JP4382912B2 - AlGaInP light emitting diode - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a high-intensity AlGaInP light emitting diode having a current blocking function.
[0002]
[Prior art]
(Al_XGa_1-X)_YIn_1-YP (0.ltoreq.X.ltoreq.1, 0.ltoreq.Y.ltoreq.1) (hereinafter abbreviated as AlGaInP). In particular, the indium composition ratio (= 1-Y) is set to 0.5 (Al._XGa_1-X)_0.5In_0.5P (0.ltoreq.X.ltoreq.1) has an advantage of achieving good lattice matching with a gallium arsenide (GaAs) single crystal (see Appl. Phys. Lett., 57 (27) (1990), pages 2937 to 2939). . For this reason, for example, it is used as a crystal layer for constructing a light emitting element such as a light emitting diode (LED) or a laser diode (LD) that emits a reddish orange color (Appl. Phys. Lett., 64 (21). (1994), pages 2839 to 2841).
[0003]
In a conventional high-luminance AlGaInPLED having a pn junction type double hetero (DH) structure, a window layer (window layer) is usually disposed above the light emitting portion of the DH structure (SPIE, Vol. 3002 (1997), pages 110-118). The window layer needs to be made of a semiconductor material that is difficult to absorb light emitted from the light emitting layer and is transparent to light emission and has a large forbidden band width in order to improve the light emission extraction efficiency. Further, since the window layer is a crystal layer that also plays a role of widely diffusing the element operating current to the group III-V compound semiconductor crystal layer constituting the LED in order to expand the light emitting area, a crystal having a resistance as low as possible. It is customary to consist of layers.
[0004]
In the prior art, there is an example in which the window layer is made of a transparent oxide. For example, in an AlGaInPLED according to the invention of US Pat. No. 5,481,122, a window layer made of an indium-tin oxide (abbreviated as ITO) layer is disposed on a p-type ohmic contact layer. Further, a means for providing a transparent film made of indium oxide, tin oxide, zinc oxide or magnesium oxide is disclosed (see JP-A-11-17220).
[0005]
Since many oxide crystals have a large band gap exceeding 3 eV at room temperature, it is possible to form a window layer that is advantageous for extraction of emitted light to the outside. On the other hand, good ohmic contact is not stably manifested between the oxide crystal and the III-V group compound semiconductor crystal constituting the AlGaInPLED. For this reason, the forward voltage (so-called Vf) of the LED cannot be reduced, and there is a problem in obtaining a uniform Vf.
[0006]
On the other hand, a technology is disclosed in which an ITO layer is provided via a zinc (Zn) or gold (Au) / Zn alloy film provided on the entire surface of the p-type III-V compound semiconductor crystal layer constituting the AlGaInPLED. (See Japanese Patent Application Laid-Open No. 11-4020). Compared to the semiconductor crystal material constituting the AlGaInPLED, such a metal or alloy film is a good conductor having better conductivity. Therefore, there is an advantage that the element operating current distributed from the electrode laid on the ITO window layer can be diffused over a wide range in a plane toward the AlGaInP light emitting portion.
[0007]
In an LED in which light emission is extracted to the outside from the oxide window layer side, light emission from a region below the electrode provided in the window layer is shielded by the electrode and cannot be efficiently extracted to the outside. Therefore, the operating current distributed in the projected area of the electrode provided in the light emission extraction direction is wasted without making a corresponding contribution to the improvement of the external light emission efficiency.
[0008]
However, in the conventional invention described in Japanese Patent Application Laid-Open No. 11-4020, the metal film is uniformly arranged on the entire surface immediately below the oxide window layer regardless of the positional relationship with the electrode. Yes. In other words, the device operating current is distributed substantially uniformly until reaching the region where light emission is shielded by the electrodes. For this reason, there is a problem that efficient high luminance cannot be achieved sufficiently.
[0009]
[Problems to be solved by the invention]
An object of the present invention is to provide a window comprising a transparent oxide layer in order to develop a good ohmic junction with a group III-V compound semiconductor crystal layer constituting an AlGaInPLED. In an AlGaInPLED in which a metal thin film is interposed immediately below a layer, a configuration capable of exhibiting a function of preventing the operating current from flowing to a region immediately below the electrode is presented.
[0010]
[Means for Solving the Problems]
The inventors arrived at the present invention as a result of diligent efforts to solve the above problems. That is, the present invention
[1] In an AlGaInP light-emitting diode having a window layer containing an oxide and an electrode on a III-V compound semiconductor crystal layer via a metal thin film, the projected region of the electrode in the III-V compound semiconductor crystal layer is An AlGaInP light emitting diode characterized by being ion-implanted,
[2] The group III-V compound semiconductor crystal layer is an n-type layer, the ion-implanted element is an acceptor impurity, and is an element different from the metal thin film. AlGaInP light emitting diode,
[3] The group III-V compound semiconductor crystal layer is a p-type layer, the ion-implanted element is a donor impurity, and is an element different from the metal thin film. AlGaInP light emitting diode,
[4] The AlGaInP light-emitting diode according to any one of [1] to [3], wherein hydrogen or oxygen is ion-implanted,
[5] The AlGaInP light-emitting diode according to any one of [1] to [4], wherein the metal thin film is provided in a region other than the projected region of the electrode.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The light-emitting diode of the present invention has a structure having a window layer containing an oxide and an electrode on a group III-V compound semiconductor crystal layer via a metal thin film, and the light-emitting portion is made of (Al_XGa_1-X)_YIn_1-YP (0 ≦ X ≦ 1, 0 ≦ Y ≦ 1), preferably (Al_XGa_1-X)_0.5In_0.5P (0 ≦ X ≦ 1).
[0012]
In the III-V compound semiconductor constituent layer on which the metal thin film is deposited, the region where ion implantation is performed is at least the surface layer portion of the projection region in the vertical direction of the electrode disposed on the oxide window layer. The planar shape of the ion implantation region is preferably substantially similar to the bottom shape of the electrode. In addition, it is desirable that the center of the planar shape of the electrode and the planar shape of the ion implantation region substantially match. For example, if the bottom surface shape of the electrode that joins the window layer is a square, the ion implantation regions also have a square shape in which the centers of the shapes are substantially coincided with each other and have a similar relationship.
[0013]
A III-V compound semiconductor constituent layer having a metal thin film and having an ion implantation region can be obtained, for example, by the following means.
(1) Means for implanting impurity ions in advance into the projected region of the electrode on the surface of the III-V compound semiconductor constituent layer using a known patterning technique, and then crowning the surface of the constituent layer with a metal thin film.
(2) After depositing a metal thin film on the surface of the III-V group compound semiconductor constituent layer, without removing the metal thin film, ion implantation is selectively performed in a region corresponding to the projected region of the electrode. Means through through ion implantation techniques.
[0014]
The metal film to be deposited on the III-V group compound semiconductor constituting layer constituting the AlGaInPLED is preferably made of a metal having ohmic contact with the III-V group compound semiconductor crystal. For the n-type III-V compound semiconductor crystal layer, for example, nickel (Ni), nickel oxide (NiO), indium (element symbol: In), Au-germanium (Ge) alloy, Au-tin (Sn) alloy A metal thin film can be composed of an In—Sn alloy. The metal thin film on the surface of the p-type III-V compound semiconductor crystal layer can be preferably composed of Ni, NiO, Au—Zn alloy, Au—beryllium (Be) alloy, In—Zn alloy, or the like.
[0015]
Conversely, ion species composed of elements other than those constituting the metal thin film are implanted into the ion implantation region. As described above, since the ion implantation region is provided in order to inhibit the flow of the drive current directly below the electrode, the region needs to be non-ohmic with respect to the III-V group compound semiconductor crystal layer. It depends. Therefore, ions other than In, Sn, and Ge are implanted into the n-type III-V compound semiconductor constituent layer. In particular, for n-type III-V compound semiconductor constituent layers, group II elements such as Zn, magnesium (Mg) or Be, or carbon belonging to group IV (element symbol: C) are suitable implanted ion species. is there. Since such an element acts as an acceptor impurity for the III-V compound semiconductor, by implanting these impurity ions into the n-type III-V compound semiconductor constituent layer, the pn is implanted into the ion implantation region. There exists an advantage which can form a junction part. By forming the ion implantation region including the pn junction, the flow of the element driving current to the region immediately below the electrode is more reliably blocked. In order to make the implanted atom act as an electrically active acceptor, activation annealing is performed after the implantation. Annealing of implanted atoms that are relatively difficult to diffuse in III-V group compound semiconductors such as C, Be, and Mg is generally performed at 700 to 850 ° C. It is recommended that the readily diffusible Zn activation annealing be performed at a lower temperature of about 600 ° C. to about 700 ° C.
[0016]
In the p-type group III-V compound semiconductor constituent layer, if a donor impurity ion is implanted into the group III-V compound semiconductor, an ion implantation region including a pn junction can be formed. Donor ion species suitable for implantation include Group IV elements such as silicon (Si) and Sn, or ions of Group VI elements such as sulfur (element symbol: S), selenium (Se) and tellurium (Te). . The ion species to be implanted is not limited to one type, and a plurality of donor impurities may be implanted simultaneously. After the n-type impurity is ion-implanted into the p-type III-V compound semiconductor constituent layer, annealing is performed to electrically activate the implanted impurity. For n-type impurities having a small diffusion constant in III-V group compound semiconductors such as Si, the annealing temperature is generally set to 800 ° C. to 850 ° C. For n-type impurities that are more likely to diffuse than silicon such as Se and Te, it is recommended that the annealing temperature be lower than about 700 ° C. to about 750 ° C.
[0017]
Further, the drive current to the region directly under the electrode can be obtained by means of implanting ions of an element that forms a deep impurity level in a III-V compound semiconductor and forming a high-resistance ion-implanted region. It is effective in obstructing the inflow of water. Examples of ionic species suitable for forming the high resistance region include oxygen ions. For example, an n-type aluminum arsenide / gallium crystal (Al_XGa_1-XEven if Zn ions are implanted simultaneously with oxygen ions into a III-V group compound semiconductor constituent layer composed of As: 0 ≦ X ≦ 1), an ion implantation region including a high resistance or a pn junction can be configured.
[0018]
In addition, a high-resistance ion-implanted region can be formed by implanting hydrogen ions (protons) that electrically inactivate donor or acceptor impurities. Since hydrogen ions are smaller in mass number and smaller in atomic radius than the metal ions as described above, they can be implanted deeper into the III-V compound semiconductor crystal layer under the same acceleration voltage. That is, hydrogen ions are an implanted ion species suitable for forming a high resistance layer until reaching a deep layer in the III-V compound semiconductor crystal layer. After the implantation of hydrogen ions, the situation is different from the case of the n-type or p-type impurity described above, and activation annealing is not performed or is performed at a low temperature of about 400 ° C. or lower. This is because, under a high temperature environment, hydrogen deviates from the III-V group compound semiconductor crystal layer, so that high resistance cannot be achieved. Although the resistance can be increased even if argon (Ar) or the like is implanted, the technique of ion implantation of atoms having a relatively large atomic radius causes a large implantation damage, and the crystallinity of the III-V compound semiconductor constituent layer Is not suitable because of worsening.
[0019]
When a high resistance region is formed by implanting ions as described above, if the plane area of the implantation region is set to be extremely large, the area where the LED drive current can be diffused decreases. For this reason, high brightness of the AlGaInPLED cannot be sufficiently achieved. Convenient for hindering the flow of drive current to the region directly under the electrode, and the plane area of the ion implantation region that does not hinder high brightness is about 0.7 times the bottom area of the electrode To about 1.2 times.
[0020]
The amount of ions implanted into the ion implantation region is set to an amount that can substantially compensate electrically the carriers of the III-V group compound semiconductor crystal layer to be implanted. For example, the electron concentration is about 1 × 10¹⁸cm^-3In the n-type III-V compound semiconductor crystal layer, about 1 × 10¹⁸cm^-3Alternatively, for example, Mg ions are implanted so as to obtain a hole concentration exceeding that. The hole concentration can be increased or decreased by adjusting the amount of Mg ions implanted, the so-called dose amount. Further, the depth from the surface of the III-V compound semiconductor constituent layer through which the implanted ion species permeates can be controlled by adjusting the acceleration voltage of ions at the time of implantation. According to so-called multistage implantation means in which the acceleration voltage is varied, an ion implantation layer having a substantially uniform carrier concentration in the depth direction can be formed. Increasing the depth of ion penetration increases the thickness of the high resistance region, for example. In the case of the present invention, it is sufficient that the thickness of the high resistance region is about 50 nanometers (nm) or more that can prevent carrier penetration due to the tunnel effect.
[0021]
The metal thin film that provides ohmic contact between the window layer containing oxide and the III-V group compound semiconductor constituent layer may be deposited on the entire surface of the constituent layer, but other than the projected region below the electrode. If it is specifically arranged on the outer periphery of, the effect of blocking the current is further exhibited. That is, it is selectively laid in a region around the ion implantation region in the projection region directly under the electrode. According to this arrangement method of the metal thin film, it is further prevented that the operating current flows into the ion implantation region where the high resistance or pn junction is formed through the metal thin film which is a good conductor, and priority is given to the surrounding area. Operating current can be distributed.
[0022]
In order to selectively dispose the metal thin film around the outer periphery of the area except for the projected area of the electrode directly under the electrode, (1) deposit the metal thin film on the surface of the III-V compound semiconductor constituent layer; 2) Next, the metal thin film in a region corresponding to the projected region of the electrode is selectively removed by using a photolithography technique. (3) Next, the opened and exposed III-V compound semiconductor crystal is exposed. It can be configured by implanting ions into the surface of the layer. (1) In advance, ion implantation is performed only in the projected region of the electrode. (2) Next, a metal thin film is deposited on the entire surface of the III-V compound semiconductor layer. (3) Next, ion implantation is performed. Only in the region, the metal thin film can be selectively removed. The planar shape of the region from which the metal thin film is removed is substantially similar to that of the ion implantation region. Both regions may be completely matched, and both regions may overlap each other with a width of several μm at the outer peripheral edge, or may be arranged with a gap.
[0023]
The window layer provided on the metal thin film or the ion implantation region is, for example, zinc oxide (ZnO), tin oxide (chemical formula: SnO₂), Indium oxide (chemical formula: In₂O_Three), Titanium oxide (Ti0, TiO₂), Gallium oxide (chemical formula: Ga₂O_Three), Nickel oxide (chemical formula: NiO), manganese oxide (chemical formula: MnO), copper oxide (chemical formula: CuO), and the like. Moreover, it can comprise from complex oxides, such as ITO. In particular, an oxide having a forbidden band width of about 2 electron volts (eV) or more that can sufficiently transmit the red-orange light emitted from the AlGaInP light-emitting layer can be preferably used as a constituent material of the window layer. A conductive oxide material having a large forbidden band width and a low resistivity of about 1 milliohm · centimeter (mΩ · cm) or less in specific resistance can reduce the operating current of an LED in a planar manner. It can be advantageously used as a window layer that also serves as a current diffusion layer that diffuses into the window.
[0024]
  The window layer can also be configured by stacking a plurality of oxide crystal layers. For example, there is an example of a multilayer structure window layer in which the lower layer is an ITO layer and the upper layer is a ZnO layer to which gallium (Ga) is added. By laminating crystal layers made of oxides having different refractive indexes so that the refractive index gradually becomes smaller upward, a more convenient window layer can be configured to transmit light emitted from the light emitting layer.
[0025]
【Example】
Example 1
  Example 1 is shown as a reference example.
  In the present embodiment, the present invention will be described in detail by taking an AlGaInPLED 10 provided with a window layer containing ITO on the epitaxial multilayer structure 20 as an example. FIG. 1 is a schematic cross-sectional view of an LED 10 according to this embodiment.
[0026]
The laminated structure 20 includes a Zn-doped p-type GaAs single crystal substrate 101, an Mg-doped p-type GaAs buffer layer 102, an Mg-doped p-type (Al_0.7Ga_0.3)_0.5In_0.5P lower cladding layer 103, undoped (Al_0.2Ga_0.8)_0.5In_0.5P light-emitting layer 104 and Si-doped n-type (Al_0.7Ga_0.3)_0.5In_0.5The P upper clad layer 105 is used. Each layer of the epitaxial constituent layers 102 to 105 is formed of trimethylgallium ((CH_Three)_ThreeGa) / trimethylaluminum ((CH_Three)_ThreeAl) / trimethylindium ((CH_Three)_ThreeIn) / phosphine (PH_Three) Growing at 730 ° C. by the reduced pressure MO-VPE method. Diethyl zinc ((C₂H_Five)₂Zn), magnesium doping source is bis-cyclopentadienyl Mg ((C_FiveH_Five)₂Mg) was used. The silicon doping source is disilane (Si₂H₆) In a concentration of about 10 ppm by volume.
[0027]
As the substrate 101, a GaAs single crystal inclined by 4 ° in the <011> direction was used. The carrier concentration of the substrate 101 is about 2 × 10.¹⁹cm^-3The layer thickness was about 300 μm. The thickness (d) of the GaAs buffer layer 102 is 1.5 μm, and the carrier concentration (p) is about 2 × 10.¹⁸cm^-3It was. The lower cladding layer 103 has d = 3.5 μm and p = 3 × 10¹⁸cm^-3It was. The light emitting layer 104 has d = 0.2 μm and carrier concentration (n) = 1 × 10.¹⁷cm^-3It was. The upper cladding layer 105 has d = 1 μm, and n = 7 × 10¹⁷cm^-3It was.
[0028]
A region corresponding to the projected region 111 of the electrode 109 on the window layer 107 described later was patterned on the upper clad layer 105 by using a known photolithography technique. The patterned region 111 is a circle having a diameter of about 130 μm, which is similar to the shape of the bottom surface of the electrode 109. Thereafter, Mg ions are applied to the n-type upper clad layer 105 whose surface is exposed in a specific region corresponding to the projected region 111 of the electrode 109, with the photoresist material used for patterning the metal thin film 106 crowned. The acceleration voltage was injected at 200 kilovolts (KV). The dose amount is 8.0 × 10¹²cm^-2Set to. After the ion implantation, the photoresist material covering the surface was peeled off, annealed in an argon (Ar) stream at 720 ° C. for 30 minutes, and the implanted Mg ions were electrically activated as an acceptor. . Thus, a pn junction was formed inside the projection region (= ion implantation region) 111.
[0029]
After activation annealing, n-type (Al_0.7Ga_0.3)_0.5In_0.5A thin film 106 made of Ni was deposited on the entire surface of the P upper cladding layer 105 by a general vacuum deposition method. The film thickness was about 10 nm. It was visually recognized that the Ni film 106 immediately after deposition was gray.
[0030]
On the metal thin film 106, a window layer 107 made of an ITO film exhibiting n-type conduction was bonded. The transparent conductive window layer 107 has a specific resistance of about 9 × 10 6 by high frequency magnetron sputtering.^-FourIt was composed of ITO with Ω · cm. The thickness of the ITO layer deposited at about 300 ° C. was about 0.25 μm.
[0031]
On the surface of the window layer 107, silicon nitride (Si having a refractive index smaller than that of ITO)_ThreeN_Four) (Refractive index of about 1.9) was deposited as the surface protection film 108 of the oxide window layer 107. The silicon nitride protective film 108 is monosilane (SiH_Four) And ammonia (NH_Three) As a raw material by a known plasma CVD method. The layer thickness was about 0.15 μm.
[0032]
An Au—Zn alloy (Au 98 wt% —Zn 2 wt%) film was deposited on the back surface of the p-type GaAs substrate 101 by a general vacuum deposition method. The film thickness was about 0.5 μm. Thereafter, an alloying process was performed at 430 ° C. for 5 minutes in an Ar air stream to form a p-type ohmic electrode 110.
[0033]
After the alloy process, it was visually confirmed that the Ni film 106 was decolorized and became almost transparent. This was mainly determined because the Ni film 106 was oxidized and converted to nickel oxide such as NiO by the oxygen contained in the ITO film 107 that forms the upper layer of the Ni film 106.
[0034]
Next, the silicon nitride protective film 108 in the region where the n-type electrode 109 is to be formed was partially removed using a known photolithography technique. In the region where the silicon nitride protective film 108 is removed and the surface of the ITO layer forming the window layer 107 is exposed, the lower bottom portion 109a in contact with the ITO layer is made of titanium (Ti), and the upper layer portion 109b is made of aluminum (Al). An n-type electrode 109 having a multilayer structure was formed. The n-type electrode 109 was a circular electrode having a diameter of about 120 μm.
[0035]
When a current of 20 milliamperes (mA) was passed in the forward direction between the n-type electrode 109 and the p-type ohmic electrode 110, red-orange light emission was obtained almost uniformly from the substantially entire surface of the window layer 107. The emission wavelength measured by the spectroscope was about 621 nm. The half width of the emission spectrum was about 19 nm, and light emission excellent in monochromaticity was obtained. In addition, the ohmic junction between the upper cladding layer 105 and the window layer 107 is improved by the provision of the metal thin film 106. For this reason, the forward voltage (@ 20 mA) was reduced to 1.94 volts (V) on average. The emission intensity reached approximately 54 millicandelas (mcd).
[0036]
(Example 2)
An example in which the AlGaInPLED 30 shown in FIG. 2 is formed after implanting Zn ions into a specific region on the surface of the n-type upper cladding layer 105 using the same epitaxial multilayer structure 40 as described in the first embodiment. The present invention will now be described. The same components as those in the laminated structure 20 of the first embodiment are denoted by the same reference numerals (see FIG. 1), and the description thereof is omitted.
[0037]
In this embodiment, first, n-type (Al_0.7Ga_0.3)_0.5In_0.5A thin film 106 made of Ni was deposited on the entire surface of the P upper cladding layer 105 by a general vacuum deposition method. The film thickness was about 10 nm. It was visually recognized that the Ni film 106 immediately after deposition was gray. Next, the metal thin film 106 in the region corresponding to the projected region 111 of the electrode 109 on the window layer 107 was selectively removed using a known photolithography technique. The region 111 from which the Ni film was removed was circular with a diameter of about 110 μm, which was similar to the bottom shape of the electrode 109.
[0038]
Thereafter, Zn ions are applied to the n-type upper clad layer 105 whose surface is exposed in a specific region corresponding to the projected region 111 of the electrode 109, with the photoresist material used for patterning the metal thin film 106 crowned. The acceleration voltage was injected at 150 KV. The dose amount is 4.0 × 10¹²cm^-2Set to. After the ion implantation, the photoresist material covering the surface was peeled off, and annealed in an Ar stream at 650 ° C. for 20 minutes to electrically activate the implanted Zn ions as an acceptor.
[0039]
After the activation annealing, an Al-doped n-type zinc oxide layer (refractive index = 2.0) 107a was laminated on the metal thin film 106 by using a general magnetron sputtering method. The sputtering pressure was about 0.8 Torr, and the deposition temperature was about 300 ° C. The high-frequency power was about 100 W, the deposition time was 25 minutes, and a zinc oxide layer 107a having a layer thickness of about 0.25 μm was obtained. An ITO layer 107b was deposited on the zinc oxide layer 107a mainly for the purpose of protecting the chemically weakly resistant ZnO layer. The thickness of the ITO layer 107b was about 0.3 μm. The specific resistance of the ITO layer 107b is about 2 × 10^-3It was set to Ω · cm. The transparent conductive window layer 107 was configured with the ZnO layer as the first window layer constituting layer 107a and the ITO layer as the second window layer constituting layer 107b.
[0040]
On the surface of the window layer 107, silicon dioxide (SiO 2) having a refractive index smaller than that of ITO.₂) (The refractive index of about 1.6) was deposited as the surface protective film 108 of the oxide window layer 107. The silicon nitride protective film 108 is monosilane (SiH_Four) And oxygen (O₂) As a raw material by a known plasma CVD method. The layer thickness was about 0.10 μm.
[0041]
An Au—Zn alloy (Au 98 wt% —Zn 2 wt%) film was deposited on the back surface of the p-type GaAs substrate 101 by a general vacuum deposition method. The film thickness was about 0.5 μm. Thereafter, an alloying process was performed at 430 ° C. for 5 minutes in an Ar air stream to form a p-type ohmic electrode 110.
[0042]
After the alloy treatment, it was visually recognized that the Ni film 106 was decolored and became substantially transparent. This was mainly determined because the Ni film 106 was oxidized and converted to nickel oxide such as NiO by the oxygen contained in the ITO film 107 that forms the upper layer of the Ni film 106.
[0043]
Next, the silicon dioxide protective film 108 in the region where the n-type electrode 109 is to be formed was partially removed using a known photolithography technique. In the region where the silicon dioxide protective film 108 is removed and the surface of the ITO layer forming the window layer 107 is exposed, an n-type electrode having a multilayer structure in which the lower bottom portion 109a in contact with the ITO layer is Ti and the upper layer portion 109b is Au. 109 was formed. The n-type electrode 109 was a circular electrode having a diameter of about 130 μm.
[0044]
When a current of 20 mA was passed in the forward direction between the n-type electrode 109 and the p-type ohmic electrode 110, red-orange light emission was obtained almost uniformly from the substantially entire surface of the window layer 107. The emission wavelength measured by the spectroscope was about 621 nm. The half width of the emission spectrum was about 19 nm, and light emission excellent in monochromaticity was obtained. In addition, the ohmic junction between the upper cladding layer 105 and the window layer 107 is improved by the provision of the metal thin film 106. For this reason, the forward voltage (@ 20 mA) was reduced to 1.94 V on average. The emission intensity reached about 54 mcd.
[0045]
(Example 3)
An example is shown in which an AlGaInPLED similar to that shown in FIG. 2 is formed after hydrogen ions are implanted into a specific region on the surface of the n-type upper cladding layer 105 constituting the epitaxial multilayer structure 30 described in the second embodiment. The present invention will be described.
[0046]
An Au—Ge alloy film (Au 97 wt% -Ge 3 wt%) having a film thickness of about 8 nm and an Au film having a film thickness of about 2 μm are formed on the entire surface of the n-type upper clad layer 105 described in Example 2. Was continuously applied. Next, using the known photolithography technique, the above-described multilayer metal film was selectively removed only under the region where the n-type electrode 109 was laid. Corresponding to the fact that the n-type electrode 109 is a circular electrode having a planar shape with a diameter of about 120 μm, the diameter of the region from which the metal film has been removed is a circular shape with a diameter of 100 μm. The center of the circular n-type electrode 109 and the center of the region from which the metal film was removed were substantially matched.
[0047]
Next, hydrogen ions (H) are formed on the surface of the n-type upper clad layer 105 exposed in the opened region after the metal film is removed.⁺) Was injected. The acceleration voltage is 40 KV and the dose is about 5 × 10¹²cm^-2Set to. Hydrogen ions were implanted at room temperature, and activation annealing after implantation was not performed in order to avoid deviation of implanted protons. After the implantation, substantially the entire upper Au film constituting the Au · Ge / Au multilayer metal film laid on the outer periphery other than the implantation region 111 in order to prevent intrusion of hydrogen ions is removed, and the lower Au · Ge alloy is removed. Only the film was left as the metal thin film 106 according to the present invention.
[0048]
On the metal thin film 106, an Al-doped n-type zinc oxide layer (refractive index = 2.0) 107a was laminated using a general magnetron sputtering method. The Al-doped n-type ZnO layer was deposited by a general magnetron sputtering method. The sputtering pressure was about 1.0 Torr, and the deposition temperature was about 280 ° C. The high frequency power was about 100 W, the deposition time was 10 minutes, and an ITO layer 107b having a layer thickness of about 0.10 μm was obtained. An ITO layer 107b was deposited on the zinc oxide layer 107a. The thickness of the ITO layer 107b was about 0.3 μm. The specific resistance of the ITO layer 107b is about 7 × 10.^-3It was set to Ω · cm. The transparent conductive window layer 107 was configured with the ZnO layer as the first window layer constituting layer 107a and the ITO layer as the second window layer constituting layer 107b.
[0049]
A protective film 108 made of silicon nitride was crowned on the second window layer constituting layer 107b made of ITO. The protective layer 108 in the region where the n-type electrode 109 is to be formed is selectively removed by a general plasma etching method to expose the surface of the zinc oxide layer 107a, and then the region has a diameter of about 120 μm. An Au circular electrode 109 is provided. Accordingly, the metal thin film 106 is not left in the projection region 111 of the electrode 109, and the metal thin film 106 is disposed only in the peripheral region of the n-type electrode 109.
[0050]
A gold / zinc alloy (Au 98 wt% -Zn 2 wt% alloy) was vacuum deposited on the entire back surface of the GaAs substrate 101, and then alloyed at 420 ° C. for 2 minutes to form a p-type ohmic electrode 110. Thereafter, the same LED as that in FIG. 1 was obtained by cutting into individual chips each having a substantially square shape with a side of about 350 μm. When the metal thin film 106 was made of an Au—Ge alloy, unlike the case of the Ni film of Example 1, particularly noticeable decolorization was not visually recognized after the p-type electrode 110 was alloyed.
[0051]
When a current of 20 mA was passed in the forward direction between the n-type electrode 109 and the p-type ohmic electrode 110, substantially uniform red-orange light emission was obtained from substantially the entire surface of the window layer 107 on which the metal thin film 106 was laid. . The emission wavelength measured by the spectroscope was about 620 nm. The half width of the emission spectrum was about 18 nm, and light emission excellent in monochromaticity was obtained. The forward voltage (@ 20 mA) was as low as 1.95 ± 0.03 V and was uniform. In addition, since the projection region 111 of the electrode 109 is made into a high resistance region by implanting hydrogen ions, the element operating current is preferentially given to the region where the metal thin film 106 is embedded rather than the region immediately below the n-type electrode 109. Since it could be supplied, the emission intensity reached about 50 mcd.
[0052]
【The invention's effect】
According to the first to fourth aspects of the present invention, in an AlGaInPLED having a window layer including a transparent conductive oxide layer, a group III-V compound semiconductor crystal layer and a current constituting the LED are provided. A metal thin film that exhibits good ohmic contact is placed in the middle of the transparent conductive oxide window layer that also plays a role of diffusion, and ion implantation is performed on the region directly below the electrode that is shielded and difficult to extract light emission to the outside. Since the region is a pn junction region or a high resistance region, the LED drive current supplied from the electrode on the window layer can be preferentially and efficiently distributed to a region where it is easy to extract the power to the outside. AlGaInPLED can be provided.
[0053]
According to the invention described in claim 5 of the present invention, the highly conductive metal thin film is disposed only in the outer peripheral region of the region directly under the electrode, while in the region directly under the electrode, Since this region is made a region that performs a current blocking function by performing ion implantation, the operating current of the LED can be more efficiently diffused to the outer periphery of the projected region of the electrode, so that a high-brightness AlGaInP light emitting diode is provided. Can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view of an LED described in Example 1. FIG.
2 is a schematic cross-sectional view of an LED described in Example 2. FIG.
[Explanation of symbols]
10 AlGaInP LED
20 Laminated structure
30 AlGaInP LED
40 Laminated structure
101 GaAs single crystal substrate
102 GaAs buffer layer
103 Lower cladding layer
104 Light emitting layer
105 Upper cladding layer
106 Metal thin film
107 Window layer
107a First window layer constituent layer
107b Second window layer constituent layer
108 Protective film
109 n-type electrode
109a bottom of n-type electrode
109b n-type electrode upper layer
110 p-type ohmic electrode
111 Projection region of electrode (ion implantation region)

Claims (11)

In an AlGaInP light-emitting diode having a window layer containing an oxide and an electrode on the window layer via a metal thin film on the group III-V compound semiconductor crystal layer, the metal thin film is in contact with the surface of the group III compound semiconductor crystal layer. The electrode layer is provided in a region other than the projected region of the electrode, and the window layer has a two-layer structure made of different oxides. At least the surface layer portion of the III-V compound semiconductor crystal layer in the projected region of the electrode has ions. An AlGaInP light emitting diode characterized in that an implanted region is provided.   2. The AlGaInP light-emitting diode according to claim 1, wherein the III-V compound semiconductor crystal layer is an n-type layer, and the ion-implanted element is an acceptor impurity and is an element different from the metal thin film. .   2. The AlGaInP light-emitting diode according to claim 1, wherein the III-V compound semiconductor crystal layer is a p-type layer, the ion-implanted element is a donor impurity, and is an element different from the metal thin film. .   The AlGaInP light emitting diode according to any one of claims 1 to 3, wherein hydrogen or oxygen is ion-implanted. A group III-V compound semiconductor crystal layer having an ion-implanted region is formed of n-type aluminum phosphide / gallium / indium (composition (Al _x Ga _{1 -x} ) _0.5 In _0.5 P: 0 <X ≦ 1). 5. The AlGaInP light emitting diode according to claim 1, wherein the AlGaInP light emitting diode is an upper clad layer.   6. The AlGaInP light-emitting diode according to claim 1, wherein a planar area of a region into which ions are implanted is 0.7 to 1.2 times the bottom area of the electrode.   The AlGaInP light emitting diode according to any one of claims 1 to 6, wherein the two-layer structure is formed by stacking oxide layers having different refractive indexes.   The AlGaInP light emitting diode according to claim 7, wherein the upper layer of the two-layer structure has a refractive index smaller than that of the lower layer.   9. The two-layer structure is configured such that a layer made of indium tin oxide composite oxide (abbreviation: ITO) is an upper layer and a layer made of zinc oxide (ZnO) is a lower layer. AlGaInP light emitting diode.   10. The zinc oxide (ZnO) layer constituting the lower layer of the two-layer structure is composed of n-type zinc oxide to which gallium (element symbol: Ga) or aluminum (element symbol: Al) is added. 2. An AlGaInP light emitting diode according to 1.   10. The AlGaInP light emitting diode according to claim 9, further comprising an insulating film containing silicon (element symbol: Si) having a refractive index smaller than that of the upper layer on the upper layer of the two-layer structure. .

Images