JP3463040B2 - Compound 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 compound semiconductor light emitting device, and more particularly, to a compound semiconductor light emitting device such as a blue light emitting diode that extends from the ultraviolet light to the visible region.

[0002]

2. Description of the Related Art Generally, II-VI compound semiconductor Zn
S, ZnSe, and the like are materials for high-efficiency light-emitting elements such as blue light-emitting diodes, which range from ultraviolet light to visible light.

FIG. 17 shows an example of a structure conventionally used in a light emitting device using this II-VI group compound semiconductor.
Shown in. In the figure, 71 is a ZnS bulk single crystal grown by the halogen chemical transport method in a molten zinc at 1000 ° C.
It is an n-type ZnS single crystal substrate which has been heat-treated for 00 hours and has low resistance. On this low resistance n-type ZnS substrate 71, a molecular beam epitaxy (MBE) method or a metal organic thermal decomposition (MO) method is used.
The light emitting layer 74 made of n-type ZnS and the insulating layer 75 made of insulating ZnS are sequentially epitaxially grown by the CVD method, and gold (Au) is vapor-deposited on the insulating layer 75 to form the positive electrode 77, thereby reducing the resistance. An ohmic electrode using indium (In) is formed on the back surface of the n-type substrate 71, and this is used as a negative electrode 78 to manufacture a MIS-type light emitting device.

[0004]

However, the structure of the conventional light emitting device described above requires a conductive substrate.
However, it is not always easy to obtain a conductive substrate in a wide-gap semiconductor such as a blue light emitting element. For example, in the above-described conventional compound light emitting device, a heat treatment step in molten zinc is required to reduce the resistance of the substrate. When a high resistance or insulating substrate is used, it is conceivable to form both positive and negative electrodes on the upper surface of the light emitting element, but in this case, there was a problem that light emission could not be effectively extracted. That is, in order to supply a current from the outside of the electrode or the light emitting element, the lead wire connected to the electrode blocks the extraction of the emitted light. In particular, in the case of a blue light emitting element, it is important to improve the extraction efficiency of emitted light because the light emitting efficiency is low.

Further, when both the positive and negative electrodes are formed on the upper surface of the light emitting element, it is necessary to expose the conductive layer below the light emitting layer. However, in a wide gap semiconductor such as a blue light emitting element, dry etching is performed. It was found that when an electrode is formed on the exposed p-type semiconductor surface, the resistance at the electrode portion becomes high. This is because it is difficult to form a good positive electrode in a wide-gap semiconductor such as a blue light emitting element, and the semiconductor surface for connecting the positive electrode needs to be formed appropriately.

The present invention has been made in view of the above points,
It is an object of the present invention to provide a compound semiconductor light emitting device having high emission efficiency of light emission and a manufacturing method in which resistance of electrodes of the compound semiconductor light emitting device is reduced.

Further, the above-described conventional structure of the light emitting device has a problem that the current is not necessarily confined in the main part including the light emitting layer, that is, the light emitting device body. This is because current leaks to the side surface of the light emitting element body. The present invention has been made in view of the above point, and is characterized in that a current is confined in the light emitting element body and a high density current is injected into the light emitting layer.

A compound semiconductor light emitting device according to the present invention has at least a first conductive type conductive layer, a light emitting layer, and a second conductive type conductive layer in this order on an insulating substrate. A compound semiconductor light emitting device having a planar structure, which has a first electrode on an exposed portion of a conductive type conductive layer and has a second electrode above the second conductive type conductive layer, wherein
The conductive layer of the mold has a high refractive index region, and the high refractive index region
Has a structure formed in a region with a smaller refractive index.
And is characterized in that it has a structure capable of taking out light emission from the light emitting layer from the light-emitting element upper ultraviolet light
Emits light in the range from to blue light .

The substrate according to the present invention has a low resistance n.
Type ZnS, low resistance n-type ZnSe or low resistance n-type Zn
Preferred examples include those made of Se _x Se _{1-x and the} like, and those made of insulating ZnS, insulating ZnSe, insulating ZnS _x Se _{1-x and the} like. Also, GaAs and G
A material such as aP or Si is also applicable.

Then, for example, a low resistance n-type ZnS substrate (or a low resistance n-type ZnSe substrate or a low resistance n-type ZnS substrate) is used.
_x Se _1-x substrate) is a ZnS bulk single crystal (or ZnSe bulk single crystal or ZnS _x Se _1-x bulk single crystal) grown by the halogen chemical transport method in molten zinc at 1000 ° C. for about 100 hours. It is preferable to use a substrate whose resistance has been reduced by heat treatment as shown below. ZnS: The resistivity (Ω · cm) is preferably 1 to 10, more preferably about 1. ZnSe: 10 ⁻² to 10 is preferable, and about 1 is more preferable. ZnS _x Se _1-x : 1 to 10 is preferable, and about 1 is more preferable. At this time, Al, Ga, etc., Cl, Br, etc. are used as n-type impurities in making each of the above-mentioned substrates, and In, I, etc. are also applicable.

Insulating ZnS [insulating ZnSe (or insulating ZnS _x Se _1-x )] is a halogen transport method,
ZnS bulk single crystal grown by sublimation method or high-pressure melting method (or ZnSe bulk single crystal or ZnS _x S
e _1-x bulk single crystal) is preferably used without being subjected to the resistance lowering treatment.

The light emitting portion in the present invention is an n-type Z
It is made of nS or n-type ZnSe. So-called ZnS
MIS type or ZnSe light emitting layer constituting a MIS type light emitting element, and a pair of n-type ZnSe and p-type ZnS
A light-emitting layer that constitutes a pn-junction light-emitting device having a monolithic device structure including a so-called planar structure, which is made of e or the like, is preferable.

In forming the conductive layer and the light emitting layer, n-type impurities include boron (B), aluminum (Al), gallium (Ga) and indium (I) which are group III elements.
n), thallium (Tl) or the like, or at least one of the Group VII elements chlorine (Cl), bromine (Br), fluorine (F), iodine (I), or the above III
A combination of at least one group element and one group VII element is used. On the other hand, as the p-type impurity, I
Group a elements lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs)
Etc., copper (Cu), silver (Ag), gold (A
u), or group III element thallium (Tl) or V
At least one of the group element nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), bismuth (Bi), or the above group Ia group, Ib group, and V group elements, and III A combination of at least one group and one group VII is used.

Next, in the present invention, the fact that the light emitting element body is substantially erected on a partial area of the substrate means that the substrate has at least the first area where the light emitting element body can be arranged and at least the light emitting element body. And a second region in which an insulating part surrounding the side surface of the substrate can be provided, which means that the light emitting element body is not provided over the entire upper surface of the substrate.

That is, the light emitting element body is, for example, 30
As shown in FIGS. 13 and 14, the diameter D1 is 30 to 100 μm with respect to the element (chip) size of 0 μm × 300 μm.
Those having a columnar structure of about m (more preferably 50 μm) are preferred.

As the insulating portion, Zn is used as a material.
An insulating layer made of a II-VI group compound semiconductor such as S, ZnSe, and ZnS _x Se _1-x can be given. CaS and CaS
e, SrS or SrSe are also applicable. Then, preferably ¹⁰ 10 ~10 ¹⁵ Ω · cm as resistivity, 10 ¹⁵ Ω · cm, more preferably, the wall thickness W of the portion in which the surrounding wall surrounding the side surface of the light-emitting element body in its insulating layer (FIG. 13) is preferably 2 to 10 μm, and 5
μm is more preferable.

Further, in the present invention, the conductive portion has an electron concentration of 10 ¹⁸ cm ^-3 or more (or a hole concentration of 10 ¹⁷ cm ^-3 ).
^-3 or more) low resistance (resistivity 10 ^-1 to 10 ^-3 Ω · c
m is preferable and 5 × 10 ⁻³ Ω · cm is more preferable)
, For example, n-type (or p-type) ZnSe layer or ZnS
_x Se _1-x layer. The light emitting portion preferably has an electron concentration of 10 ¹⁵ to 10 ¹⁸ cm ^{−3 in} the case of an n-type light emitting layer, and has a hole concentration of 10 ^{14 in} the case of a p-type light emitting layer.
-10 ¹⁷ cm ^-3 is preferable.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail based on the embodiments shown in the drawings. The present invention is not limited to this. FIG. 1 is a sectional view schematically showing a light emitting device of the first embodiment of the present invention. In the figure, 1 is a low resistance n-type ZnS substrate having a resistivity of 1 Ωcm, 2 is a first conductive layer made of low resistance n-type ZnS, and 3 is a low resistance n-type ZnS having a carrier concentration higher than that of the first conductive layer 2. Of the second conductive layer, 4 is an n-type ZnS light emitting layer, and 5 is an insulating Z
An insulating layer for hole injection made of nS, 7 is a positive electrode, and 8 is a negative electrode.

In this element, the first conductive layer 2, the light emitting layer 4, and the hole injection insulating layer 5 are single crystal semiconductor layers which are sequentially epitaxially grown on the substrate 1 by the MBE method.

The second conductive layer 3 having a carrier concentration higher than that of the first conductive layer 2 is formed during the growth of the first conductive layer 2.
A part of the surface of the growth layer is exposed to light (for example, ArF of wavelength 193 nm)
It is formed by irradiating an excimer laser beam).
That is, by growing while irradiating light, the impurity element was added to the light-irradiated portion at a high concentration, and a region having a carrier concentration higher by about one digit than that of the non-irradiated portion could be formed. The first conductive layer 2 has a thickness of 5 μm and an electron concentration of 10 ¹⁸ c
and m ^-3, and the second conductive layer 3 is formed over substantially full thickness of the first conductive layer 2, about 10 times the 10 ¹⁹ cm ^-3 about the first conductive layer 1 electron concentration using deposition of the And In this case, the resistivity of the first conductive layer 2 was 5 × 10 ⁻² Ωcm, and that of the second conductive layer 3 was 5 × 10 ⁻³ Ωcm.

At this time, the diameter d ₁ of the second conductive layer 3 is set to about 50 μm for an element (chip) size of, for example, 300 μm × 300 μm so that the current is sufficiently narrowed. The light emitting layer 4 had a thickness of 2 μm and an electron concentration of 10 ¹⁷ cm ⁻³ , and the hole injection insulating layer 5 had a thickness of 20 to 700 Å.

As the insulating layer 5 for injecting holes,
Insulating ZnS grown without adding impurities, or the above-mentioned n-type impurities and p-type impurities such as nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), etc., of group V elements are used. Stable characteristics were obtained by using insulating ZnS that was added and grown at the same time.

The positive electrode 7 was formed by vapor-depositing gold (Au) on the insulating layer 5 directly above the second conductive layer 3 by 500 to 1000 liters. The negative electrode 8 is formed of indium on the entire back surface of the substrate 1.
It is an ohmic electrode formed by applying mercury (In-Hg) and heating it in high-purity hydrogen (H ₂ ) at about 400 ° C. (30 sec).

In the above ZnSMIS type light emitting device,
The current path in the device is narrowed in the first and second conductive layers 2 and 3 into the second conductive layer 3 having a high carrier concentration and a lower resistivity, and a high-density current is injected into the light emitting layer 4. The blue light emission having a brightness of 5 to 10 times that of the conventional ZnS MIS type light emitting device was observed through the positive electrode 7, the insulating layer 5 and the end face of the device.

FIG. 2 shows the second embodiment in which the second carrier layer having a high carrier concentration is formed in a ring shape in the light emitting device of the above embodiment.
2 is a cross-sectional view schematically showing a ZnS MIS type light emitting device that is an example of FIG. In the figure, the substrate 1, the first conductive layer 2,
The light emitting layer 4 and the insulating layer 5 are the same as those of the light emitting element shown in the above embodiment, and the second conductive layer 13 is formed by irradiating ArF laser light in a ring shape when growing the first conductive layer 2. It is a ring-shaped high carrier concentration layer having an inner diameter d _{2 of} 30 μm and an outer diameter d _{3 of} 100 μm. The film thickness and carrier concentration of each layer were set to the same level as those of the light emitting device of the first embodiment. An Au vapor deposition electrode having a diameter of 30 to 100 μm is formed as the positive electrode 7 on the insulating layer 5 immediately above the second conductive layer 13, and as the negative electrode 8, In—Hg is used on the back surface of the substrate 1 to form a ring shape. An ohmic electrode was formed.

Also in this case, the current flowing in the light emitting layer 4 was confined by the second conductive layer 13, and blue light emission of high brightness was obtained. Further, since the second conductive layer 13 having a high carrier concentration has a low refractive index with respect to the first conductive layer 2,
The light generated from the light emitting portion sandwiched between the positive electrode 7 of the light emitting layer 4 and the second conductive layer 13 is surrounded by the ring-shaped second conductive layer 13 and is in the first conductive layer 2 having a higher refractive index. It could be efficiently taken out from the back surface of the substrate 1 to the outside of the device without being leaked from the end face of the device. According to the present embodiment, ZnS MIS having high brightness and high extraction efficiency
It was possible to realize a type light emitting device.

FIG. 3 is a sectional view schematically showing a light emitting device of the third embodiment according to the present invention. In the figure, 21 is an insulating ZnSe substrate, 22 is a first conductive layer made of low-resistance n-type ZnSe, 23 is a second conductive layer made of n-type ZnSe having a carrier concentration higher than that of the first conductive layer 22, and 24 is n. Type Zn
Se is a light emitting layer, 25 is a p-type ZnSe light emitting layer, 26 is a conductive layer made of low-resistance p-type ZnSe, 7 is a positive electrode, and 8 is a negative electrode.

In this device, the insulating ZnSe substrate 2
As No. 1, a ZnSe bulk single crystal grown by a halogen transport method, a sublimation method, or a high-pressure melting method is used without a resistance lowering treatment, and each semiconductor layer is sequentially epitaxially grown on this substrate 21 by the MBE method. . n-type ZnS
The conductive layers 22 and 23 and the light emitting layer 24 made of e have substantially the same shape, size, and characteristics as those of the ZnS MIS type light emitting device of Example 1, and a thickness of 2 μm made of p type ZnSe and a hole concentration of 5 × are formed thereon. Light emitting layer 25 of 10 ¹⁶ cm ^-3 , low resistance p-type ZnSe conductive layer 2 having a thickness of 5 μm and hole concentration of 5 × 10 ¹⁷ cm ^-3.
6 is formed, Au is vapor-deposited at the end of the p-type ZnSe conductive layer 26 to form the positive electrode 7, and a part of the growth layer is removed by chemical etching or reactive ion etching (RIE) to expose it. First conductive layer 22 made of n-type ZnSe
In is vapor-deposited on the negative electrode 8 to form a planar Zn structure.
The light emitting device was a Se pn junction light emitting device.

At this time, the light emitting layer 25 made of p-type ZnSe
In addition, as the p-type impurity for the conductive layer 26, Ia
Group elements lithium (Li), sodium (Na), potassium (K), group Ib copper (Cu), silver (Ag), gold (A)
u), group III element thallium (Tl), group V element nitrogen (N), phosphorus (P), arsenic (As), antimony (S)
b), bismuth (Bi), etc. were used.

By forming the positive electrode 7 at the end portion of the p-type ZnSe conductive layer 26, it was possible to minimize the interruption of light emission by the electrode and to effectively take out the light emission from the upper portion of the light emitting element. . By using a colorless and transparent insulating ZnSSe single crystal substrate grown by the sublimation method as the substrate 21, high-luminance light emission could be extracted from the substrate side.

When a wide-gap semiconductor is used as in this blue light-emitting device, the negative electrode is formed by exposing the n-type semiconductor by reactive ion etching, so that the electrode portion having low resistance is used. A highly reliable compound semiconductor light emitting device with less heat generation was obtained.

Further, by adopting the planar structure using the insulating substrate 21, it is not necessary to reduce the resistance of the substrate crystal, and the device manufacturing process is greatly simplified, and the device resistance is reduced, so that the device Low loss is possible. According to this example, a high-luminance pn junction type light emitting device could be realized.

FIG. 4 shows a schematic sectional view of a ZnSe pn junction type light emitting device which is a fourth embodiment of the present invention. The basic device structure is similar to that of the third embodiment, except that the first conductive layer 22 made of low-resistance n-type ZnSe has the first structure.
Low resistance n-type ZnSe having a carrier concentration higher than that of the conductive layer 22
A plurality of second conductive layers 33 made of is formed.

In this case, the current is confined at the position of each second conductive layer 33, and high-luminance light emission occurs. 10 μm x 10
Rectangular second conductive layer 33 having a micro dimension of about μm or more
By arranging a plurality of them in an arbitrary shape, high-luminance light emission having a shape corresponding to the arrangement of the second conductive layer 33 was obtained.

Further, FIG. 5 shows a schematic view of a fifth embodiment of the light emitting device of the present invention. In the figure, 1 is an n-type ZnS single crystal substrate. On this low resistance n-type ZnS substrate 1, a low resistance n
-Type ZnS layer and low-resistivity n-type sulfur-zinc selenide alloy (ZnS _x Se _1-x ) layer are continuously epitaxially grown, and then the n-type is formed by an etching method such as chemical etching or reactive ion etching (RIE). Z
The nS _x Se _1-x layer is removed, leaving a portion corresponding to the lower part of the light emitting portion, and a low resistance n-type ZnS layer is grown again, and an n-type Z
a first conductive layer 2 made of nS and n in the first conductive layer 2;
A second conductive layer 131 of ZnS _x Se _{1 -x} type is formed. The refractive index of ZnS is 2.4, and the refractive index of ZnS _x Se _1-x is continuous from the refractive index 2.7 of ZnS to the refractive index 2.4 of ZnSe depending on the sulfur (S) composition (x). The second conductive layer 131 has a higher refractive index than the first conductive layer 2. Further, a light emitting layer 4 made of n-type ZnS and an insulating layer 5 made of insulating ZnS are laminated on the first conductive layer 2, and an Au electrode is vapor-deposited on the insulating layer 5 to form a positive electrode 7.
Then, an In ohmic electrode is formed on the back surface of the n-type ZnS substrate 1 having a low resistance, and the negative electrode 8 is formed to be a MIS type light emitting element.

For epitaxial growth of each semiconductor layer, M
The BE method or the MOCVD method is used. That is, in each growth method, each layer could be grown with good controllability by changing the kind and amount of the raw material supplied. The ZnS insulating layer 5 can be obtained by adding no impurities. However, in the case of high resistance n-type ZnS having low insulating properties, lithium, sodium, potassium of group Ia elements which are impurities for forming p-type ZnS, Rubidium, cesium,
At least one of the group Ib elements copper, silver, gold, group III element thallium, group V element phosphorus, arsenic, antimony, and bismuth, or the above group Ia, group Ib and group V elements, and group III elements By adding a combination of at least one and
It was possible to grow nS.

Then, the first conductive layer 2 and the second conductive layer 13
1 has an electron concentration of about 10 to reduce the electric resistance of the device.
¹⁸ to 10 ¹⁹ cm ^-3 to reduce the resistivity (for example, 5 × 1
0 ^-2 ~5 × 10 ^-3 Ωcm) set. In this case, by making the resistivity of the second conductive layer 131 smaller than that of the first conductive layer 2, the current mainly flows in the second conductive layer 131, and high-density current injection occurs in the light emitting layer 4. Thus, it is possible to obtain blue light emission with high brightness. Second conductive layer 131
ZnS _x Se _1-x that forms a layer has a sulfur (S) composition (x) of 0.5 or less so that the first conductive layer 1 has a sufficiently large refractive index, and the light emitted from the light emitting layer is efficiently emitted. The thickness is set to about 10 μm so that it is well guided to the substrate side. The thickness of the first conductive layer 2 is about 2 μm so that the strain at the interface with the second conductive layer 131 is relaxed.

In order to obtain a high luminous efficiency, the light emitting layer 4 is formed of an n-type ZnS layer having a high crystallinity and having an electron concentration of about 10 ¹⁷ cm ^−3, which is lower than that of the conductive layer. ~
5 μm. The insulating layer 5 is thin in the range that maximizes the efficiency of current injection, and is set to 20 to 700 Å.

The positive electrode 7 has a thickness of 2000 to 3000 Å so that the light emitted upward from the light emitting layer is totally reflected toward the substrate, and is formed directly on the second conductive layer 131.
The negative electrode 8 is formed in a ring shape so that blue light emission can be extracted from the back surface of the substrate.

In the present embodiment, when the light emitted from the light emitting layer 4 is transmitted through the conductive layer, it is confined in the second conductive layer 131 having a high refractive index and can be efficiently extracted to the substrate side. It was possible to realize a ZnSMIS type blue light emitting device having an extraction efficiency that is an order of magnitude higher than that of a device having a conventional structure.

In this embodiment, the hole concentration is 10 ¹⁴ to 10 on the n-type ZnS light emitting layer 4 instead of the insulating layer 5.
By stacking a light emitting layer made of ¹⁷ cm ⁻³ p-type ZnS, as in the case of the above-mentioned MIS type light-emitting element, the conventional p-type
It was possible to realize a ZnSpn junction type light emitting device having an extraction efficiency that is about one digit higher than that of an n junction type or Tln junction type device.

FIG. 6 is a schematic view showing a sixth embodiment of the light emitting device according to the present invention in which the second conductive layer 131 has a convex lens shape in the ZnS MIS type light emitting device. In the figure, each layer is formed by MOCVD using light having an energy larger than the band _gap of ZnS or ZnS _x Se _{1 -x} , which is a growth layer, such as ArF having a wavelength of 193 nm.
Excimer laser light or spectral output 50 mW / nm
The growth is performed while irradiating the substrate with monochromatic light or the like which is dispersed from a xenon lamp of / cm ² . In the normal case where light is not irradiated by light irradiation, almost no growth occurs (0.0
Low growth temperature (200-350 ° C)
Also, sufficient growth can be obtained, and the growth rate can be controlled in a wide range of approximately 0.01 μm / h to 10 μm / h by the intensity of light.

Using this light irradiation growth method, first, the resistance was reduced to n.
Low resistance n-type ZnS is grown on the type ZnS substrate 1 under irradiation with light having an intensity distribution shown by the solid line A in FIG. 7, and the thickness at the central portion is about 2 μm and the thickness at the end portions is about 2 μm. Lower layer 12a of the first conductive layer having a mortar-shaped recess in the center of about 7 μm
To form. Subsequently, a low-resistance n-type ZnS _x Se _1-x is grown under irradiation of light having an intensity distribution shown by a broken line B in FIG. 7 to form a recess on the lower layer 12a of the first conductive layer. A second conductive layer 131 in the shape of a convex lens having a central thickness of about 10 μm is formed on the first conductive layer 131, and low resistance n-type ZnS is grown again under irradiation with light having an intensity distribution shown by a solid line A in FIG. The upper layer 12b of the layer is formed to be a conductive layer.

Next, on this conductive layer, an n-type ZnS light emitting layer 4,
An insulating layer 5 made of insulating ZnS is grown, a positive electrode 7 is formed on the insulating layer 5, and a negative electrode 8 is formed on the back surface of the low resistance n-type ZnS substrate 1.
To form a ZnS MIS type light emitting device.

In such a structure, the first conductive layer 12a,
Since the second conductive layer 131 having a refractive index higher than that of 12b has a convex lens shape, the light emitted from the light emitting layer 4 can be made to have a converging property and a directivity, and light emission can be performed outside the element. Could be taken out more efficiently in the direction of.

Next, FIG. 8 shows a schematic diagram of a seventh embodiment according to the present invention. In the figure, the substrate is an insulating ZnS _x Se _1-x substrate 21a using ZnS _x Se _1-x bulk single crystal grown by a halogen chemical transport method without being subjected to resistance lowering treatment. A low resistance n-type ZnS _y Se _1-y first conductive layer 32 and a low resistance n-type ZnSe
A second conductive layer 33 having a higher refractive index than the conductive layer 32 is formed. In this case, the second conductive layer 23 with respect to the first conductive layer 32
So that it has a sufficiently high refractive index, the sulfur (S) composition (y) of ZnS _y Se _1-y forming the first conductive layer 32 is 0.5.
That is all.

Next, a light emitting layer 24 made of n-type ZnSe and a light emitting layer 25 made of p-type ZnSe are formed on this conductive layer, and an ohmic electrode using Au is formed on the p-type ZnSe light-emitting layer 25 to form the positive electrode 7. Then, an ohmic electrode using In was formed on the first conductive layer 32 made of n-type ZnS _y Se _1-y exposed by removing a part of the light-emitting layer to form a negative electrode 8 and a pn-junction type light emission. As an element. In this device, the substrate has a void gap more than that of the ZnSe light emitting layer,
Since there is no reabsorption by the substrate and the planar structure is used, no electrodes are formed on the back surface of the substrate 21a, and it is possible to effectively take out light emission.

In this example, a ZnSe pn junction type light emitting device having higher extraction efficiency could be realized. Next, a schematic diagram of an eighth embodiment according to the present invention is shown in FIG. In the figure, the substrate is an insulating ZnSe substrate 21 using ZnSe bulk single crystal grown by the halogen chemical transport method without reducing the resistance. This board 21
A conductive layer 38 made of low-resistance p-type ZnSe, p-type Zn
After the Se light emitting layer 25 and the n-type ZnSe light emitting layer 24 are epitaxially grown, a low resistance n-type ZnS _y S layer having a layer thickness of 10 μm is formed.
e _1-y of the first conductive layer 32 and the first conductive layer 32
A second low resistance n-type ZnS _k Se _1-k (k <y)
P type Zn in which the conductive layer 133 is formed and the negative electrode 8 using In is exposed on the first conductive layer 32 by etching.
The positive electrode 7 using Au is formed on each of the Se conductive layers 38 to form a pn junction type light emitting element.

ZnS _y forming the first conductive layer 32
Se _1-y of sulfur (S) Composition (y) is, ZnS _k Se _1-k
The refractive index of the second conductive layer 133 formed by
Y> k + 0.5 so that it is sufficiently larger than the refractive index of 2.
And

In the present embodiment, the planar structure using the insulating ZnSe substrate 21 eliminates the need to reduce the resistance of the substrate crystal and simplifies the device manufacturing process. In addition, the negative electrode 8 is formed of low resistance n-type ZnS _y Se.
_By forming it at the end of the _1-y layer 32, it is possible to minimize the blocking of the light emission by the negative electrode 8 and to effectively take out the light emission from the upper portion of the light emitting element. Further, in the case where each lead wire for supplying a current to the light emitting element from the outside of the light emitting element is formed in the electrode, the negative electrode is most suitable for the low resistance n-type ZnS _y Se _1-y layer 32 with respect to the positive electrode. Since they are provided at the separated end positions, the lead wire could be drawn toward the outside of the light emitting element without blocking the light emitted from the upper portion of the light emitting element.

In the light emitting device of this embodiment, the negative electrode above the light emitting layer is the end farthest from the positive electrode 7 provided on the exposed portion of the conductive layer 38 made of p-type ZnSe below the light emitting layer. Since it is provided at the part position, a current flows through almost the entire light emitting layer including the vicinity of the center to emit light, so that the light emission can be effectively taken out from the upper part of the light emitting element.

Next, a schematic view of the ninth embodiment according to the present invention is shown in FIG. In the figure, the basic structure is the same as that of the ZnS MIS type light emitting device described above, but the second conductive layer 43 has a composition ratio of sulfur (S) and selenium (Se) in the thickness direction (Y direction). N-type ZnS _x (l) Se _{1 -x} (l) [l: displacement amount from the bottom surface 43a of the second conductive layer 43 in the thickness direction (Y direction)] that changes stepwise or continuously There is.

That is, the S composition [x (l)] of the second conductive layer 43 is the interface with the first conductive layer 2 (l = 0, l =
L, L: thickness of the second conductive layer 43) and x (0) = x (L)
= 1 and set to be minimum in the central portion (l = L / 2). The minimum value X (X = x (L / 2)) at this time is X <0.5 so that the second conductive layer 43 has a sufficiently high refractive index with respect to the first conductive layer 2.

Thus, the composition of the second conductive layer 43 is the first
Since ZnS changes to ZnS _x Se _1-x continuously from the interface with the conductive layer 2, it is possible to completely suppress the occurrence of defects due to the difference in the lattice constant of each layer at the interface. Also in this example, ZnS MI having high extraction efficiency
An S-type or pn-junction type light emitting device could be realized.

Next, a schematic view of the tenth embodiment according to the present invention is shown in FIG. In the figure, the basic structure is similar to that of the above-described ZnS MIS type light emitting device, but the second conductive layer 131 has a trapezoidal cross section, and the thickness of both end portions is wider than the center portion in the width direction. It is getting smaller.

In this case, after the second conductive layer 131 of the low resistance n-type ZnS _x Se _1-x layer is sequentially epitaxially grown on the low resistance n-type ZnS base 1, the low resistance n-type ZnS _x Se is formed.
_{The 1-x} layer is trapezoidally etched, and the low resistance n is again formed on it.
The type ZnS layer is epitaxially grown to form the first conductive layer 2 and the second conductive layer 131.

In such a structure, the second conductive layer 131 has a high refractive index with respect to the first conductive layer 2, and the end portion of the second conductive layer 131, that is, the first conductive layer 2 and the second conductive layer 131. In a portion where the interface of the second conductive layer 131 is inclined with respect to the light emitting layer, the incident light is refracted toward the central portion, so that the light emitted from the light emitting layer can be condensed toward the substrate side. Moreover, the extraction efficiency can be further improved. In the present embodiment, Z having higher extraction efficiency
An nS MIS type or pn junction type light emitting device could be realized.

In the light emitting elements of Examples 7, 8 and 9 as well, by making the second conductive layer a trapezoidal shape as in this example, the light emitted from the light emitting layer has a condensing property. It was possible to efficiently extract the emitted light to the outside of the device.

Further, by forming the second conductive layer 131 into a Fresnel lens structure as in the eleventh embodiment of the present invention shown in FIG. 12, a high converging property and directivity of light emitted from the light emitting layer can be obtained. Thus, it is possible to realize a light-emitting element that can emit light to the outside of the element in any direction with high efficiency.

As described above, according to the fifth to eleventh embodiments, it is possible to realize a highly efficient compound semiconductor light emitting device in which the light emission converging property, the directivity, and the extraction efficiency are significantly improved. Therefore, it is possible to provide an extremely useful light source for optoelectronics including a high-brightness blue light emitting device for information display processing.

Further, FIG. 13 shows a schematic view of a twelfth embodiment of the light emitting device of the present invention. In the figure, 1a is a ZnSe bulk single crystal grown by the halogen chemical transport method.
This is an n-type ZnSe substrate having a resistivity of about 1 Ωcm, which has been heat-treated in molten zinc at 0 ° C. for 100 hours. A mask having circular holes with a diameter of 30 to 100 μm was placed on the low resistance n-type ZnSe substrate 1a, and a conductive layer 53 made of low resistance n-type ZnSe having an electron concentration of 10 ¹⁸ cm ⁻³ or more by the MBE method and an electron concentration N-type ZnSe of about 5 × 10 ¹⁶ cm ^-3
Then, the light emitting layer 42 made of ZnSe and the hole injection insulating layer 144 made of insulating ZnSe are sequentially epitaxially grown, and the positive electrode 7 made of gold (Au) is subsequently deposited.

At this time, in the MBE method, since the raw material molecular beams have a directivity, by arranging the substrate perpendicularly to the incident direction of each raw material molecular beam, the diameter can be set at a position corresponding to the circular hole of the mask on the substrate. The main part of the columnar light emitting device having a size of 30 to 100 μm could be partially grown with good controllability.

Next, the mask is removed and the insulating ZnSe is removed.
The insulating layer 115 made of is epitaxially grown. At this time, the substrate is arranged so as to be inclined with respect to the incident direction of each molecular beam, and growth is performed while rotating the substrate to grow thickly on the side surface of the columnar structure.

After that, the excess insulating ZnSe deposited on the positive electrode 7 is removed by chemical etching or the like, and a ring-shaped ohmic electrode using In is formed as the negative electrode 8 on the back surface of the low resistance n-type ZnSe substrate 1a. The MIS type light emitting element is formed.

In the present embodiment, the current in the device is confined in the columnar main part, and it becomes possible to inject a high density current into the light emitting layer, and a ZnSe MIS type light emitting device with high brightness can be realized. did it. In addition, each semiconductor including the substrate and the light emitting layer of the light emitting device in this example is made of ZnS or a zinc-selenide alloy (ZnS _x S).
It was possible to obtain high-luminance light emission also in the MIS type light emitting device constituted by e _1-x ).

Next, a schematic diagram of a thirteenth embodiment of the present invention is shown.
14 shows. In the figure, the same low value as in the first embodiment is used.
MOCVD or MB on the resistive ZnSe substrate 1a
Electron density of 10 using E method¹⁸cm^-3From n-type ZnSe
Conductive layer 53 having an electron concentration of 10¹⁷cm^-3N-type ZnSe
And the hole concentration is 10¹⁶cm ^-3
Of the p-type ZnSe are sequentially deposited on the light emitting layer 25.
Grow.

Next, chemical etching or reactive ion is performed.
N-beam etching or the like to reduce the resistance of the growth layer.
Columnar with a diameter of 50 μm together with a part of the ZnSe substrate 1
Etching the main part of the light emitting element (light emitting element body)
After forming, insulating ZnS _xSe_1-xEpitaxial
It is grown to be the insulating layer 125. This insulating Zn
S_xSe_1-xConstitutes a main part including the light emitting layers 24 and 25.
ZnSe has a sufficiently low refractive index and a lattice constant of
The sulfur (S) composition (x) should be adjusted so that the difference does not become large.
It is set to about 0.3 to 0.7.

Next, the insulating ZnS _x Se _1-x grown on the p-type ZnSe light emitting layer 25 is removed by etching to form an ohmic electrode using Au on the exposed p-type ZnSe light emitting layer 25. N-type ZnSe with low resistance as electrode 7
An ohmic electrode using In is formed on the back surface of the substrate 1a to form the negative electrode 8 to form a pn junction type light emitting element.

In the present embodiment, it is possible to increase the current density in the light emitting layer as in the twelfth embodiment, and since the insulating layer has a lower refractive index than the main part including the light emitting layer, The light generated in the layer is confined in the main part, and the emitted light can be efficiently extracted from the substrate side. Therefore, Zn having high brightness and high extraction efficiency can be obtained.
It was possible to realize a Se pn junction type light emitting device.

In this example, ZnS _y Se _1-y (0.5>y> 0) was used for the main part including the substrate and the light emitting layer.
Then, the insulating layer is made of ZnS _z Se _1-z having an S composition (z) which is about 0.5 larger than that of ZnS _y Se _{1- y.}
An Se _1-y pn junction type light emitting device could be realized.

Next, a schematic diagram of the fourteenth embodiment of the present invention will be described.
It shows in FIG. In the figure, the substrate is a halogen chemical
ZnS grown by transfer method_xSe_1-xBulk single crystal 1
Heat treatment in molten zinc at 000 ℃ for 100 hours to reduce resistance
NSn with a resistivity of about 1 Ωcm_xSe_1-xBoard 121
And MOCVD or MBE on this substrate
Use electron density 10¹⁹cm^-3N-type ZnS_xSe_1-xConductivity
Layer 63, electron density 10 ¹⁷cm^-3Of n-type ZnSe
Light-emitting layer 24, hole concentration 10¹⁶cm^-3From p-type ZnSe
Light emitting layer 25 and 5 × 10¹⁷cm^-3The hole concentration of
P-type ZnS _xSe_1-xA conductive layer 27 of
Grow taxi.

Next, as in the thirteenth embodiment, the growth layer is etched into a columnar shape to form an insulating layer 135 made of insulative ZnS _y Se _1-y , the positive electrode 7 and I using Au.
A negative electrode 8 using n is formed to obtain a pn junction type light emitting device. At this time, the S composition (x) of ZnS _x Se _{1 -x} forming the n-type and p-type conductive layers 63 and 27 has a band gap larger than that of ZnSe forming the light emitting layers 24 and 25 by about 0.1 eV. So that x = about 0.1, the S composition (y) of ZnS _y Se _{1 -y} forming the insulating layer 135 has a sufficiently low refractive index with respect to the main part, and has a difference in lattice constant. It is set to about y = 0.3 to 0.7 so as not to increase.

In this embodiment, as in the thirteenth embodiment, current confinement and light emission confinement are possible, and the light emitting layer made of ZnSe is made of ZnS _x Se _{1-x having} a larger forbidden band width than ZnSe. Since the carrier is confined in the conductive layer and the carriers are confined in the light emitting layer, high luminous efficiency can be obtained, and Zn with high brightness and high efficiency can be obtained.
It was possible to realize a Se pn junction type light emitting device.

In this example, even when the light emitting layer was formed of ZnS _z Se ₁ -z having an S composition (z) of 0.5 or less, the S compositions of the conductive layer and the insulating layer were increased by z. Zn of high brightness and high efficiency by
It was possible to realize an SSe pn junction type light emitting device.

In the twelfth to fourteenth embodiments, since the light emitting element body is erected in a partial area and the side surface of the light emitting element body is directly covered with the insulating layer, the side surface of the light emitting element body is damaged. The leakage current that does not contribute to light emission is suppressed from occurring due to damage near the side surface of the light emitting element body or dirt attached to the side surface, that is, current confinement is realized, and the current density in the light emitting layer can be increased. It was

Next, a schematic view of the fifteenth embodiment of the present invention is shown in FIG. In the figure, reference numeral 21 denotes an insulating ZnSe substrate which is made of ZnSe bulk single crystal grown by the halogen chemical transport method without lowering the resistance. On this insulating ZnSe substrate 21, n-type Zn was formed by the same method as in the thirteenth embodiment.
After the Se conductive layer 53, the n-type ZnSe light emitting layer 24 and the p-type ZnSe light emitting layer 25 are sequentially epitaxially grown,
The growth layer is pillar-shaped etched until the n-type ZnSe conductive layer is exposed.

Next, the growth layer is further column-shaped etched together with a part of the substrate while leaving a part of the n-type ZnSe conductive layer.
Columnar main part and n-type ZnS connected to the tongue from the main part
The negative electrode forming portion 53a of the e conductive layer 53 is created.

Further, the S composition (x) is 0.3 to
An insulative ZnS _x Se _1-x having a value of about 0.7 is grown to form an insulating layer 125, and the p-type ZnSe light emitting layer 2 is formed.
5 and the insulating ZnS _x Se _1-x deposited on the tongue of the n-type ZnSe conductive layer 53 are removed by etching, and the exposed p-type ZnSe light-emitting layer 25 and the n-type ZnSe conductive layer 53 are respectively exposed. Positive electrode 7 using Au, In
The negative electrode 8 is formed by using to obtain a planar type pn junction type light emitting device.

Since the light emitting element body is erected in a partial region and the side surface of the light emitting element body is directly covered with the insulating layer, the side surface of the light emitting element body is less likely to be damaged, and the damage near the side surface of the light emitting element body is prevented. Through the dirt attached to the side,
Generation of a leak current that does not contribute to light emission was suppressed, that is, current confinement was realized, and the current density in the light emitting layer could be increased. In addition, in the light emitting element of the present embodiment, the light emitting element main body is erected in a partial region even though it is a planar type light emitting element, and the conductive layer surface between the positive and negative electrodes including the side surface thereof is Since it is covered with the insulating film, leakage current that does not contribute to light emission is suppressed through damage near the positive and negative electrodes and dirt attached to the conductive layer between the positive and negative electrodes. It was realized and the current density in the light emitting layer could be increased.

As described above, according to the twelfth to fifteenth embodiments, it is possible to realize a compound semiconductor light emitting device including blue light emission having high brightness and high external efficiency, and can be used in various display devices, printers, facsimiles and the like. It is extremely useful as a light source of high energy and high brightness.

[0081]

Since the present invention is configured as described above, it is possible to suppress the generation of a current that does not pass through the light emitting layer, that is, a so-called leak current, through an adhered substance or the like attached to the compound semiconductor light emitting device. Further, since the light emitting element body is erected on a part of the substrate or on the conductive layer of the first conductivity type, the light emitting element body is not damaged in a dicing process for separating the wafer from the elements. You can

[Brief description of drawings]

FIG. 1 is a configuration explanatory view showing a first embodiment of the invention.

FIG. 2 is a structural explanatory view showing a second embodiment of the invention.

FIG. 3 is a structural explanatory view showing a third embodiment of the invention.

FIG. 4 is a structural explanatory view showing a fourth embodiment of the invention.

FIG. 5 is a structural explanatory view showing a fifth embodiment of the invention.

FIG. 6 is a structural explanatory view showing a sixth embodiment of the invention.

FIG. 7 is a schematic diagram showing an intensity distribution of irradiation light in light irradiation growth used in manufacturing the light emitting device of the sixth embodiment.

FIG. 8 is a structural explanatory view showing a seventh embodiment of the invention.

FIG. 9 is a structural explanatory view showing an eighth embodiment of the invention.

FIG. 10 is a structural explanatory view showing a ninth embodiment of the invention.

FIG. 11 is a structural explanatory view showing a tenth embodiment of the invention.

FIG. 12 is a structural explanatory view showing an eleventh embodiment of the invention.

FIG. 13 is a structural explanatory view showing a twelfth embodiment of the invention.

FIG. 14 is a structural explanatory view showing a thirteenth embodiment of the invention.

FIG. 15 is a structural explanatory view showing a fourteenth embodiment of the invention.

FIG. 16 is a structural explanatory view showing a fifteenth embodiment of the invention.

FIG. 17 is a structural explanatory view showing a conventional example.

[Explanation of symbols]

1, 71 low resistance n-type ZnS substrate 1a low resistance n-type ZnSe substrate 2 n-type ZnS first conductive layer 3, 13 n-type ZnS second conductive layer 4, 74 n-type ZnS light emitting layer 5, 75 ZnS insulating layer 7, 77 Positive electrode 8, 78 Negative electrode 12a Lower layer part 12b of n-type ZnS first conductive layer Upper layer part 21 of n-type ZnS first conductive layer Insulating ZnSe substrate 21a Insulating ZnS _x Se _1-x substrate 22 n-type ZnSe First conductive layer 23 n-type ZnSe second conductive layer 24 n-type ZnSe light emitting layer 25 p-type ZnSe light-emitting layer 26, 38 p-type ZnSe conductive layer 27 p-type ZnS _x Se _1-x conductive layer 32 n-type ZnS _y Se _{1 -y} first conductive layer 33 n-type ZnSe second conductive layer 42 n-type ZnSe light emitting layer 43 n-type ZnS _x (l) Se _1-x (l) second conductive layer 53 n-type ZnSe conductive layer 63 n-type ZnS _x Se _1-x conductive layer 115 ZnSe insulation Layer 121 Low-resistance n-type ZnS _x Se _1-x substrate 125 ZnS _x Se _1-x insulating layer 131 n-type ZnS _x Se _1-x second conductive layer 133 n-type ZnS _k Se _1-k second conductive layer 135 ZnS _y Se _1-y insulating layer 144 ZnSe hole activation insulating layer

Continued front page       (56) References JP-A-63-18680 (JP, A)                 Japanese Patent Laid-Open No. 50-153883 (JP, A)                 JP-A-49-19782 (JP, A)

Claims (3)

(57) [Claims] 1. An insulating substrate having at least a conductive layer of a first conductivity type, a light emitting layer, and a conductive layer of a second conductivity type in this order, and exposing the conductive layer of the first conductivity type. A compound semiconductor light emitting device having a planar structure, which has a first electrode in a portion thereof and a second electrode above the second conductive type conductive layer , wherein the second conductive type conductive layer has a high refractive index. Rate area,
The refractive index region is formed in the region of lower refractive index.
Structure has, blue light from ultraviolet light, characterized in that it has a configuration that can obtain luminescence from the luminescent layer from the light-emitting element upper
A compound semiconductor light emitting device which emits light in the range of . 2. The resistivity of the conductive layer of the first conductivity type is 1
It is 0 ⁻¹ to 10 ⁻³ Ω · cm, and
The compound semiconductor light-emitting device according to. 3. The second electrode is arranged at an end portion most distant from the first electrode.
The compound semiconductor light-emitting device according to.