The light emitting device according to claim 1, wherein the group IV semiconductor buried layer is made of Si _1-xy Ge _{x Cy} (0 ≦ x + y ≦ 1). The core comprises InAs _1-x Sb _x (0 ≦ x ≦ 1), In _1-x Ga _x As (0 ≦ x ≦ 1), InAs _1-x N (0 ≦ x ≦ 1), In _1-x 6. The material according to claim 1, wherein the material is made of any one of Ga _x Sb (0 ≦ x ≦ 1) and InSb _1-x N _x (0 ≦ x ≦ 1). The light emitting element of description.   The light emitting device according to claim 1, wherein the outer shell portion is made of a III-V group compound semiconductor material. The outer shell portion is made of In _x Ga _1-x As _y P _1-y (0 ≦ x ≦ 1, 0 ≦ y ≦ 1) or Al _x Ga _y In _1-xy As (0 ≦ x + y ≦ 1). The light-emitting element according to claim 1, wherein   The light emitting device according to claim 1, wherein the outer shell has a thickness of 10 nm to 20 nm. The light emitting device according to any one of claims 1 to 9,
With functional elements,
An integrated element, wherein the light emitting element and the functional element are integrated on the same substrate.

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