JP2004247411A - Semiconductor light emitting device and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor light emitting device that is excellent in luminous efficiency and reliability at high productivity. <P>SOLUTION: In the semiconductor light emitting device in which a semiconductor growing layer is formed on a substrate, the side face of the substrate is formed in a roughened surface and the side face of the semiconductor growing layer is formed in a flat mirror-finished surface. Since the side face of the semiconductor light emitting device has two areas of a flat mirror-finished surface area and a roughened surface area at right places, the luminous efficiency and reliability of the light emitting device can be improved by controlling both the emission of internal light and the scattering and reflection of return light. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a semiconductor light emitting device such as a light emitting diode device and a semiconductor laser device, and more particularly, to a semiconductor light emitting device having excellent luminous efficiency and reliability and a manufacturing method.
[0002]
[Prior art]
In recent years, as a light emitting material capable of covering a wide range from ultraviolet to green and beyond, crystal growth and device technology of a group III nitride-based semiconductor, which is a wide gap semiconductor, are rapidly developing. Among them, a blue semiconductor laser device having an oscillation wavelength of around 400 nm is expected to be put to practical use, including application to a next-generation high-density light source for digital optical recording._aAl_bGa_1-abVarious device structures have been proposed, such as a multiple quantum well active layer using N.
[0003]
On the other hand, an oxide semiconductor has been attracting attention as a novel light emitting material in order to complement device characteristics that are difficult to achieve with conventional compound semiconductor materials, and has been actively studied in recent years.
Above all, zinc oxide (ZnO) is a direct transition semiconductor having a band gap energy of about 3.4 eV, an exciton binding energy as extremely high as 60 meV, a low-cost raw material, and a harmless environment and human body. However, there is a possibility that a light emitting device having high efficiency, low power consumption, and excellent environmental performance can be realized.
[0004]
Hereinafter, when the term "ZnO-based" semiconductor is used in this specification, it includes ZnO and mixed crystals represented by MgZnO, CdZnO, or the like using the same as a host. Further, in the present specification, when a mixed crystal is indicated without specifying the composition, for example, “MgZnO” is simply described only by an element symbol, and when the composition is specified, for example, “MgZnO” is used._0.1Zn_0.9O ".
[0005]
When a semiconductor laser element is used as a light source for digital optical recording, the "three-beam method" is used to detect the spot position in order to accurately trace the minute pit row recorded on the optical disk surface. The so-called method has been widely adopted.
In the three-beam method, a laser beam emitted from a semiconductor laser element is divided into three beams by a beam splitter, a reflected light intensity difference between two sub-beams is detected, and a fine adjustment drive signal of an optical system device is fed back by a servo mechanism. I do. However, in this method, part of the side beam reflected by the optical disk passes through the half mirror of the beam splitter and returns to the side of the semiconductor laser element as the light source. This return light is focused on the end face of the semiconductor laser element, reflected again on the optical disk side and interferes with a regular beam, causing undulation, and the tracking servo becomes unstable.
[0006]
In order to solve this problem, various devices have been devised for the III-V group semiconductor laser device which has been used as the light source for the optical disk and the optical pickup in which the device is sealed.
[0007]
For example, Japanese Patent Application Laid-Open No. 63-261775 (Patent Document 1) discloses that a dielectric film is formed on the entire end face of a resonator including a growth layer, a resist film is partially formed thereon, and then a resist film is formed. A technique has been disclosed in which the thickness of the dielectric film in the portion where no is formed is reduced to reduce the reflectance of return light.
[0008]
Japanese Patent Application Laid-Open No. 6-302004 (Patent Document 2) discloses that a portion of a light-emitting end face of a semiconductor laser element which receives return light has₂O₃, SiO₂, TiO₂A technique has been disclosed in which a rough dielectric thin film is formed so that the reflectance adjusting layer also has a function of avoiding return light.
[0009]
Since a light emitting element using spontaneous emission light such as a light emitting diode element does not need to have a waveguide mechanism, light from the light emitting layer is emitted in all directions.
[0010]
Of these, light emitted in the lateral direction or above the light emitting layer is easily taken out of the device, and therefore, the side surface of the light emitting diode device is preferably excellent in flatness so as not to cause irregular reflection. On the other hand, light emitted below the light emitting layer is not directly extracted to the outside. Therefore, in order to efficiently reflect the light emitted below the light-emitting layer and take it out of the element, the mounting surface of the lead frame on which the light-emitting diode element is mounted has a cup shape coated with a metal with high light reflectance. Has become. Light emitted obliquely downward from the light emitting layer is reflected at the bottom surface and emitted to the outside of the device from the side surface, and further reflected at the cup side surface and emitted upward. As a mounting example as described above, a light emitting device using a gallium nitride-based compound semiconductor is disclosed in Japanese Patent No. 3065258 (Patent Document 3).
[0011]
[Patent Document 1]
JP-A-63-261775
[0012]
[Patent Document 2]
JP-A-6-302004
[0013]
[Patent Document 3]
Japanese Patent No. 3065258
[0014]
[Problems to be solved by the invention]
The above-described technology for avoiding return light in a semiconductor laser device has poor mass productivity and low accuracy in controlling the thickness and surface roughness of the dielectric film. There is a problem that it becomes difficult.
[0015]
Further, in the example of light extraction in the light-emitting diode element, light emitted obliquely downward from the light-emitting layer is likely to cause total reflection if the bottom surface or lower surface of the substrate is a mirror surface with excellent flatness, and is extracted to the outside. Multiple reflections occur in the element before the light is reflected. In this process, there is a problem that light emission is re-absorbed by the semiconductor and luminous efficiency is reduced.
[0016]
As described above, any of the conventional techniques is poor in controllability of the end face function in the semiconductor light emitting device, and even when applied to a blue semiconductor light emitting device using an oxide semiconductor or the like, which requires more advanced functions and processing accuracy, It was difficult to solve the problem.
Thus, an object of the present invention is to provide a semiconductor light emitting device having excellent luminous efficiency and reliability in view of the above problems.
[0017]
[Means for Solving the Problems]
The present inventor controlled both the extraction of internal light and the scattered reflection of return light by providing two regions, a flat mirror surface and a rough surface, at appropriate positions on the end face of the semiconductor light emitting element, and was excellent in luminous efficiency and reliability. The present inventors have found that a semiconductor light emitting device can be realized, and have reached the present invention.
[0018]
That is, the present invention is characterized in that, in a semiconductor light emitting device in which a semiconductor growth layer is formed on a substrate, the side surface of the substrate is rough, and the side surface of the semiconductor growth layer is a flat mirror surface. Provided is a semiconductor light emitting device.
In the region where the side surface is a mirror surface, light from the inside of the light emitting element is efficiently extracted out of the element without irregular reflection, and on the other hand, by adjusting the reflectance, it can function as a reflecting mirror for amplifying the stimulated emission light by resonance. . Further, in the region where the side surface is rough, light incident from the inside of the device at a total reflection angle or more can be diffused and efficiently extracted to the outside of the device. Can be reduced.
Thus, both light extraction and scattered reflection of the light emitting element are controlled, and a light emitting element excellent in luminous efficiency and reliability can be realized.
[0019]
In a first aspect, the present invention provides at least a first conductive type ZnO-based semiconductor cladding layer, a ZnO-based semiconductor light emitting layer, a second conductive type ZnO-based semiconductor clad layer, and a second conductive type ZnO-based A semiconductor light emitting device on which a semiconductor growth layer including a base semiconductor contact layer is formed, wherein the semiconductor growth layer portion has a mirror-like surface on the device side surface, and the substrate portion has a rough surface on the device side surface. The present invention provides a semiconductor light emitting device characterized by the following. In particular, this semiconductor light emitting device can be applied to a light emitting diode device.
[0020]
In the present specification, the “first conductivity type” and the “second conductivity type” are different from each other and mean n-type or p-type. For example, if the first conductivity type is n-type, the second conductivity type is p-type.
[0021]
In a light-emitting diode element, light emitted from the light-emitting layer is hardly totally reflected on the side surface of the semiconductor growth layer portion and is easily taken out. Therefore, light is returned into the element by irregular reflection by making the side surface a mirror surface. It is effective to prevent. On the other hand, light incident on the side surface of the substrate portion has low light extraction efficiency. Therefore, it is effective to make the side surface rough so that light can be easily extracted out of the element by irregular reflection.
[0022]
In a second aspect, the present invention provides a method for manufacturing a semiconductor device, comprising: forming at least a first conductivity type ZnO-based semiconductor clad layer, a ZnO-based semiconductor active layer, a second conductivity type ZnO-based semiconductor clad layer, a second conductivity type on a substrate; A ZnO-based semiconductor contact layer, a first conductivity type ZnO-based semiconductor current blocking layer, and a semiconductor growth layer including an optical resonator, wherein a pair of device end faces constituting the optical resonator are provided. Wherein the semiconductor growth layer portion has a mirror-like surface parallel to each other, and the substrate portion has a rough surface at a pair of device end faces constituting the optical resonator. I do. In particular, this semiconductor light emitting device can be applied to a semiconductor laser device.
In a semiconductor laser device, the end face of the semiconductor growth layer portion is made to be a mirror surface, so that the end face of the waveguide including the active layer functions as an optical resonator. Can be reflected irregularly, and an increase in noise due to fluctuation can be avoided.
[0023]
In this specification, a layer that controls light emission in a semiconductor light emitting device is referred to as a “light emitting layer”, but in the case of a semiconductor laser device, the term “active layer” may be used in the same sense. However, since the functions of the two are substantially the same, no distinction is made.
[0024]
In the semiconductor light emitting device of the present invention, the substrate has a property of transmitting emitted light. When the substrate has a light-transmitting property, light emitted inside the element and incident on the substrate can be extracted outside the element without being absorbed. Also, in a semiconductor laser device, noise is reduced because the substrate does not absorb return light and generate carriers.
[0025]
In the semiconductor light emitting device of the present invention, the substrate is a ZnO single crystal.
If the substrate is a ZnO single crystal, the substrate has excellent affinity with the ZnO-based semiconductor layer grown thereon, and the crystallinity is improved. In addition, it is excellent in processability such as mirror surface formation and rough surface formation and cleavage, and has a clear advantage over a substrate such as sapphire which is difficult to cleave or process.
[0026]
Further, the present invention also provides a method for manufacturing a semiconductor light emitting device suitable for manufacturing the above semiconductor light emitting device.
In a first aspect, the present invention provides a method of forming a ZnO-based semiconductor growth layer on a substrate by crystal growth, and using a method of ion milling, FIB etching, or reactive ion etching to define the trench. Forming a groove extending from the surface of the semiconductor growth layer to the inside of the substrate so that the side surface of the growth layer becomes mirror-like; and dicing along the groove so that the side surface of the substrate becomes rough. And a step of isolating the element by performing the method.
[0027]
It is difficult for an oxide semiconductor to form a mirror surface with excellent flatness and verticality by wet etching using a chemical solution. However, by applying dry etching such as the ion milling described above, anisotropic etching excellent in flatness and perpendicularity can be realized, and the control of the etching depth is easy. In addition, since the etched end face is less damaged, the element does not deteriorate.
On the other hand, when the element is mechanically separated by dicing, the end face is easily roughened.
Therefore, a light emitting device having a mirror surface on the growth layer side and a rough surface on the substrate side can be easily manufactured.
[0028]
In a second aspect, the present invention defines the trench by crystal-growing a ZnO-based semiconductor growth layer on a substrate and dicing the substrate from the back surface where the semiconductor growth layer is not formed. Forming a groove having a depth not exceeding the thickness of the substrate so that the side surface of the substrate becomes rough; and forming a groove along the groove so that the side surface of the semiconductor growth layer becomes mirror-like. Cleaving the device to separate the device.
Although element separation by cleavage cannot control the depth, it has the best side surface flatness and extremely little damage. Therefore, first, a groove having a rough side surface is formed by dicing the substrate portion, and then cleavage is performed from the groove portion to separate elements, so that the growth layer side surface is a mirror surface and the substrate side surface is a rough surface. Can be easily manufactured.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment in which the semiconductor light emitting device of the present invention is applied to a light emitting diode device and a semiconductor laser device will be specifically described below with reference to the drawings.
First embodiment
The semiconductor light-emitting device according to the first embodiment of the present invention includes at least a first conductive type ZnO-based semiconductor clad layer, a ZnO-based semiconductor light-emitting layer, a second conductive type ZnO-based semiconductor clad layer, and a second conductive type. A semiconductor light emitting device in which a semiconductor growth layer including a conductive type ZnO-based semiconductor contact layer is formed, wherein the semiconductor growth layer portion has a mirror-like surface on the device side surface and the substrate portion has a rough surface on the device side surface. A light emitting diode element having a surface.
[0030]
In the light-emitting diode device of the present invention, light emitted from the light-emitting layer is hardly totally reflected on the side surface of the growth layer and is easily extracted to the outside. Since the light incident on the substrate has a low light extraction efficiency, roughening the side surface makes it easier to extract light out of the element by irregular reflection.
That is, the light emitted from the light emitting layer is incident on the side surface of the growth layer near the light emitting layer at a small incident angle. Therefore, in order to improve the light extraction efficiency to the outside, the side surface should be a mirror surface. On the other hand, the light is incident on the substrate part far from the light-emitting layer at a large incident angle, and the incident light easily causes total reflection. Therefore, to improve the light extraction efficiency, the side surface of the substrate part must be roughened. It is effective to cause irregular reflection.
[0031]
FIG. 1 shows a perspective view (A) and a sectional view (B) of the light emitting diode element 1. The light emitting diode element 1 includes an n-type ZnO buffer layer 102, an n-type MgZnO cladding layer 103, a non-doped quantum well light-emitting layer 104, and a p-type MgZnO cladding layer 105 on an n-type ZnO single crystal substrate 101 having a zinc surface as a main surface. And a p-type ZnO contact layer 106.
[0032]
The quantum well light emitting layer 104 has a multi-well structure in which one or a plurality of barrier layers and one or a plurality of CdZnO well layers are alternately stacked.
Under the ZnO substrate 101, an n-type ohmic electrode 107 is formed.
On the entire main surface of the p-type ZnO contact layer 106, a p-type ohmic electrode 108 that transmits light emitted from the light-emitting layer is laminated. Further, on the translucent p-type ohmic electrode 108, an Au pad electrode 109 for bonding is formed with a smaller area than the translucent ohmic electrode 108.
[0033]
Furthermore, the four side surfaces of the n-type ZnO single crystal substrate 101 are roughened by dicing. On the other hand, the four side surfaces of the semiconductor growth layer from the n-type ZnO buffer layer 102 to the p-type ZnO contact layer 106 are etched surfaces having excellent flatness.
[0034]
Hereinafter, other configurations for maximizing the effects of the present invention will be described, but in other embodiments, any combination can be used.
[0035]
In the semiconductor light emitting device of the present invention, the material of the substrate 101 may be sapphire, spinel, LiGaO₂Or a conductive substrate such as SiC or GaN.
When an insulating substrate is used, the n-type ZnO buffer layer 102 may be exposed at an appropriate area when forming the groove by etching, and the n-type ohmic electrode 107 may be formed thereon.
[0036]
However, in order to maximize the high luminous efficiency, which is the effect of the present invention, (1) a lattice-matched substrate having an in-plane lattice constant difference with ZnO of 3% or less and having excellent crystallinity of the grown layer. It is preferable to use a substrate that can reduce defects serving as non-emission centers, (2) has a low absorption coefficient corresponding to the emission wavelength, and (3) is conductive and can form an electrode on the back surface. A substrate made of ZnO single crystal is most preferable because it satisfies all the above conditions. The ZnO substrate is perfectly lattice-matched with the ZnO-based semiconductor light emitting device epitaxially grown thereon, and has a higher affinity than using a heterogeneous substrate. Thus, a light-emitting element having good crystallinity and extremely few non-light-emission centers can be manufactured.
[0037]
The use of a zinc surface as the main surface is preferable because the carrier activation rate of the p-type layer is improved and a p-type layer having low resistance is easily obtained.
In addition, it is preferable to form irregularities on the back surface of the substrate by a known method such as polishing or etching and irregularly reflect the emitted light, which improves the light extraction efficiency.
[0038]
As a donor impurity to be doped into the n-type ZnO buffer layer 102 and the n-type MgZnO cladding layer 103, a group III element such as B, Al, Ga, or In may be used because the activation rate in the ZnO-based semiconductor is high. Ga and Al are particularly preferred.
[0039]
The light-emitting layer 104 can have a single structure; however, the light-emitting layer 104 preferably has a multiple quantum well structure because optical gain is improved, carrier confinement efficiency and light emission efficiency are increased, and light emission intensity can be increased. .
In the semiconductor light emitting device of the present invention, the light emitting layer may be doped with impurities irrespective of a single structure or a multiple quantum well structure. By doping the light emitting layer with an impurity, the luminous efficiency can be improved, and the emission wavelength can be adjusted by utilizing transition via the impurity level.
[0040]
As the donor impurity that can be doped into the ZnO-based semiconductor light emitting layer of the first embodiment, for example, one or more group III elements selected from the group consisting of B, Al, Ga, and In can be doped. Further, as the acceptor impurity, for example, one or more group I or V elements selected from the group consisting of Li, Na, Cu, Ag, N, P and As can be doped. Further, as a recombination center for promoting radiative recombination, for example, one or a plurality of group IV elements selected from the group consisting of Si, Ge, C, and Sn can be doped. When the light emitting layer has a multiple quantum well structure, the donor impurity can be doped into the entire quantum well structure. Also, only the well layer or only the barrier layer can be doped. By doping only the well layer, the total amount of doping is reduced and the crystallinity is improved. Also, by doping only the barrier layer, carrier loss is reduced and the threshold is reduced.
[0041]
As an acceptor impurity to be doped into the p-type MgZnO layer 105 and the p-type ZnO contact layer 106, a group I or V element such as Li, Na, Cu, Ag, N, P, As, or the like can be used. N and Ag are preferable because they are easily activated. N is N₂Is particularly preferable because high-concentration doping can be performed while maintaining good crystallinity by a method of irradiating during plasma growth with plasma.
[0042]
For the p-type ohmic electrode 108, a metal material such as Ni, Pt, Pd, and Au can be used. The metal material forms a low-resistance ohmic contact with the p-type ZnO-based semiconductor layer and has excellent adhesion to the ZnO-based semiconductor. Therefore, a light-emitting element with excellent reliability and low operating voltage can be realized. Among them, Ni having low resistance and good adhesion is preferable. An electrode may be formed by alloying a plurality of the metal materials. The p-type ohmic electrode 108 can be directly formed on the p-type MgZnO cladding layer 105. However, since the MgZnO mixed crystal has a lower impurity activation rate than ZnO, the p-type ZnO contact layer 106 is formed. Is preferably formed thereon.
In order to obtain the high luminous efficiency and low operating voltage of the present invention with the maximum effect, the p-type ohmic electrode 108 is formed so as to have a light-transmitting property with respect to the light emitted from the light-emitting layer. It is preferable to improve the extraction efficiency.
Since the transparent conductive film is formed on the entire main surface, the current spread becomes uniform and the external light extraction efficiency is improved. Therefore, an ultraviolet light emitting device having excellent luminous efficiency can be realized.
The thickness that achieves both good ohmic characteristics and high translucency is preferably in the range of 50 to 200 nm, more preferably in the range of 300 to 100 nm.
It is preferable to perform an annealing treatment after the formation of the p-type ohmic electrode 108 because the adhesion is improved and the contact resistance is reduced. In order to obtain an annealing effect without causing defects in the ZnO crystal, the temperature is preferably 300 to 400 ° C. The atmosphere in the annealing process is O₂Or in an air atmosphere;₂Then, on the contrary, the resistance increases.
[0043]
If the pad electrode 109 is formed on a part of the translucent p-type ohmic electrode 108 with a smaller area than the p-type ohmic electrode 108, the mounting process on the lead frame is easy without impairing the effect of the translucent electrode. Is preferable. As a material of the pad electrode 109, a metal material which is easy to bond and does not become a donor impurity even when diffused into a ZnO-based semiconductor is preferable, and Au is particularly preferable.
Another metal layer may be formed between the p-type ohmic electrode 108 and the pad electrode 109 for the purpose of improving adhesion and light reflectivity.
[0044]
For the n-type ohmic electrode 107, a metal material such as Ti, Cr, or Al can be used. Above all, Al with low resistance and low cost or Ti with good adhesion is preferable. An electrode may be formed by alloying a plurality of the metal materials.
Since Al has a high reflectance of blue to ultraviolet light, even if the n-type ohmic electrode 107 is formed on the entire back surface using Al, the light extraction efficiency is high, which is preferable.
Further, the n-type ohmic electrode 107 can be patterned into an arbitrary shape, and the exposed back surface of the substrate can be bonded to a lead frame with a conductive resin such as an Ag paste. Since Ag has a higher reflectance of blue to ultraviolet light than Al, it is also preferable to pattern the n-type ohmic electrode 107.
When the n-type ohmic electrode 107 is patterned, an auxiliary electrode may be formed using a metal material different from that of the n-type ohmic electrode 107 in order to prevent an increase in element resistance. More preferably, a metal having a high light reflectance is used for the auxiliary electrode.
Since the auxiliary electrode increases the contact area with the lead frame, the operating voltage does not increase even if the n-type electrode is patterned. Therefore, an ultraviolet light emitting element with a low operating voltage can be realized.
[0045]
The semiconductor light emitting device of the present invention is manufactured by a crystal growth method such as a molecular beam epitaxy (MBE) method using a solid or gaseous raw material, a laser molecular beam epitaxy (laser MBE) method, and a metal organic chemical vapor deposition (MOCVD) method. be able to.
In the laser MBE method, the composition deviation between the raw material target and the thin film is small, and for example, when ZnO is doped with Ga,₂O₄This is preferable because generation of unintended by-products such as the above can be suppressed.
[0046]
Second embodiment
The second semiconductor light-emitting device according to the present invention comprises, on a substrate, at least a first conductivity type ZnO-based semiconductor clad layer, a ZnO-based semiconductor active layer, a second conductivity-type ZnO-based semiconductor clad layer, and a second conductivity-type ZnO-based semiconductor clad layer. A semiconductor light emitting device in which a ZnO-based semiconductor contact layer, a first conductivity type ZnO-based semiconductor current blocking layer, and a semiconductor growth layer including an optical resonator are formed, wherein a pair of device end faces constituting the optical resonator are provided. A semiconductor laser device wherein a semiconductor growth layer portion has mirror surfaces parallel to each other, and a substrate portion has a rough surface at a pair of device end faces constituting the optical resonator.
In the semiconductor laser device of the present invention, by making the end face of the semiconductor growth layer part a mirror surface, the end face of the waveguide including the active layer functions as an optical resonator, while the end face of the substrate part is made rough. In addition, it is possible to avoid the increase of noise due to the fluctuation by irregularly reflecting the return light.
[0047]
FIG. 3 shows a perspective view (A) of the semiconductor laser element 2 and a side view (B) viewed from a direction parallel to the light emitting end face. The semiconductor laser device 2 includes an n-type ZnO buffer layer 202, an n-type MgZnO cladding layer 203, an n-type ZnO light guide layer 204, and a non-doped quantum well active layer on an n-type ZnO single crystal substrate 201 having a zinc surface as a main surface. 205, a p-type ZnO light guide layer 206, a p-type MgZnO cladding layer 207, and a p-type ZnO contact layer 208.
[0048]
The quantum well active layer 205 has a multi-well structure in which one or a plurality of ZnO barrier layers and one or a plurality of CdZnO well layers are alternately stacked.
A part of the p-type ZnO contact layer 208 and a part of the p-type MgZnO clad layer 207 are etched into a ridge stripe shape, and the n-type MgZnO current block layer 209 buries the side of the ridge stripe.
An n-type ohmic electrode 210 is formed below the ZnO substrate 201, and a p-type ohmic electrode 211 is formed on the p-type ZnO contact layer 208.
The side surface part 201a of the n-type ZnO single crystal substrate 201 on the light emitting end face is roughened by dicing.
[0049]
On the other hand, the light reflecting end face (same as the light emitting end face) forming the optical resonator is formed by forming a groove portion by dicing from the back surface of the substrate and then cleaving the growth layer from the groove portion, and further forming a mirror end surface. MgO layer and SiO₂A dielectric reflection film 212 in which layers are alternately stacked is stacked.
By adjusting the number of layers, the reflectance for light of a specific wavelength can be controlled.
Note that the dielectric reflection film 212 may be formed over the end surface 201a of the ZnO substrate 201 which is roughened.
[0050]
That is, in the semiconductor laser device according to the present invention, the end face of the growth layer near the active layer where the waveguide is formed has a mirror surface with little damage due to cleavage, and thus has no effect on the resonance amplification operation of the laser. In addition, there is no need to form a resist film or process a dielectric film after element isolation, and since a mirror surface and a rough surface can be formed at the element isolation stage, production efficiency is not affected.
In the case of a semiconductor laser device, it is not necessary to separately form a mirror surface and a rough surface on the other pair of side surfaces on which the optical resonator is not formed. Since the length is shortened, it is preferable that the elements are separated by cleavage or dry etching.
[0051]
【Example】
Example 1
This embodiment describes a first semiconductor light emitting device in which the present invention is applied to a light emitting diode device.
FIG. 1 shows a perspective view (A) and a sectional view (B) of the light emitting diode element 1. In this embodiment, 1 × 10 Ga was formed on an n-type ZnO single crystal substrate 101 having a zinc surface as a main surface.¹⁸cm^-3N-type ZnO buffer layer 102 having a thickness of 0.1 μm and a Ga concentration of 1 × 10¹⁸cm^-30.5 μm thick n-type Mg doped at a concentration of_0.1Zn_0.9O cladding layer 103, non-doped quantum well light emitting layer 104, N is 5 × 10¹⁹cm^-30.5 μm thick p-type Mg doped at a concentration of_0.1Zn_0.9O cladding layer 105 and N are 1 × 10²⁰cm^-3The p-type ZnO contact layer 106 having a thickness of 0.3 μm and doped with the above concentration was stacked to fabricate a light emitting diode element 1a.
[0052]
The quantum well light emitting layer 104 is composed of eight ZnO barrier layers having a thickness of 5 nm and Cd having a thickness of 4 nm._0.1Zn_0.9It is formed by alternately stacking seven O-well layers.
Under the ZnO substrate 101, an n-type ohmic electrode 107 in which Al having a thickness of 100 nm is laminated is formed. On the entire main surface of the p-type ZnO contact layer 106, a translucent p-type ohmic electrode 108 having a thickness of 15 nm is laminated, and a 100-nm-thick Au pad electrode for bonding is formed on the p-type ohmic electrode 108. 109 is formed with an area smaller than the ohmic electrode 108.
[0053]
Furthermore, the four side surfaces of the n-type ZnO single crystal substrate 101 are roughened by dicing. On the other hand, the four side surfaces of the semiconductor growth layer from the n-type ZnO buffer layer 102 to the p-type ZnO contact layer 106 are etched surfaces having excellent flatness.
[0054]
The manufacturing method will be described below in order with reference to FIG. FIG. 2 shows the manufacturing process from a cross section.
[0055]
First, an n-type ZnO buffer layer 102 and an n-type Mg_0.1Zn_0.9O cladding layer 103, non-doped quantum well light emitting layer 104, p-type Mg_0.1Zn_0.9After laminating the O clad layer 105 and the p-type ZnO contact layer 106, an n-type Al ohmic electrode 107 is provided on the back surface of the ZnO substrate 101, and a p-type Ni ohmic electrode 108 and an Au pad electrode 109 are sequentially provided on the p-type ZnO contact layer 106. The layers were stacked (FIG. 2A).
Next, the Au pad electrode 109 was processed into a circular shape having a diameter of 80 μm, and a resist mask 110 having a 300 μm square and an interval of 80 μm was formed around the Au pad electrode 109 (FIG. 2B).
[0056]
Next, CF₄And CH₄The growth layer was RIE-etched from the opening of the resist mask in a lattice pattern using the mixed gas of FIG. The etching conditions were an acceleration voltage of 1 kV and a plasma output of 50 W. The side surfaces of the etched growth layer were vertical and flat mirror surfaces.
[0057]
Next, the resist mask was removed by washing, and the bottom surface of the groove formed by RIE was diced to the back surface using a diamond blade having a thickness of 40 μm to separate four sides of the element (FIG. 2D). At this time, the rotation speed of the blade was adjusted so that the side surface of the substrate became rough.
[0058]
After the back surface of the light emitting diode element 1a was attached to the lead frame with a conductive paste, wiring was performed on the pad electrode 109, and resin molding was performed to emit light. As shown in FIG. 4, blue light emission having an emission peak wavelength of 410 nm was obtained. Was done.
[0059]
For comparison, a light emitting diode element 1b was produced and emitted light in the same manner as the light emitting diode element 1a, except that the groove portion was formed by RIE until the bottom surface of the substrate was reached, and all the side surfaces of the light emitting diode element were mirror-finished. The light emission intensity after resin molding was about 60% as compared with the light emitting diode element 1a.
[0060]
Further, a light emitting diode element 1c is produced and light is emitted in the same manner as the light emitting diode element 1a, except that the element is separated only by dicing and the side surfaces of the light emitting diode element are roughened without forming a groove by the RIE method. As a result, the light emission intensity after resin molding was about 70% as compared with the light emitting diode element 1a. In addition, when the device was continuously energized with an operating current of 20 mA, the light emission intensity decreased with the passage of time, and after 20 hours, decreased to 70% immediately after the energization.
[0061]
Such a result was obtained because, by making the side surface of the growth layer portion near the light emitting layer a mirror surface, light emitted at a small incident angle passed through the mirror surface without irregular reflection. It is considered that light extraction efficiency to the outside was improved, and light emission incident at a large incident angle was irregularly reflected by making the side surface of the substrate part rough, so that light extraction efficiency was improved.
[0062]
In this embodiment, the mirror surface on the growth side surface is formed by RIE. However, even if anisotropic etching is performed by another dry etching method such as ion milling or FIB etching, a mirror surface with less damage can be obtained. The same effect as the example is achieved.
[0063]
Example 2
This embodiment describes a second semiconductor light emitting device in which the present invention is applied to a semiconductor laser device.
FIG. 3 shows a perspective view (A) of the semiconductor laser element 2 and a side view (B) viewed from a direction parallel to the light emitting end face. In this embodiment, Ga was placed on an n-type ZnO single crystal substrate 201 having a zinc surface as a main surface by 1 × 10¹⁸cm^-3N-type ZnO buffer layer 202 having a thickness of 0.1 μm and a Ga concentration of 3 × 10¹⁸cm^-3N-type Mg doped at a concentration of 1 μm_0.1Zn_0.9O cladding layer 203, Ga is 5 × 10¹⁷cm^-330 nm thick n-type ZnO light guide layer 204, non-doped quantum well active layer 205, and N¹⁸cm^-330 nm thick p-type ZnO light guide layer 206 doped with a concentration of¹⁹cm^-31.2 μm thick p-type Mg doped at a concentration of_0.1Zn_0.9O cladding layer 207 and N²⁰cm^-3The p-type ZnO contact layer 208 having a thickness of 0.5 μm and doped at a concentration of 0.5 μm was stacked to fabricate a semiconductor laser device 2 a.
[0064]
The quantum well active layer 205 is composed of two 5 nm thick ZnO barrier layers and 6 nm thick Cd_0.1Zn_0.9It is formed by alternately stacking three O well layers.
p-type ZnO contact layer 208 and p-type Mg_0.1Zn_0.9A part of the O-clad layer 207 is etched into a ridge stripe shape, and Ga is 3 × 10¹⁸cm^-3-Type Mg doped at a concentration of_0.2Zn_0.8The ridge stripe side surface is buried by the O current block layer 209.
An n-type ohmic electrode 210 is formed below the ZnO substrate 201, and a p-type ohmic electrode 211 is formed on the p-type ZnO contact layer 208.
The side surface part 201a of the n-type ZnO single crystal substrate 201 on the light emitting end face is roughened by dicing.
[0065]
On the other hand, the light reflection end face (same as the light emission end face) forming the optical resonator is formed by forming a groove by dicing from the back surface of the substrate and then cleaving the growth layer from the groove, and furthermore, the mirror end face is formed. On both front and rear surfaces, a 60 nm thick MgO layer and a 70 nm thick SiO₂The dielectric reflective film 212 in which the layers are alternately laminated is laminated, and the number of laminated layers is adjusted so that the reflectance with respect to light having a wavelength of 410 nm is 20%. Note that the dielectric reflection film 212 may be formed over the end surface portion 201a of the ZnO substrate 201 which has a rough surface.
[0066]
When a current was applied to the semiconductor laser element 2a, blue oscillation light having a wavelength of 405 nm was obtained from the end face as shown in FIG.
Further, the semiconductor laser element 2a was mounted on the pickup, and the number of read errors before error correction of the optical disk was measured. As a result, the number was 30 / sec.
[0067]
On the other hand, for comparison, the semiconductor laser device 2a was fabricated in the same manner as the semiconductor laser device 2a except that a shallow scribing groove was formed on the back surface of the ZnO substrate by scribing instead of dicing, and the substrate end surface was mirror-finished by cleaving from the scribing groove portion. Laser element 2b was produced. This semiconductor laser element 2b was mounted on a pickup, and the number of read errors before error correction of the optical disk was measured as in the case of the semiconductor laser element 2a. The result was 200 / sec.
[0068]
The above results were obtained because in the semiconductor laser element 2a, the end surface of the substrate portion where the return light was focused was roughened, so that it was possible to suppress the return light from re-reflecting and causing undulation in the tracking signal. it is conceivable that.
[0069]
【The invention's effect】
According to the semiconductor light emitting device of the present invention, the semiconductor light emitting device including the semiconductor layer grown on the substrate has a flat mirror surface on the side surface of the growth layer and has a rough surface portion on the side surface of the substrate. Therefore, both light extraction and scattering reflection of the light emitting element are controlled, and a light emitting element with excellent luminous efficiency and reliability can be realized.
According to the method for manufacturing a semiconductor light emitting device of the present invention, a step of crystal-growing a ZnO-based semiconductor layer on a substrate, a step of performing dry etching or cleavage so that a side surface of the semiconductor growth layer has a mirror surface, Includes the step of separating elements by dicing so that the side surface has a rough surface, so that anisotropic etching with excellent flatness and verticality can provide a mirror end surface with less damage, and at the same time, easily roughen the substrate end surface Obtainable.
[Brief description of the drawings]
FIG. 1 is a perspective view (A) and a cross-sectional view (B) showing a semiconductor light emitting device (light emitting diode device) according to a first embodiment of the present invention.
FIG. 2 is a schematic view illustrating a manufacturing process of the semiconductor light emitting device according to the first embodiment of the present invention.
FIG. 3 is a perspective view (A) and a side view (B) showing a semiconductor light emitting device (semiconductor laser device) according to a second embodiment of the present invention.
FIG. 4 is an emission spectrum of the semiconductor light emitting device (light emitting diode device) according to the first embodiment of the present invention.
FIG. 5 is an oscillation spectrum of a semiconductor light emitting device (semiconductor laser device) according to a second embodiment of the present invention.
[Explanation of symbols]
1 ... light emitting diode element
101 ... ZnO substrate,
102 ... n-type ZnO buffer layer,
103 ... n-type MgZnO cladding layer
104 ・ ・ ・ Quantum well active layer,
105 ... p-type MgZnO cladding layer,
106 ... p-type ZnO contact layer,
107 ... n-type ohmic electrode,
108 ··· p-type ohmic electrode,
109 ... pad electrode,
110 ... resist mask,
2 ... Semiconductor laser device,
201: ZnO substrate,
201a: Substrate side rough surface,
202 ... n-type ZnO buffer layer,
203 ... n-type MgZnO cladding layer,
204 ... n-type ZnO light guide layer,
205 ・ ・ ・ Quantum well active layer,
206 ... p-type ZnO light guide layer,
207 ... p-type MgZnO cladding layer,
208 ... p-type ZnO contact layer,
209... N-type MgZnO current blocking layer,
210 ... n-type ohmic electrode,
211 ... p-type ohmic electrode,
212: dielectric reflection film.

Claims (7)

A semiconductor light emitting device having a semiconductor growth layer formed on a substrate, wherein the side surface of the substrate is rough, and the side surface of the semiconductor growth layer is a flat mirror surface. A semiconductor growth layer including at least a first conductivity type ZnO-based semiconductor clad layer, a ZnO-based semiconductor light-emitting layer, a second conductivity-type ZnO-based semiconductor clad layer, and a second conductivity-type ZnO-based semiconductor contact layer is formed on a substrate. A semiconductor light emitting device formed, wherein a semiconductor growth layer portion has a mirror-like surface on a device side surface, and a substrate portion has a rough surface on a device side surface. On a substrate, at least a first conductivity type ZnO-based semiconductor clad layer, a ZnO-based semiconductor active layer, a second conductivity-type ZnO-based semiconductor clad layer, a second conductivity-type ZnO-based semiconductor contact layer, and a first conductivity-type ZnO-based semiconductor contact layer. A semiconductor light emitting device having a ZnO-based semiconductor current block layer and a semiconductor growth layer including an optical resonator formed thereon, wherein the semiconductor growth layer portions are mirror-shaped parallel to each other at a pair of element end faces constituting the optical resonator. A semiconductor light-emitting device having a surface and a substrate having a rough surface at a pair of device end faces constituting the optical resonator. The semiconductor light emitting device according to claim 1, wherein the substrate has a property of transmitting light. 5. The semiconductor light emitting device according to claim 4, wherein said substrate is a ZnO single crystal. A step of growing a crystal of a ZnO-based semiconductor growth layer on a substrate, and using a method of ion milling, FIB etching or reactive ion etching so that the side surface of the semiconductor growth layer defining the groove becomes mirror-like. Forming a groove extending from the surface of the semiconductor growth layer to the inside of the substrate; andseparating elements by dicing along the groove so that the side surface of the substrate becomes rough. And a method for manufacturing a semiconductor light emitting device. A step of growing a ZnO-based semiconductor growth layer on the substrate and dicing the substrate from the back surface where the semiconductor growth layer is not formed, so that the side surface of the substrate defining the groove becomes rough. Forming a groove having a depth not exceeding the thickness of the substrate, and cleaving along the groove so that the side surface of the semiconductor growth layer becomes mirror-like, thereby isolating the element. A method for manufacturing a semiconductor light emitting device comprising:

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