JPH0945959A - Light emitting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an LED having a Bragg multilayer reflection film in which the forward voltage drop is suppressed while enhancing the efficiency, luminance and purity of wavelength. SOLUTION: In an LED having a Bragg semiconductor multilayer reflection film 12 sandwiched between pn junction emission layer 13, 14, 15 of double heterostructure and a semiconductor substrate 10, the structure is contrived to feed the pn junction emission layer 13, 14, 15 with a current not through a multilayer reflection film 12. For example, a trench is made from the surface down to a specific depth and one electrode 18 of LED is disposed on the bottom 17 of the trench.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a semiconductor light emitting device. Specifically, it relates to a semiconductor light emitting device such as a light emitting diode having a Bragg-type multilayer reflective film.

[0002]

2. Description of the Related Art Semiconductor light emitting diodes (LEDs) are known as products having various colors and luminances by selecting a semiconductor material and its structure. These semiconductor LEDs
Is generally produced by epitaxially growing a high-quality single crystal on a semiconductor single crystal substrate in order to prevent generation of defective products due to defects of the substrate. In these LEDs, electrons and holes are recombined by a pn junction formed as a multilayer structure by epitaxial growth to emit light. The pn junction is generally formed by doping p-type and n-type impurities during the epitaxial growth or after the crystal growth. Usually, the current path is formed on each surface of the multilayer structure formed on the substrate surface. Is a vertical direction,
The electrodes are divided into a front surface side and a back surface side with the pn junction layer in between, and are provided so as to face each other. Regarding brightness, which is one of the important characteristics of LEDs, attempts have been made to efficiently extract light from one direction using a so-called Bragg-type multilayer reflective film in order to obtain a product with even higher brightness.
Further, due to the pn junction, in order to emit light more efficiently, a hetero structure is provided on both sides of the active layer, and a double hetero (DH) structure in which electrons and holes are confined in the active layer is adopted.

FIG. 5 shows an example of the structure of an AlGaInP double heterostructure LED having a conventional Bragg-type multilayer reflection film (for example, a high efficiency InGaAIP green color-developing diode; 1991 International Conference of Solid-Stay). Toe Device and Material Extended Abstract, Yokohama, Hi
gh-Efficiency InGaAlP Green Light-Emitting Diode;
Extended Abstract of the 1991 International Confere
nce on Solid State Device and Materials, Yokohama,
1991 p741-742). The LED shown in FIG.
-N-GaAs buffer layer 3 on the -GaAs substrate 30
1, Bragg-type multilayer reflective film 32, n- (Al _x G
a1 _-x ) _0.5 In _0.5 P cladding layer 33, undoped-
_{(Al y Ga 1-y)} 0.5 In 0.5 P active layer 34, p-
(Al _x Ga _1-x ) _0.5 In _0.5 P clad layer 35, p
-A GaAs cap layer 36 is sequentially stacked to form p-GaA.
A p-type electrode 38 is formed on the s cap layer 36, and n−
An n-type electrode is formed under the GaAs substrate 30. With such a structure, the emitted light is reflected by the semiconductor multilayer reflective film 32 and is effectively extracted from the p-AlGaInP clad layer 35 side on the front surface side without being absorbed by the n-GaAs substrate on the rear surface side. . When the emission wavelength of the LED is λ and the refractive index is n, this semiconductor multilayer film 32
Constitutes a Bragg reflection film in which a λ / 4n film having a high refractive index and a λ / 4n film having a low refractive index are formed in multiple layers. Here, the high refractive index film is n- (Al _z Ga _1-z ) _0.5 In _0.5 P (0
≦ z <1), the low refractive index film is n-Al _0.5 In _0.5 P
It is. With such a structure, it is possible to form a reflective film having a high reflectance in the emission wavelength region. Light emitted from the active layer and traveling toward the substrate is reflected by the multilayer reflective film and emitted from the upper surface of the element, so that the light extraction efficiency can be improved. The p-
_{(Al x Ga 1-x)} 0.5 In 0.5 P on the surface of the cladding layer 35, to improve the light extraction efficiency, p-type electrode 38 is a metal electrode through the p-GaAs cap layer 16 only in a part of Are formed.

[0004]

As shown in FIG. 5, the multilayer reflective film 32 is made of n- (Al _x Ga _1-, which forms a DH structure.
_x ) _0.5 In _0.5 P clad layer 33 and GaAs substrate 30
Although it is possible to realize high light extraction efficiency by disposing the multi-layered reflective film 32 between them, there is a new problem that the element resistance increases due to the provision of the multilayer reflective film 32. Since the AlGaInP-based material used for the multilayer reflective film has a large band offset of the valence band at the junction interface between the high refractive index film and the low refractive index film, it is particularly useful when a p-type multilayer reflective film is formed. However, there is a drawback in that holes cannot be easily injected and the device resistance is significantly increased.
This increase in element resistance leads to an increase in forward voltage,
There is a drawback that the device characteristics such as an increase in power consumption and heat generation are adversely affected. For example, diode current 20mA
, The forward voltage was increased by about 0.1V. Further, in recent years, GaAs has been used as a high-refractive index film in order to obtain a higher reflectance, and the band offset at each heterojunction interface forming the multilayer reflection film is further increased. The increase in resistance is becoming noticeable. Also, the AlGaIn shown in FIG.
In a PLED, in order to obtain a yellow or green emission color, as the Al composition of the light emitting layer is increased, the height of the hetero barrier with the cladding layer becomes smaller, and carriers easily overflow.
Infrared emission in the s buffer layer became a problem. When such an element is used for a communication optical fiber, which has been attracting attention in recent years, there is little problem because only a specific wavelength region with less loss is selectively transmitted in a long distance, but this infrared component is
The yellow light emitting LED may reach 50% of the total light emission amount, and in short-distance communication, even the infrared light emission component is transmitted, and the total light reception amount becomes too large, which may cause a malfunction. was there.

The present invention has been made in view of the above points, and has a DH structure LED provided with a Bragg type multilayer reflective film.
In the light emitting element having an electrode structure for current injection for avoiding an increase in element resistance due to the multilayer reflective film and an increase in forward voltage, and an infrared ray, while taking advantage of the advantage of improving the light extraction efficiency. The present invention provides a light emitting device having a current injection electrode structure for preventing light emission.

[0006]

In order to achieve the above object, a light emitting device according to the present invention is provided on a semiconductor substrate 10, 20 and an upper portion of the semiconductor substrate 10, 20 as shown in FIG. 1 or 2. Bragg-type semiconductor multilayer reflective film 12 (hereinafter referred to as a reflective film), and p provided on the reflective film 12.
The light emitting layers 13, 14, 15 made of an n-junction, and the first metal electrode 18 and the second metal electrode 1 for applying a predetermined current to the light emitting layers 13, 14, 15 made of a pn junction.
9 is a light-emitting element such as an LED that has both 9 and p,
The main current path is selected so that the main current applied to the n-junction flows without passing through the reflective film 12, and the first metal electrode 18 and the second metal electrode are arranged. (Refer to claim 1).

Preferably, as shown in FIG. 1 or 2, p
The n-junction light emitting layer is a light emitting layer including at least a first conductivity type first semiconductor region 13 and a second conductivity type second semiconductor region 15, and the first semiconductor region 13 is a reflective film. 12, the second semiconductor region 15 is formed on the first semiconductor region 13 and forms a pn junction, and the first metal electrode 18 is formed on the second semiconductor region 15 from the upper side. That is, the second metal electrode 19 is formed on the bottom of the groove that penetrates the second semiconductor region 15 and reaches the first semiconductor region 13, and the second metal electrode 19 is formed on the upper part of the second semiconductor region 15. (See item 2). That is, the first metal electrode 18 and the second metal electrode 19 are both taken out from the same main surface. Here, the first conductivity type means, for example, n
Type conductivity type, and the second conductivity type means a p-type conductivity type opposite to the first conductivity type. In this case, the first metal electrode 18 is an n-type ohmic electrode, and the second metal electrode 19 is
Means a p-type ohmic electrode. However,
Of course, the conductivity types may be reversed, and the first conductivity type may be p-type and the second conductivity type may be n-type.

More preferably, as shown in FIG. 1 or 2, buffer layers 11, 21 of the first conductivity type are formed between the reflective film 12 and the semiconductor substrates 10, 20 (see claim 3). Alternatively, the second conductive type cap layer 16 is formed between the second semiconductor region 15 and the second metal electrode 19 (see claim 4).

In the structure of the first feature of the present invention, more preferably, the light emitting layer composed of the pn junction is a first clad layer 13 of a first conductivity type and a second clad layer of a second conductivity type. 15 and a double heterojunction (DH) structure including an undoped active layer 14 sandwiched between the first and second cladding layers (see claim 5).
In this DH structure, the cladding layer is typically (Al _x G
a _1-x) is _0.5 an In _0.5 P layer, the active layer (Al _y G
a _1-y ) _0.5 In _0.5 P layer (see claim 6), n
A structure in which an undoped active layer 14 is sandwiched between a type clad layer, an n type clad layer 13, and a p type clad layer 15. The composition x of AI of the clad layer is preferably about 0.7 <x <1.
The composition y is preferably 0 <y <0.6. The DH structure may be another DH structure such as an AlGaAs type. Here, “undoped” means that impurities are not intentionally doped, and there may be residual impurities of about 1 × 10 ¹⁴ to 2 × 10 ¹⁶ cm ⁻³ .

More preferably, as shown in FIG. 2, the semiconductor substrate is a semi-insulating GaAs substrate 20.

The second feature of the present invention is as shown in FIG.
The semiconductor substrate 10, the reflection film 12 provided on the semiconductor substrate 10, the light emitting layers 13, 14 and 15 provided on the reflection film 12 and having the pn junction, and the light emitting layer 13 having the pn junction, A light emitting element such as an LED having at least a first metal electrode 18 and a second metal electrode 19 for applying a predetermined current to the electrodes 14 and 15, and a light emitting layer formed of a pn junction has a first conductivity type. First semiconductor region 13
And a second semiconductor region 15 of the second conductivity type, the first semiconductor region 13 is formed on the reflective layer 12, and the second semiconductor region 15 is the first semiconductor region 13.
The first metal electrode 18 formed on the upper surface of the semiconductor substrate 10 penetrates the reflective layer from the back surface of the semiconductor substrate 10,
3 formed on the bottom of the groove reaching the second metal electrode 19
Means that the main current path is formed so that the main current applied to the pn junction flows through the second semiconductor region 15 without passing through the reflective film 12 (see claim 8). .

[0012] Preferably, the light emitting layer comprising a pn junction is
By including the first conductivity type first cladding layer 13, the second conductivity type second cladding layer 15, and the undoped active layer 14 sandwiched between the first and second cladding layers. is there.

As shown in FIG. 4, the third feature of the present invention is that the semiconductor substrate 10, the reflecting film 12 provided on the semiconductor substrate 10, and the pn provided on the reflecting film 12 are provided.
The light emitting layers 13, 14, 15 made of junctions, and the first metal electrode 18 and the second metal electrode 19 for applying a predetermined current to the light emitting layers 13, 14, 15 made of the pn junction.
A light emitting element such as an LED including at least
The light emitting layer formed of an n-junction includes at least a first semiconductor region 13 of the first conductivity type and a second semiconductor region 15 of the second conductivity type, and the first semiconductor region 13 is formed on the reflective layer 12. The second semiconductor region 15 is formed on the first semiconductor region 13 and the first metal electrode 18 is formed so as to penetrate a part of the reflective film 12.
The second metal electrode 19 is formed on the back surface of the semiconductor substrate 10 so as to be electrically connected to the first semiconductor region 13 via a short circuit 45 region that electrically short-circuits the semiconductor substrate 10 with the second metal electrode 19. Pn formed on the second semiconductor region 15
That is, the main current path is selected so that the main current applied to the junction flows without passing through the reflection film 12 (see claim 9). An electrical short circuit means that the voltage drop between them is an LED
Is to be electrically connected so as to have a small resistance value that does not affect the forward voltage drop.

Preferably, the light emitting layer comprising a pn junction is
By including the first conductivity type first cladding layer 13, the second conductivity type second cladding layer 15, and the undoped active layer 14 sandwiched between the first and second cladding layers. is there.

Preferably, as shown in FIG. 4, the short circuit area 4
That is, the insulating region 44 is provided on the upper part of 5 (claim 1
0). A void (air gap) may be used as the insulating region 44.

According to the above-mentioned features of the present invention, in the light emitting device having the pn junction light emitting layer having the DH structure or the like on the Bragg type semiconductor multilayer reflection film 12, the p type for injecting current into the pn junction light emitting layer. Either the electrode or the n-type electrode is on the multilayer reflective film 12 or the multilayer reflective film 1
2 is formed on a layer (for example, a clad layer) which is in contact with 2, and the other electrode is formed on the layer opposite to the layer which is in contact with the multilayer reflective film among the layers constituting the pn junction light emitting layer. The current can be injected into the light emitting layer without the current passing through 12. Therefore, according to the structure of the present invention, it is possible to avoid an increase in element resistance due to the multilayer reflective film, and thus an increase in forward voltage, and at the same time, it is possible to take advantage of an improvement in light extraction efficiency. Further, according to the feature of the present invention, the carriers overflowing from the DH structure provided on the semiconductor multilayer film structure pass through the semiconductor multilayer film, reach the semiconductor substrate side, and emit infrared light in the GaAs buffer layer or the like. Things are gone.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The details of the present invention will be described below with reference to the embodiments shown in the following drawings. FIG. 1 shows the first embodiment of the present invention.
DH type LED having a multilayer reflective film according to the embodiment
The structure is shown. In FIG. 1, a thickness λ / 4 is formed on an n-GaAs substrate 10 with an n-GaAs buffer layer 11 interposed therebetween.
n- (Al _0.5 Ga _0.5 ) _0.5 In
_A Bragg-type semiconductor multilayer reflective film 12 having a periodic structure of _0.5 P and a low refractive index film n-Al _0.5 In _0.5 P is formed. On top of this, n-Al _0.5 In _0.5 P clad layer 1
3, an undoped (Al _0.45 Ga _0.55 ) _0.5 In _0.5 P active layer 14, a p-Al _0.5 In _0.5 P clad layer 15 are formed into a DH structure, and a p layer is formed on the DH structure.
-A GaAs cap layer 16 is formed. As shown in FIG. 1, the p-GaAs cap layer 16 has p-Al _0.5 I.
A p-type electrode 19 made of an AuZn alloy is formed only on a part of the n _0.5 P clad layer 15, and on this p-GaAs cap layer 16. p-Al _0.5 I
n _0.5 P cladding layer 15, undoped (Al _0.45 Ga
_0.55 ) _0.5 In _0.5 P penetrates the active layer 14 and
_At the bottom of the groove reaching the _0.5 In _0.5 P clad layer 13, A
The n-type electrode 18 made of uGe alloy is p-Al _0.5 In
It is formed so as to be electrically connected to the _0.5 P cladding layer 13. Although not shown, in the element shown in FIG. 1, a lead frame is mounted on a predetermined stem or frame with a conductive adhesive on the n-GaAs substrate 10 side downward, and wire-bonded to the n-electrode 18 and the p-electrode 19. Or by connecting the n-electrode 18 directly to the frame with a conductive adhesive to enable electrical connection with an external circuit. Alternatively, the element shown in FIG. 1 may be monolithically integrated with another switching element. In the structure shown in FIG. 1, since the n electrode 18 and the p electrode 19 which are ohmic contact metal electrodes are on the same surface side, monolithicization is easy.

In FIG. 1, the Bragg type multilayer reflection film is L
For the emission wavelength λ of the ED, a high-refractive index film having a film thickness of λ / 4n and a low-refractive index film having a film thickness of λ / 4n may be stacked, for example, 20 cycles. The reflectance of the multilayer reflective film is 90% or more in about 10 cycles, so that 10 cycles of lamination may be used. The n-Al _0.5 In _0.5 P cladding layer 13 is Si-doped and has an impurity density of 4 × 10 ¹⁷ cm ⁻³ .
The undoped (Al _0.45 Ga _0.55 ) _0.5 In _0.5 P active layer 14 has an impurity density of 1 × 10 ¹⁵ to 1 × 10 ¹⁶ cm ^-3 and a thickness of 0 × 10 ¹⁸ cm ⁻³ and a thickness of _0.3 to 1 μm. .2-
0.6 μm, p-Al _0.5 In _0.5 P clad layer 1
5 is Zn-doped and has an impurity density of 4 × 10 ¹⁷ to 1 × 10 ^18.
cm ^-3, and a thickness of 0.5 to 1 [mu] m, p-GaAs cap layer 16 may be a thick 10nm~50nm in impurity concentration ^{1 × 10 18 ~1 × 10 19} cm -3. The cladding layers 13 and 15 in the first embodiment of the present invention are more generally (AI _x Ga _1-x ) _0.5 In _0.5 P layers (0.
7 <x <1 and the active layer 14 may be (AI _y Ga).
_It may be a _1-y ) _0.5 In _0.5 P layer (0 <y <0.6).

In the structure of FIG. 1, current is injected into the light emitting layer without passing through the semiconductor multi-layer reflective film 12, so that a low element resistance equivalent to that of an element without the semiconductor multi-layer reflective film can be obtained.
The forward voltage of the ED is reduced, and heat generation and power consumption are significantly reduced. Further, the carriers overflowing from the DH structure provided on the semiconductor multilayer reflective film structure by the structure of FIG. 1 pass through the semiconductor multilayer reflective film, reach the GaAs buffer layer 11, and do not emit infrared light.

In order to further reduce the forward drop voltage, 5 × 10 ¹⁸ cm ⁻³ to 2 × 1 is formed below the n-type electrode 18.
An n ⁺ contact region of about 0 ¹⁹ cm ⁻³ may be formed if necessary (the n ⁺ contact region is not shown).

The DH structure LED shown in the first embodiment of the present invention can be manufactured by the following manufacturing method.

(A) First, metal organic chemical vapor deposition (MOC)
VD method), CBE (Chemical Beam Ep)
Itaxy) method, MBE (Molecular BEA)
m Epitaxy method, ALE (Atomic Lay)
er Epitaxy) method or MLE (Molec)
The n-GaAs buffer layer 11 and n- (Al _0.5 Ga) are formed on the n-GaAs substrate 10 by using an epitaxial growth technique such as a U.S.A.
_0.5 ) _0.5 In _0.5 P / n-Al _0.5 In _0.5 P multilayer reflective film 12, n-Al _0.5 In _0.5 P clad layer 13, undoped (Al _0.45 Ga _0.55 ) _0.5 In _0.5 P active layer 1
4, p-Al _0.5 In _0.5 P clad layer 15, p-Ga
Multilayer continuous epitaxial growth of the As cap layer 16 is performed. As the n-GaAs substrate 1, for example, a Si-doped (100) plane 2 to 30 ° off substrate may be used.

The MOCVD method may be atmospheric pressure MOCVD or low pressure MOCVD, but preferably, low pressure MOCVD method, particularly vertical type low pressure MOCVD method. Triethyl gallium (T
EG), TMAAI (trimethylamine alane), TM
AI (trimethylaluminum), trimethylindium (TMI), or the like is used as a group V source gas such as phosphine (PH ₃ ) or arsine (AsH ₃ ). Or tertiary butyl phosphine (((C ₄ H
₉ ) PH ₂ ; TBP), tertiary butyl arsine ((C ₄ H ₉ ) AsH ₂ ; TBA) and the like may be used. As the n-type dopant gas, monosilane (Si
H ₄ ), disilane (Si ₂ H ₆ ), diethyl selenium (DESe), diethyl tellurium (DETe) or the like may be used, but monosilane is preferable. Diethylzinc (DEZn) or trimethylgallium (TMG) may be used as the p-type dopant gas. These raw material gas and dopant gas are introduced into a reaction tube controlled to a reduced pressure of 5 kPa to 10 kPa using a mass flow controller or the like. The ratio of the group V source gas to the group III source gas, the so-called V / III ratio, is, for example, 120 to 17.
It may be performed at about 0. The substrate temperature during growth is, for example, 65
It may be performed at about 0 ° C to 700 ° C. Alternatively, when growing by the CBE method, at a substrate temperature of 520 ° C. under a pressure of 1.3 × 10 ⁻³ Pa, TEG and AsH ₃ are introduced and n-GaA is introduced.
The s buffer layer 11 and the p-GaAs cap layer 16 are grown, and TEG, TMAI, and T are formed at a substrate temperature of 480 to 520 ° C.
N- (Al _0.5 Ga _0.5 ) _0.5 In by MI and PH _3
0.5 P layer is grown, and then TMAI, TMI and PH _{3 are} added.
And n-Al _0.5 In _0.5 P layer of the multilayer reflective film, n-
The Al _0.5 In _0.5 P clad layer 13 and the like may be grown.

If the source gas used in the CBE method is alternately introduced and the exchange surface reaction on the semiconductor substrate is used, MLE is used.
It becomes law. For example, substrate temperature 480 ° C, pressure 6 × 10 ^-4
Introduced TEG for 4 seconds at Pa, evacuated for 3 seconds, As
Since one molecular layer of GaAs can be grown by a series of gas introduction 1 cycle of introducing H ₃ for 20 seconds and then evacuating for 3 seconds, the laminated wafer of FIG. 1 has a structure with an accuracy of a molecular layer according to the MLE method. . In particular, the multilayer reflective film 12 is set to λ / 4
The MLE method is preferable when the layer is precisely controlled with the thickness of n. Also, depending on the thickness and accuracy of the thickness,
The MLE method and the MOCVD method (or the CBE method) may be combined and grown.

(B) Next, the wafer having a multilayer structure thus continuously epitaxially grown is taken out from the reaction tube, a predetermined portion is covered with a photoresist (hereinafter referred to as a resist) by photolithography, and the other portion is covered.
The p-GaAs cap layer 16 was etched with a sulfuric acid-based etching solution, the p-AI _0.5 In _0.5 P clad layer 15 was subsequently etched with hot phosphoric acid, and the photoresist was used as a mask to undoped the Br-type etching solution. (AI _0.45 Ga _0.55 ) _0.5 In _0.5 P The active layer 14 is removed by etching, and n-Al _0.5 In _{0.5 is} again added with hot phosphoric acid.
The P clad layer 13 is continuously etched so as to leave a part thereof. Alternatively, this etching is performed using n-AI _0.5 In
You may carry out until it reaches a multilayer reflective film, without leaving a part of _0.5 P clad layer 13.

The p-GaAs cap layer 16,
The resist used for etching the p-Al _0.5 In _0.5 P clad layer 15, the undoped (Al _0.45 Ga _0.55 ) _0.5 In _0.5 P active layer 14, and the n-Al _0.5 In _0.5 P clad layer 13 was removed, and the bottom of the groove was removed. An n-type electrode 18 which is a metal electrode forming an ohmic contact is formed.
The so-called lift-off method may be used to form the n-type electrode 18. That is, a resist is applied to the entire surface for lift-off, a predetermined resist pattern is formed on a portion other than the portion where the n-type electrode 18 is to be formed by photolithography, and an AuGe film is deposited thereon by vacuum vapor deposition or sputtering. For example, A with a thickness of 200 nm to 1 μm
A u-Ge (12 wt%) film is formed by the EB vapor deposition method.
Then, if the resist is removed, the n-type electrode 18 having the shape shown in FIG. 1 is formed. Without using the lift-off method,
The same pattern can be obtained by etching with a predetermined etchant such as a halogen / halogenated salt-based etchant such as a KI / I ₂ solution or a cyan-based etchant by ordinary photolithography, but the lift-off method is simpler. . Thereafter, sintering of the electrodes is performed at 360 to 450 ° C. in an H ₂ atmosphere or an inert gas atmosphere such as N ₂ . Sintering at 360 ° C. for about 2 seconds is preferable. It should be noted that 5 × 10 ¹⁸ to 2 × 10 ¹⁹ is formed below the n-type electrode 18 by using an ion implantation method or a selective epitaxial growth method.
It is preferable to form an n ⁺ -AI _0.5 In _0.5 P contact region of about cm ⁻³ and then deposit an Au—Ge film or the like because the contact resistance can be reduced.

(C) Similarly, after the n-type electrode 18 is formed, as shown in FIG.
As shown in FIG. 3, the AuZn electrode 1 as a p-type ohmic metal electrode is provided only at a predetermined position of the p-GaAs cap layer 16.
9 is formed. The AuZn electrode is also patterned by AuG
Lift-off method or halogen /
It may be carried out using a predetermined etchant such as a halide salt type. Thereafter, sintering of the AuZn electrode 19 is performed at 360 to 450 ° C. in an H ₂ atmosphere or an inert gas atmosphere such as N ₂ . Then, using this AuZn electrode 19 as a mask, except the lower part of the AuZn electrode 19, p-GaA
By etching the s cap layer 16, the DH type LED shown in FIG. 1 is completed.

(D) After that, the LED of FIG. 1 is mounted on a lead frame with a conductive adhesive with the n-GaAs substrate 10 side facing down, and is wire-bonded by using an Au wire or the like, or conductive. Connect directly to the frame with adhesive.

With the above manufacturing method, the DH type LED of the first embodiment of the present invention can be manufactured easily and with a high yield. Moreover, since no current flows to the n-GaAs substrate side, there is no deterioration due to the imperfections of the crystal of the GaAs substrate 1, so that a long-life LED can be manufactured with high productivity. Also, the mounting and bonding steps are easy because the electrodes are on the front surface side. In addition, although an L-shaped groove with one side cut off is shown in FIG. 1, n-Al _0.5 In
_The groove may have any shape as long as it can supply current to the _0.5 P cladding layer 13. That is, it may be a U-shaped groove, a V-shaped groove, or an inverted mesa-shaped groove.

FIG. 2 shows a D according to the second embodiment of the present invention.
The cross-sectional structure of H type LED is shown. Since the present invention is characterized in that no current is passed to the substrate side, the substrate does not have to be an n-GaAs substrate as in the first embodiment of the present invention. An insulating GaAs substrate 20 is used. As a semi-insulating GaAs substrate, undoped or In-doped liquid sealing pulling method (L
An EC) substrate, an optimal As pressure applied CZ substrate (PCZ substrate), or a Cr—O-doped semi-insulating GaAs substrate may be used. A PCZ substrate with a dislocation density of 1000 cm ^-2 or less is preferably used. A high-resistance GaAs buffer layer 2 having a thickness of 0.5 to 7 μm on a semi-insulating GaAs substrate 20.
1 is formed, and a Bragg-type semiconductor multilayer reflective film 2 is formed thereon.
2 is formed on the n-Al _0.5 In _0.5 P clad layer 23 and undoped (Al _0.45 Ga _0.55 ) _0.5 In.
_A DH structure including a _0.5 P active layer 24 and a p-Al _0.5 In _0.5 P clad layer is formed, and a p-type electrode 19 is formed via a p-GaAs cap layer 16.

The Bragg-type semiconductor multilayer reflective film 22 of the second embodiment of the present invention has a thickness of λ / 4 as a high refractive index film.
n-GaAs film and a low-refractive-index film made of a high-resistance Al _0.5 In _0.5 P film having a thickness of λ / 4n.
It is constructed by stacking for ~ 30 cycles. In addition, n-Al _0.5 In
_{The 0.5} P clad layer 23 is Si-doped and has an impurity density of 4 × 1.
0 ¹⁷ cm ⁻³ to 1 × 10 ¹⁸ cm ⁻³ , thickness 0.3 to 1 μm, undoped (Al _0.45 Ga _0.55 ) _0.5 In _0.5 P active layer 24 has an impurity density of 1 × 10 ¹⁵ to 1 × 10 ¹⁶ cm. ^-3 ,
Thickness is 0.2-0.6 μm, p-Al _0.5 In _0.5 P
The cladding layer 25 is Zn-doped and has an impurity density of 4 × 10 ¹⁷
˜1 × 10 ¹⁸ cm ⁻³ and thickness 0.5 to 1 μm.

Similar to the first embodiment of the present invention, partially using a sulfuric acid-based, hot phosphoric acid-based, and Br-based etching solution,
Etching is performed until a part of the p-Al _0.5 In _0.5 P clad layer 15 is left or until reaching the multilayer reflection film to form a groove portion as shown in FIG. 2, and an n-type is formed on the etching surface 27 at the bottom of the groove portion. An AuGe electrode is formed as the electrode 18. The p-GaAs cap layer 16 is removed by etching except the lower part of the p-type electrode 19 of AuZn.
The light can be extracted more efficiently. Although not shown, the DH type LED having the cross-sectional structure of FIG. 2 is mounted on the lead frame with a conductive adhesive on the substrate side downward, and further wire bonded to the n-electrode 18 and the p-electrode 19 according to the present invention. The structure of the light emitting device is assembled. The n-electrode 18 may be directly connected to the frame with a conductive adhesive.

Similar to the first embodiment of the present invention, the semiconductor multiple reflection film 22, the layers 23, 24, 25, etc. of the DH structure are formed by MOCVD, CBE, MBE, ALE, MLE or the like. It may be continuously deposited by epitaxial growth.

According to the second embodiment of the present invention shown in FIG. 2, GaAs-AlIn having a large band offset.
Even when the P semiconductor multilayer film is provided, the element resistance can be as low as that of the element without the semiconductor multilayer film, and the forward voltage is lowered. In addition, carriers overflowing from the double hetero structure provided on the semiconductor multilayer film structure,
It does not pass through the semiconductor multilayer film, reaches the GaAs layer, and emits infrared light. Furthermore, since no current flows through the substrate, it is possible to prevent deterioration due to defects in the substrate. Since the structure of FIG. 2 uses the semi-insulating GaAs substrate 20, when an optical integrated circuit (optical IC) is formed,
The elements can be easily separated, and since the n-type electrode 18 and the P-type electrode 19 are on the same surface side, wiring at the time of integration is also easy.

In the above-described first and second embodiments of the present invention, the step shape provided on the front surface side has been basically described, but a current is supplied without passing through the Bragg-type semiconductor multilayer reflective film. It is the gist of the present invention to have such an electrode structure, and even in the case where an electrode that penetrates from the rear surface, that is, the substrate side to a part of the reflective layer surface or the clad layer is formed, the multilayer reflective layer is partially The reflective layer may be formed with a region in which a short circuit occurs. FIG.
And FIG. 4 shows such an embodiment.
That is, FIG. 3 shows the DH according to the third embodiment of the present invention.
The sectional structure of the n-type LED is shown. A groove penetrating the Bragg-type semiconductor multilayer reflective film 12 is formed from the n-GaAs substrate 1 side, an n-type electrode 18 is formed at the bottom of this groove, and n-A
A current can be supplied to the l _0.5 In _0.5 P cladding layer 13 from the back surface side. That is, the DH type LED according to the third embodiment of the present invention is the n-GaAs substrate 10.
N-GaAs buffer layer 11 and high refractive index film n-
A semiconductor multilayer reflective film 1 composed of (Al _0.5 Ga _0.5 ) _0.5 In _0.5 P and a low refractive index film n-Al _0.5 In _0.5 P.
2 is formed, and n-Al _0.5 In _0.5 P is further formed on this.
Cladding layer 13, undoped (Al _0.45 Ga _0.55 ) _0.5
In _0.5 P active layer 14, n-Al _0.5 In _0. consisting ₅ P cladding layer 15 DH structure and p-GaAs thereon
It is based on a structure in which the cap layer 16 is sequentially deposited.
As shown in FIG. 3, a part of the n-Al _0.5 In _0.5 P clad layer 13 is partially left from the back surface side by using a predetermined etching solution such as a sulfuric acid-based, hot phosphoric acid-based, and Br-based etching solution. A groove is formed by etching, and an AuGe electrode is formed as the n-type electrode 18 on the etching surface at the bottom of the groove. Next, an AuZn electrode is formed as the p-type electrode 19 on the p-GaAs cap layer 16, and the p-GaAs cap layer 16 is removed by etching except the lower part of the p-type electrode 19. The device thus manufactured is mounted on a lead frame with a conductive adhesive and the substrate side is mounted downward.
The electrode 19 is wire-bonded, and from the n-electrode 18,
Connect directly to the frame with a conductive adhesive.

In the third embodiment of the present invention, a semi-insulating GaAs substrate may be used, and the Bragg type semiconductor multilayer reflective film may be a multilayer film composed of GaAs / AlInP layers. Alternatively, the groove may have a U-shape, a V-shape, or an inverted mesa shape, and the groove may be formed in the central portion instead of forming the groove near the end portion as shown in FIG.

FIG. 4 shows a D according to the fourth embodiment of the present invention.
This is a case where a schematic cross-sectional structure of an H-type LED is provided, and a short-circuit region 45 that brings the Bragg-type semiconductor multilayer reflective film 12 into a short-circuit state is provided. In FIG. 4, an n-GaAs substrate 10
Through the n-GaAs buffer layer 11 (Al
_0.5 Ga _0.5 ) _0.5 In _0.5 P / Al _0.5 In _0.5 P, the semiconductor multilayer reflective film 12, and n-Al _0.5 I.
n _0.5 P cladding layer 13, undoped (Al _0.45 Ga
_0.55 ) _0.5 In _0.5 P active layer 14, n-Al _0.5 In
_A DH structure composed of a _0.5 P clad layer 15 is deposited, and a p-GaAs cap layer 16 is formed on the uppermost layer.
Then, the semiconductor multilayer reflective film 12 is penetrated from the n-Al _0.5 In _0.5 P cladding layer 13 and the n-GaAs substrate 10 is formed.
A short-circuit region 45 is formed by diffusing n-type impurities such as Si and Se to reach a high concentration. An insulating region 44 is formed on the short circuit region 45. n-GaAs substrate 1
On the back surface of 0, an AuGe electrode is formed as the n-type electrode 18. An AuZn electrode is formed as a p-type electrode 19 on the p-GaAs cap layer 16, and the p-GaAs cap layer 16 is removed by etching except the lower part of the p-type electrode 19 so that light can be effectively extracted. Although not shown in FIG. 4, this element is mounted on the lead frame with the substrate side down by a conductive adhesive, and wire bonded to the p electrode 19.

The DH type LED of FIG. 4 is MOCVD, MBE.
Buffer layer 11, on the n-GaAs substrate 1 using
Semiconductor multilayer reflective layer 12, AlInP / AlGaInP
DH structure 13, 14, 15, p-GaAs cap layer 1
6 is deposited by continuous epitaxial growth, the surface of the light emitting region is covered with a metal mask such as Al by photolithography, and multi-stage ion implantation is performed while sequentially changing the acceleration voltage between 1 MeV and 10 MeV.
Ions of Se and Se are selectively ion-implanted to a predetermined depth penetrating the semiconductor multilayer reflection layer and the like, and then heat-treated to form the short-circuit region 45. Further, B (boron) or hydrogen (H) is ion-implanted, and n-Al _0.5 In _0.5 P
Cladding layer 15 and undoped (Al _0.45 G
a _0.55 ) _0.5 In _0.5 P A predetermined portion of the active layer 14 may be selectively used as a high resistance region to form the insulating region 44.
When the damage due to ion implantation becomes a problem, as in the first embodiment of the present invention, a sulfuric acid type, a hot phosphoric acid type, and Br are used.
P-GaAs cap layer 1 using a system etching solution or the like
6, n-Al _0.5 In _0.5 P clad layer 15, ...,
The n-GaAs buffer layer 11 is selectively removed by etching to form a U-shaped or V-shaped groove or the like, and the inside of the groove is 1 ×.
A method of epitaxial growth to backfill with an n ⁺ GaAs or n ⁺ Al _0.5 In _0.5 P layer of about 10 ^{18 to} 5 × 10 ¹⁸ cm ^-3 , selective CVD of refractory metal such as W, Ti, WSi ₂ etc. Alternatively, the short circuit region 45 may be formed by backfilling the groove to a predetermined depth by selective CVD of refractory metal silicide. The upper part of the short-circuit region 45 formed by selective CVD or epitaxial growth may be a so-called air-cap insulating region 44, or SiO ₂ or the like may be formed by CVD, vapor deposition, or sputtering to form the insulating region 44. Or Ga
The insulating region 44 may be formed by anodic oxidation of As. The semiconductor multilayer reflective layer 12 according to the fourth embodiment of the present invention may be a reflective layer made of a GaAs / AlInP layer, or another Bragg type reflective layer.

In the above embodiment, (Al _0.45 G
a _0.55 ) _0.5 In _0.5 P DH type LED has been described, but the present invention is not limited to GaAs type, AlGaAs type, InAl.
Of course, it can be applied to other DH type LEDs such as GaAs type or ZnSe type. In the above description of the embodiments, p and n may be replaced with each other.

[0040]

According to the present invention, even when the semiconductor multi-layer film is provided, the element resistance can be as low as that of the element without the semiconductor multi-layer film. Therefore, the forward voltage is lowered and the heat generation is reduced. , The power consumption is significantly reduced. For example, the forward voltage of an LED having a conventional semiconductor multilayer film was 2.0 V at 20 mA, but it was 1.9 V in the present invention.

Further, according to the present invention, the carriers overflowing from the DH structure provided on the semiconductor multilayer film structure pass through the semiconductor multilayer film and reach the GaAs substrate side,
No more emitting infrared light in the GaAs buffer layer,
Effective in reducing infrared light. Therefore, if such an element is used for an optical fiber for communication, which has been attracting attention in recent years, malfunction can be prevented and its merit is great. At the same time, since there is no fear of carriers overflowing to the GaAs substrate side, it is easy to select the Al composition to the optimum value in order to obtain the emission color of yellow or green, and therefore the design of the LED can be facilitated. Has great value.

Furthermore, since there is no need to worry about the band offset problem of the Bragg type multilayer reflective film, any material,
Since an arbitrary composition can be selected and a multilayer reflective film having a thickness of 20 cycles or more can be freely formed, an extremely highly efficient reflective film can be realized. Therefore, it is easy to increase the brightness and efficiency of the LED.

Further, according to the present invention, since no current flows through the substrate, deterioration or loss due to crystal imperfections such as crystal defects of the substrate can be prevented, and therefore, the LED has a long life and high performance. Efficiency can be improved.

[Brief description of drawings]

FIG. 1 is a DH type LED according to a first embodiment of the present invention.
It is a schematic diagram which shows the cross-sectional structure of.

FIG. 2 is a DH type LED according to a second embodiment of the present invention.
It is a schematic diagram which shows the cross-sectional structure of.

FIG. 3 is a DH type LED according to a third embodiment of the present invention.
It is a schematic diagram which shows the cross-sectional structure of.

FIG. 4 is a DH type LED according to a fourth embodiment of the present invention.
It is a schematic diagram which shows the cross-sectional structure of.

FIG. 5 is a schematic view showing a cross-sectional structure of a DH type LED in the related art.

[Explanation of symbols]

10 n-type GaAs substrate 11 an n-type GaAs buffer layer 12 of n-type semiconductor multilayer reflective film _{13 n- (Al x Ga 1-} x) 0.5 In 0.5 P cladding layer 14 of undoped _{(Al y Ga 1-y)} 0.5 In _0.5 P active layer 15 p- (Al _x Ga _1-x ) _0.5 In _0.5 P clad layer 16 p-GaAs cap layer 17 multilayer reflective film surface 18 n-type electrode 19 p-type electrode 20 semi-insulating GaAs substrate 21 high resistance GaAs Buffer layer 22 Semiconductor multilayer reflective film 23 n-Al _0.5 In _0.5 P clad layer 24 Undoped (Al _0.45 Ga _0.55 ) _0.5 In _0.5 P
Active layer 25 p-Al _0.5 In _0.5 P clad layer 27 Multilayer reflective film surface 30 n-type GaAs substrate 31 n-type GaAs buffer layer 32 n-type semiconductor multi-layer reflective film 33 n-Al _0.5 In _0.5 P clad layer 34 undoped (Al _0.45 Ga _0.55 ) _0.5 In _0.5 P
Active layer 35 p-Al _0.5 In _0.5 P clad layer 36 p-GaAs cap layer 37 n-type electrode 38 p-type electrode 44 insulating region 45 short-circuit region

Front page continuation (72) Inventor Katsumi Kondo 72 Horikawa-cho, Sachi-ku, Kawasaki-shi, Kanagawa Stock company Toshiba Horikawa-cho factory

Claims (10)

[Claims] 1. A semiconductor substrate, a Bragg-type semiconductor multilayer reflective film (hereinafter referred to as a reflective film) provided on an upper surface of the semiconductor substrate, and a light emitting layer having a pn junction provided on the reflective film. A light emitting element having at least a first metal electrode and a second metal electrode for applying a current to the pn junction, wherein a current applied to the pn junction flows without passing through the reflection film. Therefore, a light emitting device having a first metal electrode and a second metal electrode arranged therein. 2. The light emitting layer composed of the pn junction includes at least a first-conductivity-type first semiconductor region and a second-conductivity-type second semiconductor region, and the first semiconductor region is the The second semiconductor region is formed on the reflective film, and the second semiconductor region is formed on the first semiconductor region.
The first metal electrode is formed on an upper portion of the semiconductor region, the first metal electrode is formed on a bottom portion of a groove portion which penetrates the second semiconductor region from an upper side of the second semiconductor region and reaches the first semiconductor region. The light emitting device according to claim 1, wherein the second metal electrode is formed on the second semiconductor region. 3. A first gap between the reflection film and the semiconductor substrate.
The light emitting device according to claim 2, wherein a conductive type buffer layer is formed. 4. The light emitting device according to claim 2, wherein a second conductive type cap layer is formed between the second semiconductor region and the second metal region. 5. The light emitting layer formed of the pn junction is sandwiched between a first conductivity type first cladding layer, a second conductivity type second cladding layer, and the first and second cladding layers. The light emitting device according to claim 1, further comprising a double heterojunction structure including an undoped active layer. 6. The cladding layer is (Al _x Ga _1-x )
_0.5 In _0.5 a P layer, the active layer (Al _y Ga
The light emitting device according to claim 5, which is a _1-y ) _0.5 In _0.5 P layer. 7. The light emitting device according to claim 1, wherein the semiconductor substrate is a semi-insulating GaAs substrate. 8. The light emitting layer formed of the pn junction includes at least a first semiconductor region of a first conductivity type and a second semiconductor region of a second conductivity type, and the first semiconductor region is the reflection layer. The second semiconductor region is formed on the first semiconductor region, the first metal electrode penetrates the reflection film from the back surface of the semiconductor substrate, and the second metal region is formed on the reflection film. The light emitting device according to claim 1, wherein the second metal electrode is formed on a bottom of a groove reaching the first semiconductor region, and the second metal electrode is formed on an upper part of the second semiconductor region. 9. The light emitting layer formed of the pn junction includes at least a first semiconductor region of a first conductivity type and a second semiconductor region of a second conductivity type, and the first semiconductor region is the reflection layer. The second semiconductor region is formed on the first semiconductor region, the first metal electrode is formed on the first film, and the first metal electrode is formed on the first film. To be electrically connected to the first semiconductor region via a region (hereinafter referred to as a short-circuit region) that electrically short-circuits the semiconductor region and the semiconductor substrate.
The light emitting device according to claim 1, wherein the second metal electrode is formed on a back surface of the semiconductor substrate, and the second metal electrode is formed on an upper portion of the second semiconductor region. 10. The light emitting device according to claim 10, wherein an insulating region is provided on the short circuit region.