JP3464890B2 - Semiconductor light emitting device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light emitting device, and more particularly to a semiconductor light emitting device having a multilayer structure of a nitride containing a group III element such as Ga.

[0002]

2. Description of the Related Art Conventionally, GaN-based semiconductor light emitting devices have been developed in various places as semiconductor lasers in the wavelength range from blue to ultraviolet since the formation of a p-type layer by adding Mg was successful. However, although a slight amount of laser emission was obtained, many problems to be solved still remain before commercialization.

One of the main problems is that the threshold current and operating voltage of laser emission are large. The reason is that a good ohmic contact cannot be obtained even if the metal having the largest work function is used for the current electrode.

In order to improve the characteristics of ohmic contact, it is necessary to increase the carrier density of the contact layer made of n-type and p-type GaN, which is the base of the current electrode, but GaN crystal is particularly used as a p-type impurity. It is a big problem that the activation rate of Mg ions is low and that the hole density obtained is three orders of magnitude lower than that of the added Mg. At present, the low activation rate of Mg ions in GaN-based semiconductors is generally considered to be an inherent limit of GaN-based crystals, and attempts to improve this have not yet been successful.

It is argued that if hydrogen mixed in from the carrier gas is removed at the same time as Mg is added, a p-type layer having a high hole density can be obtained, but in reality, if the hydrogen concentration in the carrier gas is reduced, Mg It is known that the activation rate of ions is further reduced.

There is a report suggesting that the characteristics of ohmic contact can be improved by depositing several kinds of nitride films such as ScN on the p-type GaN layer (see Nobuaki Teraguchi, JP-A-8-32115). . However, it has not been confirmed experimentally yet.

While GaN-based semiconductor light emitting devices have been attracting attention as light sources from blue to ultraviolet, manufacturing a long wavelength semiconductor light emitting device using a nitride-based material has also become an important issue. . If this succeeds, GaAs or Ga
Without mixing light emitting devices of different materials such as P,
There is an advantage of forming a multi-color display device only with a GaN-based material.

However, the luminous efficiency of the GaN-based light emitting device is
It tends to be significantly reduced on the long wavelength side. One of the reasons is that if the In composition of the nitride, which helps to increase the wavelength, is increased, I
n ball-up (unreacted I on the surface of the growth layer
(Phenomenon of discharging n) occurs, and metal In is precipitated in the crystal, so that a high-quality crystal cannot be grown. In addition, as the In composition increases, the mismatch of the lattice constant between the adjacent GaN-based crystal layers increases, and many defects such as dislocation lines and cracks occur in the growth layer due to lattice distortion.

Although such a problem can be avoided to some extent by improving the method of controlling the temperature during crystal growth, a good long wavelength semiconductor light emitting device using a nitride containing In is still obtained. The current situation is that it has not been done.

In order to obtain a long-lived semiconductor laser device, it is extremely important to form the reflecting surface of the optical cavity having a smooth mirror surface. However, a GaN-based material tends to have a wurtzite type crystal structure, and a crystal having this structure has a very hard property, so that it is difficult to obtain a good cleavage plane. Here, the cleavage plane refers to a fracture surface of a single crystal formed along a crystal plane having a large interplanar spacing and a weak bonding force.

Further, there is a large lattice mismatch with sapphire used as a growth substrate, which makes it difficult to obtain a good mirror surface when cleaving the GaN-based growth layer together with the sapphire substrate. When using a sapphire substrate, the substrate surface (11 bar 0
0) An inclination angle of 3 degrees with respect to the crystal plane is provided and polishing is performed, and a GaN-based crystal is grown on the surface. For this reason, if the sapphire substrate is made extremely thin to facilitate cleavage, the sapphire cross section will be a flat cleavage surface, but the Ga grown on it will grow.
The cross section of the multilayer structure of the N-based laser is not flat.

Compared to sapphire, the value of the lattice constant is GaN.
It is possible to use SiC close to
In fact, since SiC is a harder material than sapphire,
Cleavability is further reduced.

Here, a conventional GaN-based semiconductor light emitting device,
In order to clarify the structural correspondence with the semiconductor light emitting device of the present invention in the long wavelength region, GaN conventionally developed has been developed.
The structure of the semiconductor-based semiconductor light emitting device and the problems in increasing the wavelength of the semiconductor light emitting device will be described in more detail with reference to the drawings.

InGaN superlattice (hereinafter MQW; Multi)
GaN with an active layer (abbreviated as Quantum Well)
FIG. 14 shows a sectional structure of the semiconductor light emitting device. The main part of this semiconductor light emitting device is the InGaN MQW active layer 28.
And n-type and p-type GaN (hereinafter n-GaN, p-GaN
Abbreviated as “) and light guide layers 5 and 7, and n-AlG
It is composed of aN and p-AlGaN cladding layers 4 and 8. The clad layers 4 and 8 are made of AlGaN having a large forbidden band width and contribute to confine light and carriers in order to enhance the efficiency of laser emission. In the following description, the suffix indicating the composition of the layer containing a ternary or higher element is omitted unless otherwise necessary.

This semiconductor light emitting device has an n type on the lower side,
It is continuously formed on the sapphire substrate 27. GaN
Layers 2 and 9 are Al / Pt / Au electrode 3 and Pt / Au electrode 1
1 is a contact layer that forms a base. Current constriction is SiO
_{2 The} film 10 is used.

In the structure of another semiconductor light emitting device shown in FIG. 15, the current confinement is performed by the n-GaN layer 29 forming an internal stripe of the opposite conductivity type to the p-GaN contact layer 9.

Further, in FIG. 15, if the carrier density of the n-GaN current confinement layer 29 forming the internal stripe is increased, or if a material having a smaller forbidden band width than that of the active layer can be used, absorption of laser light can be achieved. As a result, the transverse mode of the laser light is controlled, and a light beam having a stable circular cross section can be obtained. However, one of the problems is that the conventional GaN-based crystal has a low activation rate of impurity ions, so that even if the internal stripe structure shown in FIG. 15 is used, the advantage cannot be sufficiently obtained. Here, the lateral mode refers to a mode that determines the spread of the light beam propagating in the longitudinal direction through the active layer and the guide layer in the lateral direction.

The conventional GaN-based semiconductor light-emitting devices shown in FIGS. 14 and 15 are both formed on a sapphire substrate 27, and the crystal system of the GaN-based multilayer structure forming the laser is wurtzite type. A single crystal of SiC may be used as the growth substrate. In order to obtain light emission in the long wavelength region, a nitride having a large In composition and a small band gap must be used as the active layer as described above. FIG. 16 shows the problem that occurs in the GaN-based crystal at this time.

FIG. 16 is a diagram showing the relationship between the band gap and the lattice constant of InN, GaN, and AlN. The solid and broken lines in the upper part of the figure represent the ternary compounds Ga _x Al _1-x N, In _y Ga.
_The changes in the lattice constant and the change in the forbidden band width when the values of the compositions x, y, and z in _1-y N and In _z Al _1-z N are changed from 0 to 1 are shown. The broken line at the bottom of the figure is the effective lattice constant of the (0001) plane of the sapphire substrate that is lattice-matched with the GaN-based crystal.

To obtain long-wavelength light emission from this figure,
It can be seen that it is essential to bring the composition closer to the InN side. On the broken line of In _z Al _1-z N (0 ≦ z ≦ 1), the lattice mismatch with the sapphire substrate increases in proportion to z, so In _y Ga _1-y N (0 ≦ y ≦ 1) It is understood that it is most advantageous to select the optimum value of y in the range where lattice matching with the sapphire substrate is possible, on the solid line.

If the composition of In is increased, cracks will occur due to excessive strain in the growth layer, so the thickness of the growth layer must be made extremely small. In addition, as described above, In
In order to avoid these, the value of the In composition of the active layer of the GaN-based semiconductor laser must be limited to 20% or less of the In composition as shown by the arrow in FIG.

In the case of a light emitting diode, it is possible to further increase the value of In composition and obtain light emission close to yellow, but it is also known that the light emission efficiency decreases exponentially with wavelength. .

[0023]

As described above, since it is difficult to obtain high-concentration p-type and n-type layers in the conventional GaN-based semiconductor light-emitting device, it is possible to obtain a current electrode having excellent ohmic characteristics. However, there is a drawback that the operating voltage becomes excessive. Also in the internal stripe type structure, it is difficult to control the transverse mode of laser light by providing an absorption region having a high carrier density in the vicinity of the active layer and obtain a laser beam having a stable circular cross section.

Further, in the GaN-based semiconductor light emitting device in the long wavelength region, there is a problem that it is extremely difficult to grow a material containing a large amount of In having a low emission efficiency and a small forbidden band width. In addition, when forming a GaN-based semiconductor laser on a sapphire substrate, the GaN-based material has a wurtzite crystal structure, which makes cleavage difficult and it is difficult to obtain a good reflective surface necessary for laser operation. There was a problem that was.

The present invention has been made to solve the above-mentioned problems, and by using a novel nitride semiconductor material capable of emitting light in a long wavelength region with high efficiency, p-type which has been conventionally insufficient. The activation rate of impurity ions is improved, the voltage drop at the current electrode is reduced, the luminous efficiency is improved, and the transverse mode control of laser light is enabled by the internal stripe structure. It is an object of the present invention to provide a semiconductor light emitting device having a long life and excellent productivity, in which the lattice matching between the object semiconductor material and the substrate is improved to improve the cleavage, and a good reflecting surface can be easily obtained.

[0026]

In a semiconductor light emitting device of the present invention, a nitride containing Sc is used as a material, and Sc is added to a GaN-based crystal to improve the activation rate of p-type impurity ions such as Mg. Is characterized by.

Further, by performing the crystal growth on the NaCl type single crystal substrate, the growth of the GaN type crystal containing Sc also having the NaCl type crystal structure is promoted, the lattice matching with the substrate is excellent, and the forbidden band width is small. Moreover, it is characterized in forming a semiconductor light emitting device having good cleavage. In this way, it is possible to obtain a long-lived semiconductor light emitting device that operates with high luminous efficiency in a long wavelength region, which was impossible with conventional GaN-based materials.

Specifically, in the semiconductor light emitting device of the present invention, at least one of the layers constituting the multilayer structure of the semiconductor light emitting device has at least Sc, Y and a lanthanide, an actinide element, Zr, Hf, V, Nb and Ta. It is characterized by including any one of.

Preferably, the above-mentioned at least Sc, Y and lanthanide, actinide element, Zr, Hf, V, Nb
And a layer containing any one of Ta are p-type.

Preferably, at least the above Sc, Y and lanthanide, actinide element, Zr, Hf, V,
The layer containing any one of Nb and Ta further contains oxygen.

It is also preferable that one of the layers having the above-mentioned multilayer structure is used.
_{Thing, In x Sc y Ga z Al} w N (x + y + z + w
= 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, 0 ≦ w ≦
A layer having the composition of 1) is included.

One of the layers forming the multilayer structure is I
_{n x Sc y Ga z Al w} N (x + y + z + w = 1,0 ≦
x ≦ 1, 0 ≦ y <0.6, 0 ≦ z ≦ 1, 0 ≦ w ≦ 1), and the layer having the above composition has a zinc blende type crystal structure. It is characterized in that it is formed adjacent to the layer.

The semiconductor light emitting device of the present invention has a multilayer structure _{In x Sc y Ga z Al w} N (x + y + z + w = 1,
0 ≦ x ≦ 1, 0.6 ≦ y ≦ 1, 0 ≦ z ≦ 1, 0 ≦ w ≦
It is characterized in that it is composed of a layer having any one of the values in the composition range of 1), and its growth substrate is a single crystal substrate having a NaCl type crystal structure.

Preferably, the single crystal substrate having the NaCl type crystal structure is made of MgO.
The semiconductor light-emitting device of the present invention, any of the compositions of at least the active layer and the current confinement layer, In _x Sc _y Ga _z A
l _w N (x + y + z + w = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦
1, 0 ≦ z ≦ 1, 0 ≦ w ≦ 1).

The active layer of the semiconductor light emitting device of the present invention has a superlattice structure, and the barrier layer of the superlattice structure is In _x G 2.
_{a 1-x N (0 ≦} x ≦ 0.2), the well layer is Sc _y Ga
_1-yN (0.3 ≦ y ≦ 1).
Preferably, the barrier layer having the superlattice structure is Sc _y1 Ga.
_1-y1 N, and the well layer is made of Sc _y2 Ga _1-y2 N (y2> y1).

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a cross-sectional structure of a long-wavelength GaN-based semiconductor light emitting device containing Sc according to the first embodiment of the present invention. The semiconductor light emitting device of the present invention shown in FIG. 1 includes an n-Si substrate 1 and ScGaN / InGaN.
It is characterized in that it has an MQW active layer 6. ScGaN
Increases the composition of Sc, the band gap decreases. The composition of the other multilayer structures is the same as in FIG.

The Si substrate 1 in FIG. 1 is a Si single crystal having low conductivity and containing no impurities. Therefore, FIG.
Similar to the sapphire substrate 27 of 4, the lower Al / Pt /
The Au current electrode 3 is formed on the upper surface of the n-GaN contact layer 2.

FIGS. 2 and 3 show a first embodiment in which a multilayer structure of a semiconductor laser is formed from the n-type side and the p-type side using the low-resistance n-Si substrate 1a and p-Si substrate 12 as epitaxial substrates, respectively. It is a modification of a form. By using the Si substrate having high conductivity as described above, the lower electrode can be directly taken out from the lower portion of the Si substrate. At this time, n-Si
A good ohmic electrode can be obtained by using the Al / Pt / Au electrode 3 for the substrate and the Pt / Au electrode 11 for p-Si.

ScGaN / InGa with reference to FIGS. 4 and 5.
Detailed structure of N. MQW active layer 6 and Si substrates 1, 1
The reason for using a and 12 will be described. As shown in FIG. 4, the active layer 6 is made of In _x Ga _1-x N (0 ≦ x ≦
0.2) barrier layer and Sc _y Ga _1-y N (0.3 ≦ y
≦ 1) has an MQW structure in which well layers are alternately stacked, and the light guide layers 5 and 7 adjacent to the upper and lower sides are similarly formed by In _x Ga _1-x N (0 ≦ x ≦ 0.2). It is formed. By using the MQW active layer having this composition range,
It is possible to obtain light emission in a wide wavelength range from blue to red.

When the composition of Sc is in the range of y <0.6, Sc _y
The crystal structure of Ga _1-y N is zinc blende type. If Sc _y Ga _1-y N is zinc blende type even if the composition of Sc is y> 0.6, and if it is lattice-matched with other zinc blende type GaN-based crystals, its lattice The matching state is much inferior to the case where the In-based material in the corresponding wavelength region is used.

If the composition of Sc is y> 0.6, Sc _y
The crystal structure of the Ga _1-y N layer changes to the NaCl type. Figure 5
As shown in, the NaCl-type ScN and the zinc blende-type Ga
It is perfectly lattice-matched with N. Therefore, N of y> 0.6
The lattice matching state of the aCl-type Sc _y Ga _1-y N with the zinc blende type crystal is more stable than the lattice matching state of the zinc blende types with y <0.6.

From this, it is understood that the lattice matching state of ScGaN in the NaCl type is more rigorously established and the strain is relaxed. Further, the NaCl type crystal has strong ionicity and has an action of stabilizing a rather unstable zinc blende type GaN type crystal.

Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 6 shows the structure of the MQW active layer according to the second embodiment of the present invention. Different from FIG. 4, the barrier layer of the MQW active layer, the well layer, and the waveguide layers vertically adjacent to the active layer are all made of ScGaN. The composition of Sc is such that the barrier layer and the waveguide layer are Sc _y1 Ga _{1 -y1.}
N, when the well layer is Sc _y2 Ga _{1 -y2} N, y2> y
Make sure 1 holds.

As is apparent from the description of the first embodiment, in the above case, the MQW active layer can be divided into three different types depending on the composition of Sc. That is, firstly Sc
When the composition is small, the MQW active layer is entirely composed of zinc blende type crystals. If the Sc composition of the well layer is increased,
The l-type well layer is embedded in a zinc blende type matrix, and if the Sc composition is further increased, the MQW active layer is entirely composed of NaCl type crystals. Which of these forms is selected is determined by the required emission wavelength.

If the multilayer structure constituting the semiconductor light emitting device is made up of all NaCl type layers having a large Sc composition, the substrate material can be NaCl type single crystal accordingly. Table 1 shows the crystal structures and lattice constants of the substrate materials that can be used for the multilayer structure having a large Sc composition. The lattice constant of ScN is 4.22A. The substrate is not limited to the NaCl type, and a zinc blende type (indicated as ZB in Table 1) may be used as long as lattice matching is established.

[0046]

[Table 1]

G containing Sc according to the second embodiment of the present invention
FIG. 7 shows a sectional structure of an aN-based semiconductor laser. This Sc
GaN-based semiconductor lasers containing Mg have an internal stripe structure using NaCl-type MgO as a substrate, and all the multilayer structures constituting the laser are Sc _y Ga _1-y N (y> 0.
It is characterized in that it is composed of the NaCl type layer of 6).

That is, the GaN-based semiconductor laser including Sc of the second embodiment is Sc _0.7 Ga _0.3 N / Sc.
_0.85 Ga _0.15 N MQW active layer 18, adjacent optical guide layers 17 and 19 of n-Sc _0.7 Ga _0.3 N and p-Sc _0.7 Ga _0.3 N, and adjacent n-A
l _0.2 Sc _0.6 Ga _0.2 N and p-Al _0.2 Sc _0.6 G
a _0.2 N cladding layers 16 and 20, and n-Sc _0.6 Ga _0.4 N and p-Sc _0.6 G adjacent to the cladding layers 16 and 20.
a _0.4 N contact layers 15 and 21 and p-Al on top
Clad layer 20 made of _0.2 Sc _0.6 Ga _0.2 N and p
An internal stripe type current constriction made of n-ScN formed between the -Sc _0.6 Ga _0.4 N contact layer 21 and the junction surface between the upper cladding layer and the contact layer so as to narrow the junction surface from both sides. Composed of layer 22.

These multi-layered structures are formed by epitaxial growth on the insulating NaCl type MgO substrate 14. On the upper and lower contact layers 15 and 21, current electrodes 3 made of Al / Pt / Au and Pt / Au, respectively,
11 is formed.

The semiconductor laser of the second embodiment is
The substrate, including the substrate, is composed entirely of NaCl type crystals. N
Since the aCl type crystal is composed of an ionic bond, it has a better cleavage property than a rigid substrate composed of a covalent bond such as sapphire or SiC, and a reflective surface forming a laser cavity can be formed very easily. Since a perfect mirror-like cleaved surface is obtained in this way, it is possible to avoid the loss of laser light from the reflecting surface and improve the laser gain.

As a modification of the second embodiment, FIG. 8 shows a sectional structure of a GaN-based semiconductor light emitting device containing Sc grown from the p-type side on an insulating MgO substrate 14. At this time, the buried current constriction layer becomes the p-ScN layer 24. The other configuration is similar to that of FIG. 7, and thus the description is omitted.

As described above with reference to FIG. 15, the buried current confinement layer has the effect of enhancing the efficiency of laser emission by supplying carriers intensively to the laser active layer, and the current confinement layer serves as a light absorber. The cross-sectional shape of the light beam is made circular by using the transverse mode control to stabilize the light beam.

In order for the embedded current constriction layer to act as a light absorber, its forbidden band width must be reduced or its carrier concentration must be increased. In the conventional GaN-based semiconductor laser that does not contain Sc as shown in FIG. 15, the forbidden band width of the GaN-embedded current confinement layer 29 is larger than the effective forbidden band width of the active layer 28, and this is set to a high carrier concentration. Was difficult. Therefore, in the conventional GaN-based semiconductor laser device, it was not possible to obtain a stable light beam having a circular cross section that is practically important and having low noise.

However, by adding Sc to the GaN-based crystal, the forbidden band width can be made sufficiently smaller than the forbidden band width of the active layer, and the carrier activation rate with respect to the impurity addition amount is significantly increased. Easily, 5 × 10 ¹⁸ cm ^-3
The carrier density can be about the same. As described above, in the GaN-based semiconductor laser including Sc shown in FIGS. 7 and 8, the embedded current confinement layer formed of the n-ScN layer 22 and the p-ScN layer 24 is provided with the lateral mode control function of the laser light. It was possible to obtain a stable and highly practical light beam having a small signal-to-noise ratio and a circular cross section.

In the GaN-based semiconductor laser containing Sc shown in FIGS. 7 and 8, n-Sc _0.6 Ga _0.4 N and p-S are used.
Since the carrier density of the c _0.6 Ga _0.4 N contact layers 15 and 21 can be easily increased by adding Sc, the Al / Pt / Au electrode 3 and the Pt / Au electrode 13 are formed.
It goes without saying that the ohmic characteristics between and are significantly improved and a low operating voltage can be obtained.

Here, taking Mg which is a p-type impurity as an example,
The reason why the activation rate of impurity ions is increased by adding Sc to a GaN-based crystal will be described. As mentioned above, by adding Mg to the GaN crystal,
Although it can be a p-type, only a p-type crystal having a low hole density can be obtained because the activation rate of Mg ions is low. It is considered that the reason is that Mg and H (hydrogen) form a complex in a GaN-based crystal and reduce the activation rate of Mg ions.

This phenomenon cannot be solved by performing a heat treatment after adding Mg or by adding Mg in a gas atmosphere having a low H partial pressure to grow a crystal. In the present invention, Sc is added at the same time when Mg is added to the GaN-based crystal.
It has been found for the first time that the addition rate of Mg as the composition significantly improves the activation rate of Mg ions.

When Sc is added to the GaN-based crystal as a composition, the composite of Mg and H contained in the crystal is separated by the fact that Sc occupies the lattice point, and H penetrates into the interstitial lattice and is inactivated. On the other hand, it is considered that the separated Mg will occupy other lattice points and become Mg ions that supply holes. By adding Sc as a composition, the conventional 3
The hole density of the GaN-based crystal, which was limited to × 10 ¹⁷ cm ^-3, could be increased to 5 × 10 ¹⁸ cm ^-3 . In order to obtain good results as described above, it was necessary to precisely control the addition of Sc and Mg to ensure sufficient uniformity.

The above-mentioned action was observed not only in Sc but also in Y and lanthanide, actinide element, Zr, Hf, V, Nb and Ta, or a mixture thereof. Also, a low resistance p-type can be obtained by mixing a small amount of oxygen together with the above metal. It should be noted that the effect of increasing the activation rate of not only p-type impurities but also n-type impurity ions was observed by adding these elements as a composition.

Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 9 is a diagram showing a cross-sectional structure of a GaN-based laser containing Sc according to the third embodiment. This GaN-based semiconductor laser containing Sc is formed on a conductive p-MgO substrate, and Pt /
The Au current electrode 11 is taken out from the lower portion of the p-MgO substrate, and the p-ScN embedded current confinement layer 24.
The lower the allowed to remain partially n-Sc _0.6 Ga _0.4 N layer 15a, selects buried ridge (hereinafter SBR to form an n-Sc _0.6 Ga _0.4 N contact layer 15 again thereon; Sele
This is different from FIG. 8 in that it has a current confinement layer 24 made of p-ScN having a ctively Buried Ridge structure.

Since a Mg-type substrate can obtain a p-type crystal having a high conductivity, a G-containing Sc layer is formed on the MgO substrate from the p-type side.
By forming the aN-based multilayer structure, it is possible to manufacture a highly productive laser in which the current electrode is taken out from the lower portion of the p-MgO substrate 23. The n-Sc _0.6 Ga _0.4 N layer 1 is formed below the p-ScN embedded current confinement layer 24.
By adopting the SBR structure in which 5a is partially left, the interface characteristics between both are improved and the recombination rate of holes is reduced, so that a highly efficient semiconductor laser can be obtained.

FIG. 10 shows p-S in the SBR structure.
The growth of the cN current constriction layer 24 and the final n-Sc _0.6 Ga _0.4 N contact layer 15 is omitted, and n-Al _0.2 Sc _0.6 is omitted.
Ga _0.2 N n-Sc so as to leave a part of the clad layer 16
_0.6 Ga _0.4 N layer 15a and n-Al _0.2 Sc _0.6 G
a _0.2 N ridge-type S that is mesa processed with the cladding layer 16
It is a cGaN semiconductor laser. Al / Pt / A on top
The u electrode 3 is formed on the n-Sc _0.6 Ga _0.4 N layer 15a as a contact layer.

G containing mesa ridge type Sc shown in FIG.
The aN semiconductor laser has much higher productivity than that of FIG. 9 because the epitaxial process for forming the SBR structure of FIG. 9 is greatly simplified.

Next, a fourth embodiment of the present invention will be described with reference to FIG. The GaN-based internal stripe semiconductor laser including Sc in FIG. 11 is the GaN described in FIG.
ScGaN / compared to the internal stripe semiconductor laser
Having an InGaN MQW active layer, n-ScGa
The difference is that it has an N-current constriction layer and that a multilayer structure is formed on a Si substrate.

Since the Si substrate used here has a low conductivity without adding impurities, the lower Al / Pt / Au substrate is used.
The electrode 3 has a structure that is taken out from the upper portion of the lower n-GaN contact layer 2.

As described above, if a GaN-based semiconductor layer containing no Sc is grown on a Si substrate, a zinc blende type crystal is obtained. Therefore, as shown in FIG. 11, n-Ga
N contact layer 2, n-AlGaN cladding layer 4, n-
When the InGaN guide layer 5 is grown, a zinc blende type layer is grown.

When stacking the ScGaN / InGaN MQW active layer 6 on the zinc blende type n-InGaN guide layer 5, if the composition is Sc _y Ga _1-y N (0.3 <y <0.
In the range of 6), a zinc blende type ScGaN layer grows, and in the range of Sc _y Ga _1-y N (0.6 <y <1), a NaCl type ScGaN layer grows.

At this time, the InGaN layer forming the MQW can be lattice-matched as a zinc blende type in any case as shown in FIG.
P-InGaN on N / InGaN MQW active layer 6
Guide layer 7, p-AlGaN cladding layer 8, p-GaN
Up to the contact layer 9, all GaN-based crystals not containing Sc grow as zinc blende type. The n-ScGaN current confinement layer 25 is a zinc blende type when the Sc composition is 0.6 or less, and a NaCl type when the Sc composition is 0.6 or more.

As a result, the multilayer structure shown in FIG. 11 is all zinc blende type if the Sc composition is 0.6 or less. 6
If it is above, only the layer containing Sc becomes NaCl type, and this is the structure embedded in the GaN-based zinc blende type crystal layer not containing Sc.

The GaN-based semiconductor laser containing Sc shown in FIG. 11 has S only in the MQW active layer 6 and the current confinement layer 25.
Although it does not contain c, this structure enables a semiconductor laser whose wavelength range is expanded to the long wavelength side, and a stable laser beam with a circular cross section can be obtained. The benefits can be realized.

As a modification of the fourth embodiment, a conductive n-Si substrate is used to take out an Al / Pt / Au electrode from the lower part thereof to improve productivity, and a conductive p-type electrode is used.
The fact that the Pt / Au electrode can be grown from the p-type side using the —Si substrate and taken out from the lower portion of the n-Si substrate is the same as in the description of FIGS. 1 to 3.

Next, the fifth aspect of the present invention will be described with reference to FIGS.
The embodiment will be described. In FIG. 12, a conductive n-Si substrate is used as compared with the fourth embodiment, and the Al electrode 26 is taken out from the lower part of the substrate.
11 except that it has the SBR structure described in
It is similar to the GaN-based semiconductor laser including See also FIG.
Is similar to the GaN-based laser including Sc in FIG. 12 except that the current confinement has the mesa ridge structure described in FIG. Each of these semiconductor lasers has the advantages described in the related section.

In FIGS. 12 and 13, a conductive p-Si substrate is used instead of the n-Si substrate, and the Pt / Au electrode 11 is formed on the lower side of the substrate by growing from the p-type side.
It is possible to obtain a GaN-based semiconductor laser that contains Sc having.

The present invention is not limited to the above embodiment. In the above embodiments, the case where all the active layers containing Sc have the MQW structure has been described, but the active layer may be a single layer containing Sc.
Although all semiconductor lasers have been described, they can be used as a light emitting diode or a light receiving diode if they are simplified or slightly modified, for example, by omitting the guide layer. Further, the characteristics of the GaN-based semiconductor layer containing Sc of the present invention can be used not only for the light emitting device but also for manufacturing a transistor or the like. Other various modifications can be made without departing from the scope of the present invention.

[0075]

As described above, according to the present invention, by using the MQW structure made of GaN containing Sc in the active layer, a semiconductor light emitting device in a long wavelength region, which has been impossible in the conventional InGaN MQW active layer, is provided. Obtainable. Further, by adding Sc to the GaN contact layer, the activation rate of impurity ions, in particular, p-type impurity ions such as Mg is increased as compared with the prior art, and a GaN semiconductor laser having a low resistance ohmic electrode and a low operating voltage is provided. Can be manufactured.

In the conventional internal stripe type GaN-based semiconductor laser, it was difficult to control the transverse mode because the carrier density of the GaN current confinement layer could not be increased. However, by using GaN containing Sc as the current confinement layer, By making the forbidden band width of the current constriction layer smaller than that of the active layer and increasing the carrier density thereof, it is possible to obtain a stable laser beam having a circular cross section and less noise.

In addition, NaCl type MgO or Si
As a substrate, a GaN-based multilayer structure containing NaCl-type or zinc-blende-type Sc is formed. Can be formed,
The reflection loss of laser light can be reduced.

In this way, it is possible to obtain a long-life semiconductor light-emitting device that operates with high luminous efficiency in a long-wavelength region, which was not possible with conventional GaN-based materials. In addition, similar effects are obtained for Y and lanthanide, actinide element, Z
This can be achieved by adding r, Hf, V, Nb and Ta to the GaN-based multilayer structure, and mixing a small amount of oxygen with the above metals.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a semiconductor light emitting device including Sc according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view of a semiconductor light emitting device showing a modification of the first embodiment of the present invention.

FIG. 3 is a sectional view of a semiconductor light emitting device showing another modification of the first embodiment of the present invention.

FIG. 4 is an MQW including Sc according to the first embodiment of this invention.
Sectional drawing which shows the detail of a structure.

FIG. 5 is a diagram showing the compatibility between zinc blende type GaN and NaCl type ScN.

FIG. 6 is an MQW including Sc according to the second embodiment of this invention.
Sectional drawing which shows the detail of a structure.

FIG. 7 is a sectional view of a semiconductor light emitting device including Sc according to a second embodiment of the present invention.

FIG. 8 is a sectional view of a semiconductor light emitting device showing a modified example of the second embodiment of the present invention.

FIG. 9 is a sectional view of a semiconductor light emitting device including Sc according to a third embodiment of the present invention.

FIG. 10 is a cross-sectional view of a semiconductor light emitting device showing a modification of the third embodiment of the present invention.

FIG. 11 is a sectional view of a semiconductor light emitting device including Sc according to a fourth embodiment of the present invention.

FIG. 12 is a sectional view of a semiconductor light emitting device including Sc according to a fifth embodiment of the present invention.

FIG. 13 is a sectional view of a semiconductor light emitting device showing a modification of the fifth embodiment of the present invention.

FIG. 14 is a sectional view of a conventional striped GaN-based semiconductor light emitting device.

FIG. 15 is a sectional view of a conventional internal stripe type GaN-based semiconductor light emitting device.

FIG. 16 is a diagram showing a relationship between a forbidden band width of InN, GaN, and AlN and a lattice constant.

[Explanation of symbols]

1 ... Si substrate 1a ... n-Si substrate 2 ... n-GaN contact layer 3 ... Al / Pt / Au electrode 4 ... n-AlGaN cladding layer 5 ... n-InGaN guide layer 6 ... ScGaN / InGaN.MQW active layer 7 ... p-InGaN guide layer 8 ... p-AlGaN cladding layer 9 ... p-GaN contact layer 10 ... SiO ₂ film 11 ... Pt / Au electrode 12 ... p-Si substrate 14 ... MgO substrate _{15 ... n-Sc 0.6 Ga 0.4} n Contacts layer _{15a ... n-Sc 0.6 Ga 0.4} n layer _{16 ... n-Al 0.2 Sc 0.6} Ga 0.2 n clad layer _{17 ... n-Sc 0.7 Ga 0.3} n guiding layer _{18 ... Sc 0.7 Ga 0.3 n /} Sc 0.85 Ga 0.15 n · MQ
W active layer _{19 ... p-Sc 0.7 Ga 0.3} N guiding layer _{20 ... p-Al 0.2 Sc 0.6} Ga 0.2 N cladding layer _{21 ... p-Sc 0.6 Ga 0.4} N contact layer 22 ... n-ScN current confinement layer 24 ... p- ScN current constriction layer 25 ... n-ScGaN current confinement layer 26 ... Al electrode 27 ... Sapphire substrate 28 ... InGaN.MQW active layer 29 ... n-GaN current confinement layer

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A-8-32115 (JP, A) JP-A-8-293624 (JP, A) JP-A-8-274370 (JP, A) JP-A-8- 306958 (JP, A) JP 8-148718 (JP, A) JP 5-82447 (JP, A) JP 63-184324 (JP, A) JP 10-256601 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01S 5/00-5/50 H01L 33/00

Claims (5)

(57) [Claims] 1. A semiconductor light emitting device having a multilayer structure of a nitride formed on a substrate, wherein an active layer included in the multilayer structure has a well layer of Sc _y G 2.
a _1-y N (0.3 ≦ y ≦ 1), the barrier layer is In _x Ga _1-x
A semiconductor light emitting device comprising a superlattice layer of N (0 ≦ x ≦ 0.2) . 2. A semiconductor light emitting device having a multilayer structure of a nitride formed on a substrate, wherein an active layer included in the multilayer structure has a well layer of Sc _y G
a _1-y N (0.3 ≦ y ≦ 1), the barrier layer is Sc _y1 Ga
A semiconductor light-emitting device comprising a _1-y1 N (y> y1) superlattice layer . In the semiconductor light-emitting device comprising a multilayer structure wherein a nitride formed on the substrate, an active layer included in the multilayer structure, In _x Sc _y Ga _z A
l _w N (x + y + z + w = 1, 0 ≦ x ≦ 1, 0.3 ≦ y ≦
1, 0 ≦ z ≦ 1, 0 ≦ w ≦ 1)
A semiconductor light-emitting device comprising a layer . 4. An In _x Sc _y layer other than the active layer.
Ga _z Al _w N (x + y + z + w = 1, 0 ≦ x ≦ 1, 0.
6 ≦ y ≦ 1, 0 ≦ z ≦ 1, 0 ≦ w ≦ 1)
4. A layer according to claim 1, which further comprises a layer having
The semiconductor light emitting device according to any one of the above. 5. The well layer is Sc _y Ga _1-y N (0.3
≤ y ≤ 1) part of Sc is Y, lanthanoid, activator
Less of the elemental elements Zr, Hf, V, Nb and Ta
Substituted with at least one species, or
2. The semiconductor light emitting device according to item 2.