JP3449619B2 - Semiconductor light emitting device - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a semiconductor light emitting device. More specifically, the present invention relates to a semiconductor light emitting device capable of emitting light with high brightness by lowering an operating voltage.

A semiconductor light emitting element is a light emitting diode (hereinafter referred to as LED) having a double heterojunction such as a pn junction or a pin, a super luminescent diode (SLD) or a semiconductor laser diode (hereinafter referred to as a semiconductor laser diode).
A semiconductor element that generates light, such as LD).

[0003]

2. Description of the Related Art Conventionally, a blue LED has a smaller brightness than red and green and has a difficulty in practical use, but in recent years, a gallium nitride compound semiconductor is used and a low resistance p-type semiconductor layer using Mg as a dopant is used. As a result, the brightness is improved and it is in the limelight.

Here, a gallium nitride compound semiconductor is a compound of a group III element Ga and a group V element N or
A semiconductor made of a compound in which a part of Ga of the group III element is replaced with another group III element such as Al and In and / or a part of N of the group V element is replaced with another group V element such as P and As. Say.

An LED using a conventional gallium nitride-based compound semiconductor is manufactured as follows, and FIG. 4 is a perspective view of a completed LED chip of the gallium nitride-based compound semiconductor.

First, a substrate 21 made of sapphire (Al ₂ O ₃ single crystal) or the like is used at a low temperature of 400 to 700 ° C. at a low temperature of 400 to 700 ° C. with a carrier gas H ₂ together with a carrier gas H ₂ by an organometallic compound vapor phase growth method (hereinafter referred to as MOCVD method). Trimethylgallium (hereinafter referred to as TMG) which is a gas, ammonia (NH ₃ ) and SiH ₄ as a dopant are supplied to form a low temperature buffer layer 22 composed of an n-type GaN layer in a thickness of about 0.01 to 0.2 μm. , Then 700-12
The same gas is supplied at a high temperature of 00 ° C, and n-type Ga of the same composition is supplied.
The high temperature buffer layer 23 made of N is formed in a thickness of about 2 to 5 μm.

Then, a raw material gas of trimethylaluminum (hereinafter referred to as TMA) is further added to the reaction gas in the reaction tube, and n-type Al _z G containing Si as an n-type dopant is added.
a _{1- z} N (0 <z ≦ 1) layer is formed, and n-type cladding layer 2 is formed.
4 is formed to have a thickness of about 0.1 to 0.3 μm.

Next, a material having a bandgap energy smaller than that of the clad layer, for example, trimethylindium (hereinafter, T
MI) is introduced and In _y Ga _1-y N (0 ≦ y ≦
The active layer 25 composed of 1) is formed to a thickness of about 0.05 to 0.1 μm.

Further, with the same source gas as the gas used for forming the n-type cladding layer 24, the impurity source gas was replaced with SiH ₄ , and Mg or Zn as a p-type impurity was replaced with biscyclopentadienyl magnesium (hereinafter referred to as Cp ₂ (Mg)
Alternatively, it is added as dimethyl zinc (hereinafter referred to as DMZn) and introduced into the reaction tube to form the p-type clad layer 26 of p-type A.
The l _z Ga _1-z N layer is vapor-grown. Here, the reaction gas is supplied so that the Al composition ratio z becomes the same value as z of the n-type cladding layer 24 for ease of manufacturing. These n
The type clad layer 24, the active layer 25, and the p-type clad layer 26 form a double heterojunction.

Then, to form the cap layer 27, Cp ₂ Mg or DMZn is supplied as an impurity source gas with the same source gas as that for the buffer layer 23 to grow a p-type GaN layer to a thickness of about 0.3 to 2 μm.

After that, a protective film is provided and heat treatment for annealing the p-type layer or electron beam irradiation is performed to activate the p-type cladding layer 26 and the cap layer 27.

Next, after removing the protective film, a resist is applied and patterned to form an n-side electrode, and a part of each grown semiconductor layer is removed by etching to form an n-type clad layer. 24 or the buffer layer 23 is exposed.

Then, a metal film of Au, Al or the like is formed by, for example, vapor deposition, sputtering or the like to form both the p-side and n-side electrodes 29, 30, respectively.
An LED chip is formed by dicing.

[0014]

Among the conventional gallium nitride based compound semiconductors, the double heterojunction semiconductor light emitting device has high luminous efficiency but high operating voltage. Further, if a material having a small band gap energy, that is, a material having a small Al composition ratio z of Al _z Ga _{1 -z} N is used for the n-type cladding layer and the p-type cladding layer in order to lower the operating voltage, the operating voltage becomes low. However, there is a problem in that the outflow of electrons from the active layer to the p-type clad layer increases and the luminous efficiency decreases.

It is an object of the present invention to solve the above problems and to provide a semiconductor light emitting device having a double hetero structure, in which the light emitting efficiency does not decrease and the operating voltage is low.

[0016]

A semiconductor light emitting device of the present invention
Is an n-type clad layer made of n-type AlGaN and a p-type A
InGaN with a p-type cladding layer made of lGaN
Has a sandwich structure with an active layerThe p
While keeping the Al ratio of the mold clad layer constantThe n-type
By reducing the Al ratio of the rud layer, the band of the active layer is reduced.
Of the p-type clad layer determined by the gap energy
Band of the n-type cladding layer is set to half or less of Al ratio
The gap energy is defined as the band gap energy of the active layer.
The difference with the energyThe aboveBand gap of p-type cladding layer
Energy and bandgap energy of the active layer
Of the difference1/3 ~1 /2 andCharacterized by being configured to
And The second semiconductor light emitting device according to the present invention is described in claim 1.
In the mounted semiconductor light emitting device, the n-type cladding layer is
It is connected to the n-side electrode and has Ga between it and the n-side electrode.
The buffer layer made of N is intervened.
To collect. Third Double Heterojunction Semiconductor of the Present Invention
The light emitting element is the semiconductor light emitting element according to claim 1,
n-type clad layer made of n-type AlGaN and p-type AlG
With a p-type cladding layer made of aN, made of InGaN
It has a sandwich structure sandwiching the active layer,The p-type
While keeping the Al ratio of the rud layer constantThe n-type crack
The band ratio of the active layer is reduced by reducing the Al ratio of the active layer.
Al of the p-type clad layer determined by the up energy
The ratio of the band gap of the n-type clad layer is less than half of the ratio.
Up energy to the bandgap energy of the active layer.
The difference with GeeThe aboveBand gap energy of p-type cladding layer
Difference between the ruggie and the bandgap energy of the active layer
of1/3 ~1 /2 andTo beWesthand,The n-type cladding
From a layerInjection of electrons into the active layer, The n-type cladding
The bandgap energy of the p-type cladding layer
Compared to the case of equalizing the band gap energy
In addition to making it possible to operate at low voltage, the effective mass of holes is
Utilizing the fact that it is larger than the effective mass of the childPositive holes
Effectively confined in the valence band of the conductive layer,From the active layer
It is possible to prevent holes from leaking into the n-type cladding layer.
It is characterized in that the reactive current is not increased.
It A fourth semiconductor light emitting device according to the present invention is defined in claim 3.
In the semiconductor light emitting device, the n-type cladding layer is on the n-side.
It is connected to the electrode and is GaN between it and the n-side electrode.
It is characterized in that a buffer layer consisting of
To do. The fifth double heterojunction type light emitting diode of the present invention
Is the substrate and n-type GaN provided on the substrate.
And a n provided on the buffer layer.
N-type clad layer made of AlGaN
An active layer made of InGaN provided on the head layer,
A p-type layer made of p-type AlGaN provided on the active layer.
And a rudd layer,The Al ratio of the p-type clad layer is set equal to
Keep it constantThe Al ratio of the n-type cladding layer is reduced.
And the band gap energy of the active layer.
The total Al ratio of the p-type cladding layer is half or less, and
The band gap energy of the n-type cladding layer is
The difference from the bandgap energy of the active layerThe abovep type
The band gap energy of the rud layer and the band gap energy of the active layer.
Of the gap energy1/3 ~1 /2 andBecome
Like thisFrom the n-type cladding layerElectricity to the active layer
Child injectionBand gap energy of the n-type cladding layer
Is the bandgap energy of the p-type cladding layer
Compared to the caseIt can be done at low voltage
And the effective mass of holes is larger than the effective mass of electrons.
Take advantage ofEffective holes in the valence band of the active layer
Trapped inPositive from the active layer to the n-type cladding layer
Increases reactive current by preventing hole leakage
The feature is that it is not. Sixth semiconductor of the present invention
The body laser includes a substrate and an n-type Ga provided on the substrate.
A buffer layer formed of an N layer and provided on the GaN layer
Ruan n-type clad layer made of n-type AlGaN, and the n-type
Provided on the cladding layerRuInGaN active layer
And p-type AlGaN provided on the active layer
Provided on the p-type clad layer and the p-type clad layer
and a cap layer made of p-type GaN,The p-type club
While keeping the Al ratio of the dead layer constantThe n-type cladding
The band gap of the active layer is reduced by reducing the Al ratio of the layer.
The Al ratio determined by the
The bandgap energy of the pad layer is compared with the bandgap energy of the active layer.
And the gap energyThe abovep-type cladding layer
Band gap energy and band gap of the active layer.
The difference between1/3 ~1 /2 andTo beWest
The injection of electrons into the active layerThe n-type cladding layer
Band gap energy of the p-type cladding layer
Band gap energy compared toLow
In addition to the voltage, the effective mass of holes is
Utilizing the fact that it is larger than the effective mass ofHoles said activity
Effectively confined within the valence band of the layer,From the active layer
to prevent holes from leaking into the n-type cladding layer
It is characterized in that the reactive current is not increased.
It A seventh semiconductor laser according to the present invention is described in claim 6.
In the semiconductor laser, the substrate is a sapphire substrate.
It is characterized by Eighth semiconductor light emitting device of the present invention
Is an n-type clad layer made of n-type AlGaN and a p-type A
With a p-type cladding layer made of lGaN,
Has a sandwich structure sandwiching an active layer,Hole in front
Effectively confined in the valence band of the active layer,Active layer
To prevent leakage of holes into the n-type cladding layer.
To the extent possible, the bandgap of the n-type cladding layer
The energy is lowered so that electrons are injected into the active layer.,Previous
The bandgap energy of the n-type cladding layer is set to p
Equal to the bandgap energy of the clad layer
Compared to the caseThe n-type crack is used so that it can be performed at a low voltage.
The Al ratio of the layerThe Al ratio of the p-type clad layer is set equal to
Keep it constantBand gap energy of the active layer
To increase the reactive current.
It is characterized by doing so. Ninth semiconductor of the present invention
The light emitting element is the semiconductor light emitting element according to claim 8,
The n-type cladding layer is connected to the n-side electrode,
A buffer layer made of GaN should be interposed between the n-side electrode and
It is characterized by being tightened. The tenth half of the invention
The conductor light emitting element is the semiconductor light emitting element according to claim 1.
And an n-type clad layer made of n-type AlGaN and a p-type A
With a p-type cladding layer made of lGaN,
Has a sandwich structure sandwiching an active layer,The p-type
While keeping the Al ratio of the clad layer constantThe n-type club
The Al ratio of the active layer is reduced to reduce the bandgap of the active layer.
In order to obtain a value determined by the cap energy, the n
Lower the bandgap energy of the mold cladding layer,
From the n-type cladding layerInjection of electrons into the active layerBut,
The bandgap energy of the n-type cladding layer is
equal to the bandgap energy of the p-type cladding layer
If Compared toIt can be done at low voltage and
Utilizing that effective mass of hole is larger than effective mass of electron
do itEffectively confine holes in the valence band of the active layer,
The abovePrevents leakage of holes from the active layer to the n-type cladding layer
To prevent the reactive current from increasing.
It is characterized by that. Eleventh semiconductor light emitting device of the present invention
Is the semiconductor light emitting device according to claim 10,
The mold clad layer is connected to the n-side electrode,
A buffer layer made of GaN is interposed between the electrodes.
It is characterized by being. The twelfth semiconductor laser of the present invention
The laser includes an n-type clad layer made of n-type AlGaN and p-type
InGaN with p-type cladding layer made of AlGaN
It has a sandwich structure with an active layer consisting ofThe above
While keeping the Al ratio of the p-type cladding layer constantN-type
By reducing the Al ratio of the clad layer, the band of the active layer is reduced.
The Al ratio is determined by the gap energy,
Lower the bandgap energy of the n-type cladding layer
hand, From the n-type cladding layerInjection of electrons into the active layer
But, The bandgap energy of the n-type cladding layer
Equal to the bandgap energy of the p-type cladding layer
Compared with the caseIf it can be done at low voltage,
In addition, the effective mass of holes is larger than the effective mass of electrons.
UsingEffectively close holes within the valence band of the active layer
Put the aboveLeakage of holes from the active layer to the n-type cladding layer
To prevent this from increasing the reactive current.
Sea lion andThe aboveThickness of active layerToLaser oscillation is possible
DegreeToIt is characterized by Thirteenth semiconductor of the present invention
The body laser is the semiconductor laser according to claim 12,
The sandwich structure is provided on the substrate and
At least between the sandwich structure and the substrate
A buffer layer made of GaN is provided. Of the present invention
The fourteenth semiconductor laser according to claim 12 or 13.
In a semiconductor laser, the sandwich structure is on a substrate
And a substrate having the sandwich structure.
Gap made of at least GaN on the surface side opposite to
It is characterized in that a layer is provided. Fifteenth of the present invention
The semiconductor laser according to claim 14 is the semiconductor laser according to claim 14.
The cap layer and the sandwich structure.
The part is etched into a mesa shapeCharacterized by
AndThe sixteenth semiconductor light emitting device of the present invention is an n-type Al
The InGaN layer is separated from the GaN layer and the p-type AlGaN layer.
It has a sandal sandwich structure,Of the p-type cladding layer
While keeping the Al ratio constantA of the n-type AlGaN layer
1 ratio to reduce the band gap of the InGaN layer.
Al of the p-type AlGaN layer determined by the
The ratio of the n-type AlGaN layer is less than half the ratio.
Band gap of the InGaN layer.
The difference betweenThe aboveBandi of p-type AlGaN layer
-Up energy and band gap of the InGaN layer
Difference of energy1/3 ~1 /2 andConfigured to be
It is characterized by that. Seventeenth semiconductor light emitting device of the present invention
The semiconductor light emitting device according to claim 16, wherein
The AlGaN layer is connected to the n-side electrode,
A buffer layer made of GaN is interposed between the side electrode and
It is characterized by being. 18th semiconductor of the present invention
The light emitting device includes an n-type AlGaN layer and a p-type AlGaN layer.
Then, it has a sandwich structure sandwiching the InGaN layer,
While keeping the Al ratio of the p-type AlGaN layer constantPrevious
The Al ratio of the n-type AlGaN layer is reduced so that the In
The above is determined by the band gap energy of the GaN layer
The Al ratio of the p-type AlGaN layer is half or less, and the n-type is
The band gap energy of the AlGaN layer is
The difference from the band gap energy of the GaN layerThe abovep type
Band gap energy of AlGaN layer and InG
of the difference from the bandgap energy of the aN layer1/3 ~1
/2 andTo beWesthand,From the n-type AlGaN layerThe above
Injection of electrons into the InGaN layerThe n-type AlGaN layer
Band gap energy of the p-type AlGaN layer
Compared to the case of equalizing the band gap energy
In addition to making it possible to operate at low voltage, the effective mass of holes is
Utilizing the fact that it is larger than the effective mass of the childPositive holes
Effectively confined in the valence band of the conductive layer,InGaN layer
Can prevent holes from leaking from the n-type AlGaN layer to the n-type AlGaN layer.
In order to prevent the reactive current from increasing.
A nineteenth semiconductor light emitting device according to the present invention is characterized by:
18. The semiconductor light emitting device according to 18, wherein the n-type AlGa
The N layer is connected to the n-side electrode and is connected to the n-side electrode.
A buffer layer made of GaN is interposed between
It is characterized by 20th semiconductor diode of the present invention
From the n-type GaN layer provided on the substrate and the substrate
And an n-type buffer layer formed on the n-type buffer layer.
And an n-type AlGaN layer formed on the n-type AlGaN layer.
And an InGaN layer formed on the InGaN layer.
And a p-type AlGaN layer,The p-type AlGaN layer
While keeping the Al ratio ofOf the n-type AlGaN layer
The band ratio of the InGaN layer is reduced by reducing the Al ratio.
A of the p-type AlGaN layer determined by the up energy
The band of the n-type AlGaN layer is set to half or less of the 1 ratio.
The gap energy is determined by the band gap of the InGaN layer.
The difference with the energyThe aboveBand of p-type AlGaN layer
Gap energy and band gap of the InGaN layer
The difference between1/3 ~1 /2 andTo beWest
hand,From the n-type AlGaN layerElectric power to the InGaN layer
Child injection, The band gap of the n-type AlGaN layer
The bandgap energy of the p-type AlGaN layer
Compared to making it equal to RugeyCan be done at low voltage
And the effective mass of holes is
Take advantage of the bigHoles are valence electrons of the InGaN layer
Effectively confined in the obi,From the InGaN layer to the n-type
By making it possible to prevent holes from leaking to the AlGaN layer,
The feature is that the reactive current is not increased.
A twenty-first semiconductor laser of the present invention is a substrate and a substrate
A buffer layer made of n-type GaN provided in the
Provided on the layerRun-type AlGaN layer and the n-type
Provided on the AlGaN layerRuInGaN layer and the In
A p-type AlGaN layer provided on a GaN layer, and the p-type
Provided on the AlGaN layerRuA cap made of p-type GaN
Has a layerConstant Al ratio in the p-type AlGaN layer
Kept atThe Al ratio of the n-type AlGaN layer is reduced.
The band gap energy of the InGaN layer.
The n-type AlGaN layer van
The gap energy of the InGaN layer
The difference from the cap energyThe abovep-type AlGaN layer van
Gap energy and the band gap of the InGaN layer.
Of energy difference1/3 ~1 /2 andTo beWest
Injecting electrons into the InGaN layer, The n-type Al
The band gap energy of the GaN layer is set to the p-type AlG
When the band gap energy of the aN layer is made equal to
Compared toEnables low voltage and effective hole
Utilizing the fact that the mass is larger than the effective mass of the electronHole
Effectively confined within the valence band of the InGaN layer,
RecordLeakage of holes from the InGaN layer to the n-type AlGaN layer
To prevent this from increasing the reactive current.
Characterized by the fact thatItThe 22nd semiconductor according to the present invention
22. The semiconductor laser according to claim 21, wherein the laser is
The substrate is a sapphire substrate. The present invention
The twenty-third semiconductor light emitting device of
Type AlGaN layer and InGaN layer sandwiched
Has a chi structure,Holes in the valence band of the InGaN layer
Effectively trapped,From the InGaN layer to the n-type AlG
To the extent that holes can be prevented from leaking to the aN layer,
The band gap energy of the n-type AlGaN layer is low.
The injection of electrons into the InGaN layer., The n-type
The band gap energy of the AlGaN layer is set to the p-type A
If the bandgap energy of the lGaN layer is made equal
Compared withThe n-type AlGa so that it can be performed at a low voltage
The Al ratio of the N layer isThe Al ratio of the p-type AlGaN layer is
Stay constantBand gap of the InGaN layer
Increase the reactive current by decreasing the value determined by the energy.
The feature is that it is not made big. Second of the present invention
24. The semiconductor light emitting device according to claim 4, wherein
In the child, the n-type AlGaN layer is connected to the n-side electrode
And a bag made of GaN between the n-side electrode and
It is characterized in that the fiber layer is interposed. Starting
The twenty-fifth semiconductor light emitting device of the present invention comprises an n-type AlGaN layer,
Sandwich sandwiching InGaN layer with p-type AlGaN layer
Has a switch structure,The Al ratio of the p-type AlGaN layer is set equal to
Keep it on your bodyReduce the Al ratio of the n-type AlGaN layer
The band gap energy of the InGaN layer
Of the n-type AlGaN layer to obtain a value determined by
Lower the bandgap energy,The n-type AlG
From aN layerInjection of electrons into the InGaN layer, N
The band gap energy of the AlGaN layer of the p-type
It was made equal to the band gap energy of the AlGaN layer.
Compared to the caseIt is possible to operate at a low voltage and holes
Taking advantage of the fact that the effective mass of is larger than the effective mass of electron
handThe holes are effectively confined within the valence band of the active layer,
RecordLeakage of holes from the InGaN layer to the n-type AlGaN layer
To prevent this from increasing the reactive current.
Characterized by the fact that The twenty sixth semiconductor invention of the present invention
The optical element is the semiconductor light emitting element according to claim 25,
The n-type AlGaN layer is connected to the n-side electrode,
A buffer layer made of GaN is interposed between the n-side electrode and
It is characterized by being condemned. 27th of the present invention
The semiconductor light emitting device is the semiconductor light emitting device according to claim 1.
In addition, the n-type AlGaN layer and the p-type AlGaN layer are
It has a sandwich structure sandwiching a GaN layer,The p-type
While keeping the Al ratio of the AlGaN layer constantThe n-type A
The Al ratio of the lGaN layer is reduced to reduce the InGaN layer.
Al ratio determined by the band gap energy of
And the bandgap energy of the n-type AlGaN layer
LowerFrom the n-type AlGaN layerInGaN
Electron injection into the layerBandwidth of the n-type AlGaN layer
The gap energy of the p-type AlGaN layer
Compared to the case whereRow at low voltage
And the effective mass of holes is the effective quality of electrons.
Taking advantage of being greater than quantityPositive holes in the active layer
Effectively confined in the baby band,From the InGaN layer to the n
To prevent holes from leaking into the AlGaN layer.
To prevent the reactive current from increasing, andThe aboveInG
Thickness of aN layerToThe extent to which laser oscillation is possibleTothing
Is characterized by. A twenty-eighth semiconductor laser of the present invention is a claim.
Item 28. The semiconductor laser according to Item 27,
The structure is provided on the substrate and the sandwich structure is
Between the structure and the substrate, a bar made of at least GaN.
Is provided with aIs characterized by. Of the present invention
The 29th semiconductor laser according to claim 27.
In a semiconductor laser, the sandwich structure is on a substrate
And a substrate having the sandwich structure.
Cap made of at least GaN on the surface side opposite to
Layers are providedIIt is characterized by 30th of the present invention
31. The semiconductor light emitting device according to claim 29.
In the cap layer and the sandwich structure
Part of is etched into a mesa shapeIThat
Characterize.

The n-type cladding layer is n-type Al _x G.
a _1-x N (0 ≦ x ≦ 0.5), and the active layer is
In _y Ga _1-y N (0 ≦ y ≦ 1), and the p-type
Whether the clad layer is p-type Al _z Ga _1-z N (0 <z ≦ 1)
It is preferable that 2x ≦ z.

Further, by providing a buffer layer made of GaN between one of the cladding layers and the substrate,
It is preferable because the strain of the clad layer can be relaxed, the generation of crystal defects and dislocations in the clad layer can be prevented, and the resistance of the semiconductor layer can be reduced.

According to the semiconductor light emitting device of the present invention, since the n-type cladding layer is made of a material having a bandgap energy smaller than that of the p-type cladding layer, electrons are injected from the n-type cladding layer into the active layer at a low voltage. Easily done. On the other hand, since the p-type clad layer is made of a material having a large bandgap energy as in the conventional case, the escape of electrons from the active layer to the p-type clad layer is small, and the recombination of electrons and holes in the active layer is suppressed. Contribute. Further, since holes have a larger effective mass than electrons, even if the bandgap energy of the n-type clad layer is small, the holes injected into the active layer do not escape to the n-type clad layer side. Therefore, there is no waste of holes, which contributes to recombination in the active layer, and the operating voltage can be lowered as much as the bandgap energy of the n-type cladding layer is reduced, so that light emission with the same level of brightness as before can be achieved. To do.

The ratio of the band gap energy of the n-type cladding layer that can be reduced is about 1/2 of the band gap energy difference between the p-type cladding layer and the active layer because the effective mass of holes is about 3 times that of electrons. Can be A
The use of l _z Ga _1-z N material on the cladding layer, can be the ratio z of Al to less than half of the ratio of Al in the p-type cladding layer, the operation voltage can be lowered 5-10%.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a semiconductor light emitting device of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a cross-sectional explanatory view of a mesa-shaped semiconductor laser chip which is an embodiment of the semiconductor light emitting device of the present invention.
2 is a manufacturing process diagram thereof, and FIG. 3 is a schematic energy band diagram mainly showing a forbidden band of the n-type cladding layer, the active layer and the p-type cladding layer of the semiconductor light emitting device of the present invention.

In FIG. 1, 1 is sapphire (Al ₂ O
₃ single crystal) substrate made of n-type GaN,
The low temperature buffer layer 2 having a thickness of about 1 to 0.2 μm and n-type GaN, and the high temperature buffer layer 3 having a thickness of about 2 to 3 μm, an n-type material having a bandgap energy (forbidden band width) smaller than that of the p-type cladding layer, for example, Al _x Ga _1-x N (0 ≦ x ≦
0.5, for example x = 0.07), and 0.1 to
N-type cladding layer 4 having a thickness of about 0.3 μm, a material having a bandgap energy smaller than both cladding layers and being undoped or n-type or p-type and having a larger refractive index, for example, In _y Ga _1-y N (0 ≦ y ≦ 1) consists of 0.05
To about 0.1 μm active layer 5, p-type Al _z Ga _1-z N
(0 <z ≦ 1, 2x ≦ z, for example, z = 0.15), a p-type cladding layer having a thickness of about 0.1 to 0.3 μm, and a p-type G
A cap layer 7 made of aN and having a thickness of about 0.3 to 2 μm is sequentially laminated, and a p-side electrode 8 made of Au or the like is formed on the cap layer 7 and a part of the laminated semiconductor layer is removed by etching to expose the high temperature buffer. An n-side electrode 9 made of Al or the like is formed on the layer 3, and a current stripe is further formed. Therefore, a part of the cap layer 7 and the p-type cladding layer are etched to form a mesa shape, and a semiconductor laser chip is formed. Has been formed.

In the semiconductor light emitting device of the present invention, the bandgap energy of the n-type cladding layer 4 is smaller than the bandgap energy of the p-type cladding layer 6 as shown in the embodiment of the semiconductor laser described above, and these bandgap energies are smaller than those of the p-type cladding layer 6. A material having a gap energy larger than the band gap energy of the active layer 5 is used for both the clad layers 4 and 6 and the active layer 5.
Is formed.

A double heterojunction structure in which an active layer 5 made of a material having a small bandgap energy is sandwiched by a clad layer made of a material having a large bandgap energy in order to efficiently perform recombination of electrons and holes and increase luminous efficiency. Are used in semiconductor lasers and high-brightness LEDs. When a material with a large bandgap energy is used for the cladding layer, the effect of confining electrons and holes is increased, which contributes to light emission without waste, but the operating voltage is high, and the leakage of electrons and holes from the active layer is actually ignored. A material having a band gap energy that can be achieved is selected. However, the operating voltage is higher than that of the pn junction. In the present invention, the operating voltage can be lowered while maintaining such a degree that the leakage of electrons and holes can be ignored. That is, the effective mass of holes is as large as about three times the effective mass of electrons, and even if the band gap energy is small, the leakage is smaller than that of electrons. Therefore, by using a material having a bandgap energy smaller than the bandgap energy of the p-type clad layer for the n-type clad layer, injection of electrons into the active layer can be performed at a low voltage, and leakage of holes from the active layer can be prevented. It was made possible.

The operation of the present invention will be described in detail with reference to FIG. 3, which is a schematic view of the energy band diagram of the semiconductor laser of FIG. In FIG. 3, V is the valence band, F is the forbidden band, C is the conduction band energy band, and A is n.
-Type GaN high temperature buffer layer 3, B is n-type Al _0.07
The n-type cladding layer 4 made of Ga _0.93 N, and D is In _y Ga.
_The active layer 5 made of _1-y N, G shows a p-type cladding layer made of Al _0.15 Ga _0.85 N, and J shows an energy band in the range of the cap layer 7 made of p-type GaN.

In the semiconductor laser of this embodiment, as shown in FIG. 3, the band gap energy of the n-type cladding layer indicated by B is smaller than the band gap energy of the p-type cladding layer indicated by G. . Broken line B1
Shows the same bandgap energy as that of the p-type clad layer in the conventional structure.

In this structure, when a voltage is applied between the p-side electrode 8 and the n-side electrode 9, the electrons E flow from the n-type GaN (high temperature buffer layer A) side to the p side, and the conduction band of the active layer. K ₁
Pour into. At this time, since the band gap energy of the n-type cladding layer is low, the electrons E easily flow into the conduction band K _{1 of the} active layer, and the electrons are supplied to the active layer even at a low voltage.
The electrons E flowing into the conduction band K _{1 of the} active layer are pulled by the p-side electrode, but are confined in the active layer because the band gap energy of the p-type cladding layer is large. On the other hand, the holes H flow from the p-type GaN (contact layer J) side to the n side and flow into the valence band K ₂ of the active layer. The holes H flowing into the valence band K ₂ of the active layer are pulled to the n-side electrode, but the effective mass of the holes H is about three times as large as the effective mass of the electrons, and the band gap of the n-type cladding layer B is large. Even if the energy is low, it cannot be overcome and is effectively confined in the valence band of the active layer. As a result, electrons and holes are efficiently recombined in the active layer, and high luminous efficiency is obtained.

As described above, according to the present invention, each semiconductor layer is selected so that the bandgap energy of the n-type clad layer is smaller than that of the p-type clad layer. Electrons can be injected, and the luminous efficiency can be improved without increasing the reactive current. The degree to which the bandgap energy of the n-type clad layer is made smaller than that of the p-type clad layer is determined by the bandgap energy of the active layer, and due to the difference in bandgap energy from the active layer, 1/3 to 1 of the case of the p-type layer. It may be reduced by about / 2.

The general formula Al _p Ga _q In _1-pq N (0 ≦ p
<1, 0 <q ≦ 1, 0 <p + q ≦ 1) In order to reduce the bandgap energy by using the gallium nitride-based compound semiconductor consisting of (1), p should be small, that is, the Al composition ratio should be small, or p + q should be It is small, that is, it can be obtained by increasing the composition ratio of In. Therefore, by adjusting the composition ratio of Al and In so that the bandgap energy of the clad layer is larger than that of the active layer and the bandgap energy of the n-type clad layer is smaller than that of the p-type clad layer, A semiconductor layer having a band gap energy of

Since the embodiment shown in FIG. 1 is a semiconductor laser, it is necessary to confine light in the active layer to oscillate, so that the refractive index of the cladding layer is smaller than that of the active layer. In case of LED, it is not always necessary. However, if the Al composition ratio is increased with the above composition ratio, the refractive index becomes smaller.

Next, a method of manufacturing the semiconductor laser shown in FIG. 1 will be described with reference to FIG.

First, as shown in FIG. 2A, a substrate 1 made of sapphire or the like is coated with a low temperature buffer layer 2 made of gallium nitride compound semiconductor such as n-type GaN by 0.01 to 0.01 by MOCVD. The high temperature buffer layer 3 made of n-type GaN having the same composition is grown at a temperature of about 700 to 1200 ° C. to a thickness of about 2 to 5 μm.
Form a degree.

Next, by further supplying TMI, for example, n-type Al _x Ga _1-x N (0 ≦ x ≦ 0.5, for example x
= 0.07) and the n-type clad layer 4 of 0.1 to 0.
The thickness is about 3 μm. After that, TMI instead of TMA
To supply non-doped or n-type or p-type In _y G
The active layer 5 made of a _1-y N (0 ≦ y ≦ 1, for example y = 0.06) is grown to a thickness of about 0.05 to 0.1 μm. Then, using the same source gas as the source gas used to form the n-type cladding layer 4, TMA was added to the n-type cladding layer 4.
In the case of p-type Al _z Ga which is the p-type cladding layer 6, the p-type clad layer 6 is supplied to the reaction tube at a flow rate of 20 to 100 sccm, which is about double the above case.
_1-z N (0 <z ≦ 1, 2x ≦ z, for example z = 0.1
5) Form a layer of about 0.1 to 0.3 μm. Further, the same source gas as that for forming the buffer layer 3 is supplied to p-type GaN.
The cap layer 7 made of is formed to a thickness of 0.3 to 2 μm.

In order to form the above-mentioned buffer layer 3 and cladding layer 4 into an n-type, Si, Ge and Te are replaced with SiH ₄ and G.
In order to form a p-type cladding layer 6 or cap layer 7 by mixing impurities such as eH ₄ or TeH ₄ into the reaction gas, Mg or Zn is used as an organic metal gas of Cp ₂ Mg or DMZn. Mix in gas. However, in the case of n-type, even if no impurities are mixed in, N easily evaporates at the time of film formation and naturally becomes n-type, so that property may be utilized.

After that, a protective film 10 such as SiO ₂ or Si ₃ N ₄ is provided on the entire surface of the growth layer of the semiconductor layer (FIG. 2B).
), Annealing is performed at 400 to 800 ° C. for about 20 to 60 minutes to activate the p-type clad layer 6 and the cap layer 7, which are p-type layers.

When the annealing is completed, as shown in FIG. 2C, a mask such as a resist film 11 is provided and stacked until the n-type cladding layer 4 or the n-type high temperature buffer layer 3 is exposed. Etch the semiconductor layer. This etching is performed by reactive ion etching under an atmosphere of a mixed gas of Cl ₂ and BCl ₃ , for example.

Then, a metal film of Au, Al or the like is formed by sputtering or the like, and the p-side electrode 8 electrically connected to the p-type layer on the surface of the laminated compound semiconductor layer and the exposed high temperature buffer layer 3 surface. The n-side electrode 9 electrically connected to the n-type layer is formed, and the cap layer 7 and part of the p-type cladding layer 6 are mesa-etched (see FIG. 1).

Next, each chip is diced to form a semiconductor laser chip.

In the above-mentioned embodiment, the semiconductor laser of the mesa type current stripe structure has been described, but the semiconductor laser of various structures such as the current limiting layer buried type and the gallium nitride compound semiconductor such as the LED of the double heterojunction structure. The present invention can be applied to a semiconductor light emitting device using.
Further, the semiconductor material is not limited to the material of the composition of the above embodiment, and a material obtained by substituting a part or all of N of Al _p Ga _q In _1-pq N with As and / or P or a gallium arsenide-based compound semiconductor. The present invention can be similarly applied to a semiconductor light emitting device using.

[0041]

According to the semiconductor light emitting device of the present invention, since the semiconductor material is selected so that the bandgap energy of the n-type cladding layer is smaller than that of the p-type cladding layer, the reactive current is reduced. Less
In addition, it is possible to emit light with high brightness at a low operating voltage, and it is possible to obtain a semiconductor light emitting device with high light emission efficiency.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view of an embodiment of a semiconductor light emitting device of the present invention.

2A and 2B are cross-sectional explanatory views showing the manufacturing process of FIG.

FIG. 3 is an energy band diagram mainly showing a forbidden band of a clad layer and an active layer of an embodiment of a semiconductor light emitting device of the present invention.

FIG. 4 is a perspective view showing an example of a conventional semiconductor light emitting device.

[Explanation of symbols]

1 substrate 4 n-type clad layer 5 Active layer 6 p-type clad layer

Continuation of front page (56) Reference JP-A-4-97378 (JP, A) JP-A 1-217986 (JP, A) JP-A 4-111375 (JP, A) JP-A-6-268259 (JP , A) M.M. R. S. Symp. Proc. Diamond, SiC and Nitride Wide Bandgap Semiconductor, Vol. 339 (1994.4), p. 443-452 Appl. Phys. Lett. , 64 [13] (1994), p. 1687-1689 Jpn. J. Appl. Phys. Part 2, Vol. 32 No. 1A / B (1993), p. L8-L11 (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 33/00 H01S 5/00-5/50

Claims (30)

(57) [Claims] 1. An n-type clad layer made of n-type AlGaN and a p-type clad layer made of p-type AlGaN
It has a sandwich structure sandwiching an active layer made of GaN, and reduces the Al ratio of the n-type cladding layer while keeping the Al ratio of the p-type cladding layer constant to reduce the band of the active layer. and less than half of the Al ratio of the p-type cladding layer defined by gap energy, the band gap energy of the n-type cladding layer, the difference between the band gap energy of the active layer and the band gap energy of the p-type cladding layer wherein the semiconductor light emitting device of double hetero junction type, characterized by being configured so that 1 / 3-1 / 2 of the difference between the band gap energy of the active layer. 2. The n-type cladding layer is connected to an n-side electrode, and a buffer layer made of GaN is interposed between the n-type clad layer and the n-side electrode. Semiconductor light emitting device. 3. An n-type clad layer made of n-type AlGaN and a p-type clad layer made of p-type AlGaN
It has a sandwich structure sandwiching an active layer made of GaN, and reduces the Al ratio of the n-type cladding layer while keeping the Al ratio of the p-type cladding layer constant to reduce the band of the active layer. and less than half of the Al ratio of the p-type cladding layer defined by gap energy, the band gap energy of the n-type cladding layer, the difference between the band gap energy of the active layer and the band gap energy of the p-type cladding layer wherein of the difference between the band gap energy of the active layer 1/3 as a 1/2, prior
It injected from the serial n-type cladding layer of electrons to the active layer, before
The bandgap energy of the n-type cladding layer is set to p
Equal to the bandgap energy of the clad layer
If compared with to allow a low voltage and a hole effective mass is utilizing larger than the effective mass of the electrons effectively confine holes in the valence band of the active layer, before
And the serial active layer can prevent leakage of holes into the n-type cladding layer, double heterojunction semiconductor light emitting device is characterized in that so as not to increase the reactive current. 4. The n-type clad layer is connected to an n-side electrode, and a buffer layer made of GaN is interposed between the n-type clad layer and the n-side electrode. Semiconductor light emitting device. 5. A substrate and an n-type G provided on the substrate
a buffer layer made of aN, an n-type cladding layer made of n-type AlGaN provided on the buffer layer,
An active layer made of InGaN provided on the clad layer and a p-type clad layer made of p-type AlGaN provided on the active layer, and an Al ratio of the p-type clad layer.
The Al ratio of the n-type cladding layer is reduced while keeping the ratio constant to be half or less of the Al ratio of the p-type cladding layer determined by the bandgap energy of the active layer, and the bandgap of the n-type cladding layer is reduced. the energy difference between the band gap energy of the active layer before
Of the difference between the band gap energy of the serial p-type band-gap energy of the cladding layer and the active layer 1 / 3-1 /
As a 2, electron injection from the n-type cladding layer to the active layer, Bandogya of the n-type cladding layer
Band energy of the p-type cladding layer
The effective mass of holes is larger than the effective mass of electrons as compared with the case where the energy is equal to the energy, and the holes are used to make holes effective in the valence band of the active layer.
A double-heterojunction type light emitting diode , characterized in that it is effectively confined in the inside to prevent holes from leaking from the active layer to the n-type clad layer, thereby preventing an increase in reactive current. 6. A substrate and an n-type G provided on the substrate
a buffer layer made of an aN layer and a GaN layer provided on the buffer layer.
ReRuan n-type clad layer made of n-type AlGaN,
Provided on the mold cladding layerRuInGaN active layer
And p-type AlGaN provided on the active layer
Provided on the p-type clad layer and the p-type clad layer
and a cap layer made of p-type GaN,The p-type club
While keeping the Al ratio of the dead layer constantThe n-type cladding
The band gap of the active layer is reduced by reducing the Al ratio of the layer.
The Al ratio determined by the
The bandgap energy of the pad layer is compared with the bandgap energy of the active layer.
And the gap energyThe abovep-type cladding layer
Band gap energy and band gap of the active layer.
The difference between1/3 ~1 /2 andTo beWest
The injection of electrons into the active layerThe n-type cladding layer
Band gap energy of the p-type cladding layer
Band gap energy compared toLow
In addition to the voltage, the effective mass of holes is
Utilizing the fact that it is larger than the effective mass ofHoles said activity
Effectively confined within the valence band of the layer,From the active layer
to prevent holes from leaking into the n-type cladding layer
It is characterized in that the reactive current is not increased.
Semiconductor laser. 7. The semiconductor laser according to claim 6, wherein the substrate is a sapphire substrate. 8. An InG composed of an n-type clad layer made of n-type AlGaN and a p-type clad layer made of p-type AlGaN.
It has a sandwich structure sandwiching an active layer made of aN and effectively confine holes in the valence band of the active layer,
To the extent that it is possible to prevent leakage of holes into the n-type cladding layer from the active layer, to lower the bandgap energy of the n-type cladding layer, the injection of electrons into the active layer, the n Band gap energy of the mold clad layer
Bandgap energy of the p-type cladding layer
So that the Al ratio of the n-type clad layer can be set to be lower than that of the p-type clad layer.
A semiconductor light emitting device characterized in that the reactive current is prevented from increasing by reducing the value determined by the bandgap energy of the active layer while keeping the Al ratio constant . 9. The n-type cladding layer is connected to an n-side electrode, and a buffer layer made of GaN is interposed between the n-type clad layer and the n-side electrode. Semiconductor light emitting device. 10. An n-type clad layer made of n-type AlGaN and a p-type clad layer made of p-type AlGaN
It has a sandwich structure sandwiching an active layer made of GaN, and reduces the Al ratio of the n-type cladding layer while keeping the Al ratio of the p-type cladding layer constant to reduce the band of the active layer. as a value determined by the gap energy, by lowering the band gap energy of the n-type cladding layer, the electron injection from the n-type cladding layer to the active layer, the band gap energy of the n-type cladding layer
Is the bandgap energy of the p-type cladding layer
Together to allow as compared with the case of equal over a low voltage, the hole effective mass is utilizing larger than the effective mass of the electron effective holes into the valence band of the active layer
The semiconductor light emitting device is characterized in that it is confined in the above structure so that holes can be prevented from leaking from the active layer to the n-type clad layer so that the reactive current is not increased. 11. The n-type clad layer is connected to an n-side electrode, and a buffer layer made of GaN is interposed between the n-type clad layer and the n-side electrode. Semiconductor light emitting device. 12. An n-type clad layer made of n-type AlGaN and a p-type clad layer made of p-type AlGaN
It has a sandwich structure sandwiching an active layer made of GaN, and reduces the Al ratio of the n-type cladding layer while keeping the Al ratio of the p-type cladding layer constant to reduce the band of the active layer. The Al ratio is determined by the gap energy, and the bandgap energy of the n-type cladding layer is lowered so that electrons are injected from the n-type cladding layer to the active layer by the bandgap energy of the n-type cladding layer.
Bandgap energy of the p-type cladding layer
And the effective mass of the holes is larger than the effective mass of the electrons, so that the holes are effectively transferred to the valence band of the active layer.
Confinement, so as to be prevented from leaking holes into the n-type cladding layer from the active layer, so as not to increase the reactive current, and the film thickness of the active layer to the extent that it becomes possible lasing be A semiconductor laser characterized by: 13. The semiconductor laser according to claim 12, wherein the sandwich structure is provided on a substrate, and a buffer layer made of at least GaN is provided between the sandwich structure and the substrate. 14. The sandwich structure according to claim 12 or 13, characterized in that with provided on the substrate, wherein the substrate opposite the gap layer composed of at least GaN on the surface side of the sandwich structure is provided The semiconductor laser described. 15. The cap layer and a portion of the sandwich structure are etched into a mesa shape .
15. The semiconductor laser according to claim 14, wherein: 16. An n-type AlGaN layer and a p-type AlGaN
The p-type cladding layer has a sandwich structure sandwiching an InGaN layer, and the Al ratio of the n-type AlGaN layer is reduced while keeping the Al ratio of the p-type cladding layer constant.
The Al ratio of the p-type AlGaN layer determined by the band gap energy of the nGaN layer is half or less,
The bandgap energy of the AlGaN layer is
the difference between the band gap energy of nGaN layer is the p
Type band gap energy of the AlGaN layer and the In
1/3 of the difference between the band gap energy of GaN layer
A double-heterojunction type semiconductor light-emitting device, which is configured to have a ratio of 1/2 . 17. The n-type AlGaN layer is connected to an n-side electrode, and a buffer layer made of GaN is interposed between the n-type electrode and the n-side electrode. Semiconductor light emitting device. 18. An n-type AlGaN layer and a p-type AlGaN
The p-type AlGaN layer has a sandwich structure sandwiching an InGaN layer, and the Al ratio of the p-type AlGaN layer is kept constant.
In addition, the Al ratio of the n-type AlGaN layer is reduced to half or less of the Al ratio of the p-type AlGaN layer determined by the bandgap energy of the InGaN layer, and the bandgap energy of the n-type AlGaN layer is set to the InGaN layer. the difference between the band gap energy between the bandgap energy of the p-type AlGaN layer I of
1/3 of the difference from the band gap energy of the nGaN layer
~ As a 1/2, the electron injection from the n-type AlGaN layer to <br/> the InGaN layer, the n-type AlGa
The band gap energy of the N layer is set to the p-type AlGaN
Compared with equalization of layer bandgap energy
Together to allow a low voltage by, before the hole hole effective mass by utilizing larger than the effective mass of the electron
The InGa is effectively confined within the valence band of the active layer.
A double-heterojunction type semiconductor light-emitting device, characterized in that holes can be prevented from leaking from the N layer to the n-type AlGaN layer so that the reactive current is not increased. 19. The n-type AlGaN layer is connected to an n-side electrode, and a buffer layer made of GaN is interposed between the n-type electrode and the n-side electrode. Semiconductor light emitting device. 20. A substrate, an n-type buffer layer provided on the substrate and made of an n-type GaN layer, an n-type AlGaN layer provided on the n-type buffer layer, and the n-type AlG.
an InGaN layer provided on the aN layer and the InGaN layer
And a p-type AlGaN layer provided on the layer, the p-type
While maintaining the Al ratio of the AlGaN layer constant, the n-type A
The p-type Al determined by the band gap energy of the InGaN layer by reducing the Al ratio of the lGaN layer.
The Al ratio of the GaN layer is half or less, and the n-type AlGa
The band gap energy of the N layer, the difference between the band gap energy of the InGaN layer is the p-type AlGa
In the Do <br/> so that the 1 / 3-1 / 2 of the difference between the band gap energy of the N layer and the band gap energy of the InGaN layer, the from the n-type AlGaN layer InGa
The injection of electrons into the N layer causes the band of the n-type AlGaN layer to be
The gap energy of the p-type AlGaN layer
In addition to making the hole energy equal to the cap energy, it can be performed at a lower voltage, and the fact that the effective mass of holes is larger than the effective mass of electrons is used to generate holes.
Effectively confined within the valence band of the layer, especially that from said InGaN layer so as to be prevented from leaking holes into the n-type AlGaN layer, and so as not to increase the reactive current
A double-heterojunction type light emitting diode. 21. A substrate, a buffer layer made of n-type GaN provided on the substrate, and the n-type AlGaN layer that <br/> provided on the buffer layer, provided on the n-type AlGaN layer It includes a InGaN layer that includes a p-type AlGaN layer provided on the InGaN layer, and a cap layer made of is that p-type GaN is provided on the p-type AlGaN layer, before
The Al ratio of the n-type AlGaN layer is reduced while keeping the Al ratio of the p-type AlGaN layer constant, and the InG
and Al ratio determined by the band gap energy of aN layer, the band gap of the n-type band gap energy of the AlGaN layer, the difference between the band gap energy of the InGaN layer is the p-type AlGaN layer band gap energy and the InGaN layer of of the difference between energy 1/3 as a 1/2, the InGa
The injection of electrons into the N layer causes the band of the n-type AlGaN layer to be
The gap energy of the p-type AlGaN layer
In addition to making the hole energy equal to the cap energy, it can be performed at a lower voltage, and the fact that the effective mass of holes is larger than the effective mass of electrons is used to generate holes.
A semiconductor laser which is effectively confined in a valence band of a layer to prevent holes from leaking from the InGaN layer to the n-type AlGaN layer so as not to increase a reactive current. 22. The semiconductor laser according to claim 21, wherein the substrate is a sapphire substrate. 23. An n-type AlGaN layer and a p-type AlGaN
The layer has a sandwich structure sandwiching an InGaN layer, and holes are effectively closed in the valence band of the InGaN layer.
In order to prevent the leakage of holes from the InGaN layer to the n-type AlGaN layer, the n-type A
The band gap energy of lGaN layer was low, injection of electrons into the InGaN layer, the n-type AlGaN
The band gap energy of the layer to the p-type AlGaN layer
Compared to the case where the band gap energy of
Of the n-type AlGaN layer so that it can be performed at a low voltage.
Keep the Al ratio of the p-type AlGaN layer constant.
A semiconductor light emitting device, characterized in that the reactive current is prevented from increasing by keeping the value as determined by the band gap energy of the InGaN layer unchanged . 24. The n-type AlGaN layer is connected to an n-side electrode, and a buffer layer made of GaN is interposed between the n-type electrode and the n-side electrode. Semiconductor light emitting device. 25. An n-type AlGaN layer and a p-type AlGaN
The p-type AlGaN layer has a sandwich structure sandwiching an InGaN layer with the layer, and the Al ratio of the p-type AlGaN layer is maintained as a unit.
In addition, the band gap energy of the n-type AlGaN layer is lowered to a value determined by the band gap energy of the InGaN layer by reducing the Al ratio of the n-type AlGaN layer, The injection of electrons into the InGaN layer depends on the n-type AlGaN.
The band gap energy of the layer to the p-type AlGaN layer
Compared to the case where the band gap energy of
Together to allow a low voltage, the hole effective mass is the hole by using a larger than the effective mass of electrons the Te
The InGaN is effectively confined within the valence band of the active layer.
A semiconductor light-emitting device, characterized in that it is possible to prevent holes from leaking from the layer to the n-type AlGaN layer so as not to increase the reactive current. 26. The n-type AlGaN layer is connected to an n-side electrode, and a buffer layer made of GaN is interposed between the n-type electrode and the n-side electrode. Semiconductor light emitting device. 27. An n-type AlGaN layer and a p-type AlGaN
The p-type AlGaN layer has a sandwich structure sandwiching an InGaN layer between the layers, and the Al ratio of the p-type AlGaN layer is kept constant.
In addition, the Al ratio of the n-type AlGaN layer is reduced to an Al ratio determined by the bandgap energy of the InGaN layer, and the bandgap energy of the n-type AlGaN layer is lowered to change the n-type AlGaN layer to the InGaN layer. Injection of electrons into the n-type AlGaN layer
Band gap energy of the p-type AlGaN layer
In comparison with the case where the bandgap energy is made equal, it can be performed at a lower voltage, and the fact that the effective mass of holes is larger than the effective mass of electrons is used to activate the holes.
Effectively confined valence band of sexual layer, and from the InGaN layer can be prevented leakage of holes into the n-type AlGaN layer, so as not to increase the reactive current, and before
The film thickness of the serial InGaN layer to the extent that it is possible to laser oscillation
A semiconductor laser characterized by: 28. The semiconductor laser according to claim 27, wherein the sandwich structure is provided on a substrate, and a buffer layer made of at least GaN is provided between the sandwich structure and the substrate. 29. The sandwich structure according to claim 27 or 28, characterized in that with provided on the substrate, a cap layer composed of at least GaN is provided on the front surface side of the substrate opposite of the sandwich structure The semiconductor laser described. 30. A portion of the cap layer and the sandwich structure is etched into a mesa shape .
30. The semiconductor laser according to claim 29, wherein: