JPH09331082A - Semiconductor light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor light emitting element enhancing its light emitting efficiency and delaying its deterioration by suppressing generation of a defect species becoming a nonradiative recombination center in a p-type conductive layer. SOLUTION: An n-type clad layer 2, a guide layer 3, an active layer 4, a guide layer 5 and a p-type clad layer 6 formed of II-VI compound semiconductor are sequentially stacked on an n-type GaAs substrate 1. An n-type impurity such as chlorine is added to the layer 2. Nitrogen is added as a p-type impurity to the layer 6. The chlorine of the n-type impurity is added in a smaller amount than the p-type impurity. Thus, in the layer 6, generation of a defect seed becoming a nonradiative recombination center is suppressed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to p with an active layer in between.
The present invention relates to a semiconductor light emitting device in which a type conductive layer and an n type conductive layer are laminated.

[0002]

2. Description of the Related Art In recent years, active research has been conducted on semiconductor light-emitting devices capable of emitting green and blue light in response to demands for high-density and high-resolution recording / playback for optical discs and magneto-optical discs, and demands for full-color indoor / outdoor displays. Has been done.

Materials that constitute such a semiconductor light emitting device capable of emitting green or blue light include zinc (Zn), mercury (Hg), cadmium (Cd), magnesium (Mg), and beryllium (Be) of the II group elements. At least one of the above) and a group VI element sulfur (S), selenium (Se),
II consisting of at least one of tellurium (Te) II
Group VI compound semiconductors are promising. In particular, ZnMgS
Se mixed crystal is Ga of gallium (Ga) and arsenic (As).
It is known that it is possible to grow crystals on an As mixed crystal substrate and is suitable for a guide layer or a clad layer when manufacturing a semiconductor light emitting device such as a blue semiconductor laser (for example, El
ectronics Letters 28 (1992) p1798).

Further, the semiconductor light emitting element has a structure in which a p-type conductive layer made of a p-type cladding layer or the like and an n-type conductive layer made of an n-type cladding layer are formed with an active layer interposed therebetween. Each of these layers is generally formed by sequentially stacking on a substrate by a molecular beam epitaxy (MBE) method. In the case of forming a semiconductor light emitting device with a II-VI group compound semiconductor, GaAs or ZnS which has excellent crystallinity and is easily available as a substrate.
Each layer made of a II-VI group compound semiconductor is sequentially laminated thereon by using e or the like directly or via a buffer layer. At this time, in order to obtain a semiconductor light emitting device that can obtain green or blue light emission with high luminous efficiency, it is necessary to increase the crystallinity of each layer formed of the II-VI group compound semiconductor.

[0005]

However, the conventional p-type conductive layer to which, for example, nitrogen (N) is added generally does not have good optical characteristics, and shows the same carrier concentration in terms of photoluminescence intensity. It is lower than that of the n-type conductive layer by one digit or more. This indicates that the injected carriers do not emit light but recombine, and many crystal defects (non-radiative recombination centers) causing such non-radiative recombination are present in the p-type conductive layer. It is possible that it exists.

As a defect species which is easily generated in the p-type conductive layer, a negatively charged acceptor impurity (for example, N) is used.
^- ) Is a positively charged defect (for example, a defect involving Se vacancies) (for example Ph
ysical Review Letters 74 p1131 (1995). That is, it is considered that such a defect species acts as a non-radiative recombination center and deteriorates the optical characteristics of the p-type conductive layer.

As described above, in the conventional semiconductor light emitting device, p
Since the crystallinity of the mold conductive layer was not high, sufficient luminous efficiency could not be obtained, and the emission intensity was rapidly deteriorated, resulting in problems in optical characteristics and reliability.

The present invention has been made in view of the above problems, and an object thereof is to increase the luminous efficiency by suppressing the generation of defect species which become non-radiative recombination centers in the p-type conductive layer. An object is to provide a semiconductor light emitting device that can slow deterioration.

[0009]

A semiconductor light emitting device according to the present invention comprises a p-type conductive layer and an n-type conductive layer stacked with an active layer interposed therebetween, and at least a part of the p-type conductive layer. The structure is such that an n-type impurity is added to.

In this semiconductor light emitting device, a p-type conductive layer and an n-type conductive layer are provided.
When a predetermined voltage is applied to the p-type conductive layer, a current is injected into the p-type conductive layer, and light emission occurs due to electron-hole recombination in the active layer. Here, in the p-type conductive layer, the added n-type impurity suppresses the generation of defect species that become non-radiative recombination centers, and suppresses electron-hole recombination that does not contribute to light emission.

[0011]

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 shows a structure of a semiconductor light emitting device according to an embodiment of the present invention. This semiconductor light emitting device has a structure in which I
An n-type clad layer 2, a guide layer 3, an active layer 4, a guide layer 5 and a p-type clad layer 6 each made of a group I-VI compound semiconductor are sequentially laminated.

The n-type cladding layer 2 has a thickness of about 70, for example.
It is formed by a ZnMgSSe mixed crystal of 0 nm, and n
An n-type conductive layer is formed by adding chlorine (Cl) as a type impurity. Note that chlorine is added so that the impurity concentration becomes, for example, 4 × 10 ¹⁷ cm ⁻³ .

The guide layer 3 is formed of, for example, a ZnS _0.06 Se _0.94 mixed crystal having a thickness of about 60 nm. The active layer 4 is formed of, for example, a Zn _0.85 Cd _0.15 Se mixed crystal having a single quantum well structure with a thickness of about 6 to 12 nm. The guide layer 5 is, for example, ZnS having a thickness of about 60 nm.
It is formed of _0.06 Se _0.94 mixed crystal. N-type and p-type impurities are not added to the guide layer 3, the active layer 4, and the guide layer 5.

The p-type cladding layer 6 has a thickness of, for example, about 50.
It is formed by a ZnMgSSe mixed crystal of 0 nm, and p
By adding nitrogen (N) as a type impurity, p
It is used as a mold conductive layer. It should be noted that nitrogen is added so that the impurity concentration is, for example, 6 × 10 ¹⁶ cm ⁻³ . The p-type cladding layer 6 also contains chlorine (C, which is an n-type impurity).
l) is also added. The concentration of chlorine added is, for example, 1 × 10 ¹⁶ cm ^−3, which is lower than the concentration of nitrogen added and is set so as not to significantly change the original properties of the p-type cladding layer 6. As a result, the final nitrogen impurity concentration in the p-type cladding layer 6 is 5 × 10 ¹⁶ cm ⁻³ .

On the p-type clad layer 6, each layer for making good ohmic contact with the p-side electrode, that is, the first semiconductor layer 7 and the second semiconductor layer formed of a II-VI group compound semiconductor, respectively. The semiconductor layer 8, the superlattice semiconductor layer 9 and the contact layer 10 are sequentially stacked.

The first semiconductor layer 7 has a thickness of, for example, about 50.
The second semiconductor layer 8 is formed of a ZnSSe mixed crystal of 0 nm, and the second semiconductor layer 8 is formed of ZnSe having a thickness of about 100 nm, for example. The superlattice semiconductor layer 9 is formed by alternately stacking ZnSe and ZnTe. The contact layer 10 is made of ZnTe.

Each of the first semiconductor layer 7, the second semiconductor layer 8, the superlattice semiconductor layer 9 and the contact layer 10 is made into a p-type conductive layer by adding nitrogen as a p-type impurity. ing. That is, in the present embodiment, the p-type cladding layer 6, the first semiconductor layer 7, the second semiconductor layer 7
Semiconductor layer 8, superlattice semiconductor layer 9 and contact layer 1
0 layers form a p-type conductive layer. Note that nitrogen has an impurity concentration of, for example, 2 × in the first semiconductor layer 7.
10 ¹⁷ cm ⁻³ , 1 × 10 ¹⁸ c in the second semiconductor layer 8
m ^-3, the superlattice semiconductor layer 9 2 × 10 ¹⁸ cm ^-3, is added, respectively, as in the contact layer 10 becomes 5 × 10 ¹⁸ cm ^-3.

The superlattice semiconductor layer 9 and the contact layer 10 have a strip shape with a width of 10 μm, for example. An insulating layer 11 made of, for example, alumina (Al ₂ O ₃ ) is formed in a region on the second semiconductor layer 8 where the superlattice semiconductor layer 9 and the contact layer 10 are not formed.

A p-side electrode 12 is provided on the insulating layer 11 and the contact layer 10. The p-side electrode 12 is made of, for example, 10 nm thick palladium (Pd),
For example, platinum (Pt) having a thickness of 100 nm and gold (Au) having a thickness of 300 nm, for example, are sequentially stacked from the contact layer 10 side. On the back surface of the substrate 1, an n-side electrode 13 made of indium (In) is formed.
Is provided.

The semiconductor light emitting device having such a structure can be manufactured as follows.

First, a molecular beam epitaxy (MBE) is formed on a substrate 1 made of n-type GaAs.
taxy) method, the n-type cladding layer 2, the guide layer 3, the active layer 4, the guide layer 5, the p-type cladding layer 6, the first semiconductor layer 7, the second semiconductor layer 8, the superlattice semiconductor layer 9 and the contact. Layer 10 is sequentially epitaxially grown.

This epitaxial growth is performed by the MBE apparatus as shown in FIG. This MBE apparatus is a type of vacuum vapor deposition apparatus, and includes a vacuum container 21 connected to an ultrahigh vacuum exhaust device (not shown). A substrate holder 22 is arranged inside the vacuum container 21, and the substrate 1 is held therein.

A plurality of molecular beam source cells (for example, Knudsen cells (K cells)) 23 are arranged in the vacuum container 21 so as to face the substrate 1 held by the substrate holder 22. Inside each molecular beam source cell 23, raw materials corresponding to constituent elements of the II-VI group compound semiconductor epitaxially grown on the substrate 1 (group II elements such as zinc and magnesium and group VI elements such as sulfur and selenium). And a raw material corresponding to chlorine added as an n-type impurity.

The vacuum chamber 21 is also provided with a plasma generating chamber 24 for converting nitrogen added as a p-type impurity into plasma and irradiating it toward the GaAs substrate 1. The plasma generation chamber 24 is, for example, as shown in FIG. 2, an ECR (Electron Cycrotron Rcsonance).
It is composed of cells. This ECR cell has magnet 2
Microwaves are supplied from the microwave terminal 26 into the cell surrounded by 5 and nitrogen gas is supplied from the gas introduction pipe 27 to convert nitrogen into plasma.

N-type clad layer 2, guide layer 3, active layer 4, guide layer 5, p-type clad layer 6, first semiconductor layer 7, second semiconductor layer 8, superlattice semiconductor layer 9 and contact layer 10. When each is formed on the substrate 1, each particle beam of the group II element and the group VI element is irradiated from each molecular beam source cell 23 to grow each group II-VI compound semiconductor.

At this time, when the n-type cladding layer 2 which is the n-type conductive layer is formed, a chlorine particle beam is added to the molecular beam source in addition to the appropriately selected particle beams of the group II element and the group VI element. Irradiate from the cell 23 to add chlorine. In addition, the p-type clad layer 6, the first semiconductor layer 7, the second semiconductor layer 8, the superlattice semiconductor layer 9, and the contact layer 10 which are p-type conductive layers.
In the case of forming each of the above, each of the particle beams of the group II element and the group VI element selected appropriately is irradiated with nitrogen generated by plasma generation by applying a magnetic field and a microwave from the plasma generation chamber 24. Add each.

Further, when the p-type cladding layer 6 is formed, not only is plasma nitrogen irradiated, but also a chlorine particle beam is irradiated from the molecular beam source cell 23 to add chlorine. The chlorine impurity concentration is adjusted by changing the heating temperature of the chlorine molecular beam source cell 23, and the nitrogen impurity concentration is adjusted by changing the plasma output (for example, the electric power supplied to the plasma generation chamber 24). By doing.

Next, a resist is applied on the contact layer 9 to form a belt-shaped mask pattern (not shown) by photolithography, and then wet etching or dry etching is performed using the mask pattern as a mask to form the contact layer 10 and Superlattice semiconductor layer 9
Are selectively removed to form a band. After that, alumina is vapor-deposited on the second semiconductor layer 8 from which the contact layer 10 and the superlattice semiconductor layer 9 have been selectively removed, and the mask pattern is removed together with the alumina formed on the mask pattern ( The insulating layer 11 is formed by lift-off.

Further, palladium, platinum and gold are sequentially deposited on the insulating layer 11 and the contact layer 10 to form the p-side electrode 12. Further, on the back surface of the substrate 1, the In solder used for fixing to the substrate holder during growth is diverted as the n-side electrode 13. As a result, the semiconductor light emitting device having the configuration shown in FIG. 1 is formed.

Next, the operation of this semiconductor light emitting device will be described.

In this semiconductor light emitting device, when a predetermined voltage is applied between the p-side electrode 12 and the n-side electrode 13, a current is injected from the p-side electrode 12 into the contact layer 10. The current injected into the contact layer 10 passes through the superlattice semiconductor layer 9, the second semiconductor layer 8, the first semiconductor layer 7, the p-type cladding layer 6 and the guide layer 5 and is injected into the active layer 4. It In the active layer 4, light emission due to electron-hole recombination occurs.

Here, in the p-type cladding layer 6, at the time of growth, a part of the negatively charged p-type impurity nitrogen is electrically compensated by the positively charged n-type impurity chlorine. This suppresses the generation of new positively charged defect species that are thought to act as non-radiative recombination centers. That is, generation of electron-hole recombination that does not contribute to light emission is suppressed.

In order to confirm the effect of the semiconductor light emitting device according to this embodiment, the optical characteristics of this semiconductor light emitting device were compared with those of the conventional semiconductor light emitting device. The conventional semiconductor light emitting device used here has the same structure as the semiconductor light emitting device of the present embodiment, except that chlorine, which is an n-type impurity, is not added to the p-type cladding layer.

FIG. 3 shows the photoluminescence intensity from the p-type cladding layer 6. In FIG. 3, the horizontal axis represents wavelength and the vertical axis represents emission intensity. According to this, it can be seen that the semiconductor light emitting element of the present embodiment emits green or blue light stronger than the conventional one. That is, according to the semiconductor light emitting device of the present embodiment, the density of non-radiative recombination centers in the p-type cladding layer 6 can be reduced, and the luminous efficiency can be improved.

FIG. 4 shows changes with time of the emission intensity from the active layer. In FIG. 4, the horizontal axis represents time and the vertical axis represents emission intensity. According to this, it is understood that the deterioration of the semiconductor light emitting device of the present embodiment is about three times slower than that of the conventional device. That is, according to the semiconductor light emitting element of the present embodiment, it is possible to prevent deterioration of the element when light is emitted for a long period of time.

As described above, according to the semiconductor light emitting device of this embodiment, since chlorine, which is an n-type impurity, is added to the p-type cladding layer 6, non-radiative recombination in the p-type cladding layer 6 is performed. It is possible to suppress the generation of a defect species that becomes the center and improve the crystallinity of the p-type cladding layer 6. As a result, the light emission efficiency can be improved and the element life can be extended by delaying the deterioration.

The present invention has been described above with reference to the embodiments, but the present invention is not limited to the above embodiments, and various modifications can be made. For example, in the above-described embodiment, the n-type impurity is added only to the p-type cladding layer 6, but the p-type conductive layers other than the p-type cladding layer 6 (that is, the first semiconductor layer 7 and the second semiconductor layer 7). You may make it add an n-type impurity to some or all of the semiconductor layer 8, the superlattice semiconductor layer 9, and the contact layer 10). However, n
Similar to the above-described embodiment, the doping concentration of the type impurities needs to be lower than the doping concentration of the p-type impurities in each layer so that the original properties of each layer are not significantly changed.

Further, in the above-mentioned embodiment, the p-type impurity is not added to the guide layer 4, but it is also possible to add the p-type impurity to a part or the whole of the guide layer 4 to form a p-type conductive layer. In this case, the n-type impurity may be added to the region of the guide layer 4 to which the p-type impurity is added.
Also in this case, the addition concentration of the n-type impurity is set lower than that of the p-type impurity as in the above-described embodiment so that the original property of the guide layer to which the p-type impurity is added is not significantly changed. There is a need.

Further, in the above embodiment, the n-type impurity is added to the entire p-type cladding layer 6, but it may be added only to a part of the p-type cladding layer 6. This is also the case when adding an n-type impurity to another p-type conductive layer.

In addition, the semiconductor light emitting device according to the present invention is
The p-type impurity concentration and the n-type impurity addition concentration can be appropriately determined without being limited to the values described in the above embodiments.

Furthermore, in the above embodiment, n
Although chlorine is selected as the type impurity, at least one element selected from chlorine, gallium, and indium may be arbitrarily selected as the n-type impurity.

In addition, in the above embodiment,
Although the n-type clad layer 2, the active layer 4, and the p-type clad layer 6 are sequentially laminated on the n-type substrate 1, the semiconductor light emitting device according to the present invention has a p-type substrate and a p-type clad layer 6. It also includes the case where the type clad layer, the active layer, and the n-type clad layer are sequentially laminated.

Furthermore, the semiconductor light emitting device according to the present invention comprises an n-type cladding layer 2, a guide layer 3, an active layer 4, a guide layer 5, a p-type cladding layer 6, a first semiconductor layer 7, and a second semiconductor. The composition of the II-VI group compound semiconductors forming the layer 8, the superlattice semiconductor layer 9, and the contact layer 10 is not limited to the above-described embodiment, but zinc as a group II element,
The same applies as long as it contains at least one member selected from the group consisting of mercury, cadmium, magnesium and beryllium and at least one member selected from the group consisting of sulfur, selenium and tellurium as group VI elements. .

In addition, in the above embodiment,
The n-type cladding layer 2, guide layer 3, active layer 4, guide layer 5, p-type cladding layer 6, first semiconductor layer 7, second semiconductor layer 8, superlattice semiconductor layer 9 and contact layer 10
Each of them is made of a group I-VI compound semiconductor.
The present invention can also be applied to the case where they are made of compound semiconductors other than II-VI compound semiconductors such as IV compound semiconductors. In this case, the types of p-type impurities and n-type impurities to be added are appropriately selected according to the composition of the compound semiconductor.

In addition to the above, the semiconductor light emitting device according to the present invention is not limited to the structure described in the above-mentioned embodiment, and Zn between the substrate 1 and the n-type cladding layer 2 is not limited.
Various modifications are possible such as inserting a buffer layer made of Se.

[0047]

As described above, according to the semiconductor light emitting device of the present invention, the n-type impurity is added to at least a part of the p-type conductive layer, so that the non-light-emission reproducibility in the p-type conductive layer is increased. It is possible to suppress the generation of defect species serving as a bond center and improve the crystallinity of the p-type conductive layer. Therefore, it is possible to improve the luminous efficiency of the device, and it is possible to achieve the effect of slowing the deterioration and prolonging the life of the device.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a structure of a semiconductor light emitting device according to an embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of an MBE device used when forming the semiconductor light emitting device shown in FIG.

FIG. 3 is a characteristic diagram showing photoluminescence intensity from a p-type cladding layer of the semiconductor light emitting device shown in FIG.

FIG. 4 is a characteristic diagram showing the change over time in the emission intensity of the semiconductor light emitting device shown in FIG.

[Explanation of symbols]

1 ... Substrate, 2 ... N-type clad layer, 3 ... Guide layer, 4 ... Active layer, 5 ... Guide layer, 6 ... P-type clad layer, 7 ... First semiconductor layer, 8 ... Second semiconductor layer, 9 ... Superlattice semiconductor layer,
10 ... Contact layer, 11 ... Insulating layer, 12 ... P-side electrode,
13 ... N-side electrode, 21 ... Vacuum container, 22 ... Substrate holder, 23 ... Molecular beam source cell, 24 ... Plasma generation chamber, 25
... magnet, 26 ... microwave terminal, 27 ... gas introduction tube

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroyuki Okuyama 6-735 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (3)

[Claims] 1. A semiconductor light emitting device comprising a p-type conductive layer and an n-type conductive layer stacked with an active layer interposed therebetween, wherein an n-type impurity is added to at least a part of the p-type conductive layer. A semiconductor light-emitting device characterized by. 2. The p-type conductive layer includes a p-type clad layer in at least a part thereof, and the n-type conductive layer includes an n-type clad layer in at least a part thereof. The active layer contains at least one member selected from the group consisting of zinc, mercury, cadmium, magnesium and beryllium as the group II element and at least one member selected from the group consisting of sulfur, selenium and tellurium as the group VI element. The semiconductor light emitting device according to claim 1, wherein each of the semiconductor light emitting devices is formed of a II-VI group compound semiconductor containing the same. 3. The semiconductor light emitting device according to claim 2, wherein the n-type impurity is at least one selected from the group consisting of chlorine, gallium, and indium.