JP3897448B2 - Nitride semiconductor light emitting device - Google Patents

Nitride semiconductor light emitting device Download PDF

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JP3897448B2
JP3897448B2 JP11654698A JP11654698A JP3897448B2 JP 3897448 B2 JP3897448 B2 JP 3897448B2 JP 11654698 A JP11654698 A JP 11654698A JP 11654698 A JP11654698 A JP 11654698A JP 3897448 B2 JP3897448 B2 JP 3897448B2
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nitride semiconductor
semiconductor layer
layer
cm
carbon
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JPH11307812A (en
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靖 森岡
雅俊 阿部
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日亜化学工業株式会社
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Description

[0001]
[Industrial application fields]
The present invention relates to a nitride semiconductor (InXAlYGa1-XYN, 0.ltoreq.X, 0.ltoreq.Y, X + Y.ltoreq.1), and a nitride semiconductor light-emitting device used for a light-emitting device such as a light-emitting diode device and a laser diode device. The present invention relates to a nitride semiconductor light emitting device having a reduced value.
[0002]
[Prior art]
Nitride semiconductors have already been put to practical use in various light sources such as full-color LED displays, traffic signal lights, and image scanner light sources as high-luminance pure green light-emitting LEDs and blue LEDs. These LED elements basically have a buffer layer made of GaN on a sapphire substrate, an n-side contact layer made of Si-doped GaN, an active layer made of InGaN having a single quantum well structure, and a p-type made of Mg-doped AlGaN. It has a structure in which a side cladding layer and a p-side contact layer made of Mg-doped GaN are sequentially stacked. At 20 mA, a blue LED having an emission wavelength of 450 nm is 5 mW, an external quantum efficiency is 9.1%, and a green color is 520 nm. The LED exhibits very excellent characteristics of 3 mW and external quantum efficiency of 6.3%.
[0003]
Japanese Patent Laid-Open No. 10-4210 discloses a low impurity addition amount in order from the side closer to the substrate of the n layer in order to improve the crystallinity of each layer of the light emitting element and improve the light emission luminance and the light emission efficiency. It is described that a concentration impurity layer and a high concentration impurity layer are formed thereon. In this technique, the crystallinity is improved by using a low-concentration impurity layer, and the crystallinity of a high-concentration impurity layer, particularly a light-emitting layer, which is stacked and grown on this layer is improved. It is described that luminous efficiency is improved.
[0004]
[Problems to be solved by the invention]
However, the nitride semiconductors already in practical use for traffic signal lights and the like as described above have been put to practical use as described above, but in order to use the LEDs in, for example, illumination light sources, outdoor displays exposed to direct sunlight, etc. Is not a satisfactory output, and further improvements in output are required. Further, the LED element has a Vf of nearly 3.6 V at 20 mA, and it is desired to further lower the Vf in order to reduce the amount of heat generated by such an element and further improve the reliability.
[0005]
Furthermore, in the technique disclosed in Japanese Patent Laid-Open No. 10-4210, since the n-type impurity concentration of the layer for forming the n-electrode is increased in order to reduce the resistivity, a high-concentration impurity layer is formed on the low-concentration impurity layer. Even if formed, the crystallinity cannot be made sufficiently satisfactory. In addition, in order to improve the reliability of the light emitting element, it is desired to further reduce Vf and the threshold value. However, it is difficult to sufficiently reduce the resistivity with the n electrode, and Vf and threshold value are difficult to reduce. Cannot be reduced sufficiently. Further, when the amount of impurities added is increased for the purpose of reducing the resistivity, the crystallinity of the nitride semiconductor layer is lowered, and there is a problem that light emission efficiency and the like are easily lowered.
[0006]
Accordingly, an object of the present invention is mainly to improve the output of nitride semiconductor light emitting devices such as LEDs and LDs, and to further improve device reliability by lowering Vf and threshold values.
[0007]
[Means for Solving the Problems]
  That is, the present inventionThe nitride semiconductor light emitting device according to the claims can achieve the object of the present invention by the following configurations (1) to (4).
(1) Between the substrate and the active layer, an undoped first nitride semiconductor layer in order from the substrate side, an n-conductivity-type second nitride semiconductor layer containing carbon and Si as an n-type impurity, The carbon concentration of the first nitride semiconductor layer is 7 × 10 16 / Cm 3 The carbon concentration of the second nitride semiconductor layer is 2 × 10 17 / Cm 3 ~ 1x10 20 / Cm 3 Further, an n-electrode is formed on the second nitride semiconductor layer, and an undoped third nitride semiconductor layer is formed between the second nitride semiconductor layer and the active layer. And a nitride semiconductor light emitting device.
(2) The resistivity of the second nitride semiconductor layer is 1 × 10 -5 Ω · cm or more, 8 × 10 -3 The nitride semiconductor light emitting device according to (1), wherein the nitride semiconductor light emitting device is less than Ω · cm.
(3) A buffer layer grown at a lower temperature than the n-conductivity-type nitride semiconductor layer is provided between the substrate and the n-conductivity-type nitride semiconductor layer. The nitride semiconductor light-emitting device according to 2).
  (4) The nitride semiconductor light-emitting element according to any one of (1) to (3), wherein a film thickness of the third nitride semiconductor layer is 0.5 μm or less.
  Moreover, in another form of this invention, the objective of this invention can be achieved by the structure of following (1)-(8).
  (1) An n-conductivity-type second nitride semiconductor containing an undoped first nitride semiconductor layer and carbon or carbon and an n-type impurity in that order from the substrate side between the substrate and the active layer. And the carbon of the first nitride semiconductor layer is 8 × 10 816/ Cm3The carbon content of the second nitride semiconductor layer is 2 × 1017/ Cm3A nitride semiconductor light emitting device comprising the above, and further comprising an n-electrode formed on the second nitride semiconductor layer.
  (2) The nitride according to (1), wherein an undoped third nitride semiconductor layer is formed on the second nitride semiconductor layer in the nitride semiconductor light emitting device. Semiconductor light emitting device.
  (3) The nitride semiconductor light-emitting element according to (1) or (2), wherein the n-type impurity is at least one of Si, Ge, and Sn.
  (4) The resistivity of the second nitride semiconductor layer is 1 × 10-5The nitride semiconductor light-emitting element according to any one of (1) to (3), wherein the nitride semiconductor light-emitting element has a resistance of Ω · cm to 0.2 Ω · cm.
  (5) The nitride semiconductor light-emitting element according to any one of (1) to (4), wherein the second nitride semiconductor layer contains Si as an n-type impurity.
  (6) The resistivity of the second nitride semiconductor layer containing carbon and Si is 8 × 10.-3The nitride semiconductor light-emitting element according to any one of (1) to (5), wherein the nitride semiconductor light-emitting element is less than Ω · cm.
  (7) The above-mentioned (1) to (1), wherein a buffer layer is grown between the substrate and the n-conductivity-type nitride semiconductor layer at a lower temperature than the n-conductivity-type nitride semiconductor layer. 6. The nitride semiconductor light emitting device according to any one of 6).
  (8) The nitride semiconductor light emitting element according to any one of (2) to (7), wherein a film thickness of the third nitride semiconductor layer is 0.5 μm or less.
[0008]
That is, in the present invention, when forming the second nitride semiconductor layer on which the n-electrode is formed on the undoped first nitride semiconductor layer having good crystallinity, carbon or carbon and n-type impurities are added. By including, the second nitride semiconductor layer having a low resistivity is formed without impairing the crystallinity of the second nitride semiconductor layer despite containing carbon or an n-type impurity. Can do. With such a configuration of the present invention, the second nitride semiconductor layer having good crystallinity and low resistivity can be formed, and thereby the object of the present invention can be achieved.
[0009]
In the prior art, in order to reduce the resistivity of the n-type layer, the resistivity was adjusted by adding an n-type impurity. However, in order to obtain a desired resistivity, a considerable amount of n-type impurity is contained. Therefore, the crystallinity of the nitride semiconductor tends to decrease in proportion to the concentration of impurities contained. The decrease in crystallinity tends to adversely affect various characteristics of the device.
[0010]
Conventionally, as a technique in which the nitride semiconductor layer constituting the element contains carbon or the concentration of carbon is specified, for example, the following publications can be cited.
First, in Japanese Patent Laid-Open No. 5-243153, by adjusting the partial pressure of a carbon-containing compound during the growth of a nitride semiconductor thin film, the carbon concentration in the nitride semiconductor thin film is lowered to improve the device performance by carbon. It describes that adverse effects are prevented and the characteristics of the device are improved. Next, in Japanese Patent Laid-Open No. 8-316141, an n-type dopant is doped with a specific hydrocarbon compound, and the carbon concentration in the semiconductor layer is set to 8 × 10 8.16cm-3It is described below that carbon contamination can be suppressed and electrical characteristics such as improvement of electron mobility are improved. Japanese Patent Application Laid-Open No. 9-92983 discloses a carbon layer on the electrode formation surface of the n layer in order to reduce the concentration of a sufficient donor property level of the n layer and to make the electrode characteristics of the n layer have good ohmic properties. In order to achieve a layer structure in which the concentration is low and the layer is distributed highly near the substrate, it is described that the structure of the resistance heating body is improved to prevent an increase in the carbon concentration accompanying the deterioration of the resistance heating body.
However, these publications describe improving the characteristics of the device by reducing the carbon concentration, or improving the ohmic contact by reducing the carbon concentration on the surface of the layer forming the n-electrode. There is no description suggesting that the device characteristics are improved by intentionally increasing the concentration. Further, carbon mixed in the nitride semiconductor layer for the reason described in the above publication does not show an effect of improving the crystallinity of the nitride semiconductor layer, suggesting that the crystallinity is lowered by carbon. ing.
[0011]
On the other hand, in the present invention, in order to reduce the resistivity of the second nitride semiconductor layer, carbon (carbon) is intentionally added so that a preferable ohmic contact with the n electrode can be obtained. The resistivity can be reduced, and even when carbon is added, the crystallinity is improved more than before even when the amount of the n-type impurity added is the same level as before, and the n-type impurity is added. Since the resistivity can be reduced even without it, the resistivity can be reduced without deteriorating the crystallinity of the second nitride semiconductor layer. Furthermore, since the second nitride semiconductor layer is formed after the undoped first nitride semiconductor layer is formed, the crystallinity of the second nitride semiconductor layer is likely to be improved. Furthermore, the crystallinity of other layers constituting the element formed on the second nitride semiconductor layer, such as an active layer, is also improved. Thus, by forming the second nitride semiconductor layer having low resistivity and good crystallinity, it is possible to improve the light emission efficiency and output, and to lower Vf and the threshold value.
Furthermore, in the present invention, a more preferable result can be obtained by forming the third nitride semiconductor layer on the second nitride semiconductor layer.
[0012]
In the present invention, an undoped nitride semiconductor layer refers to a nitride semiconductor layer that is not intentionally doped with impurities. For example, impurities contained in raw materials, contamination in the reaction apparatus, and other layers intentionally doped with impurities. A layer in which impurities are mixed by unintentional diffusion from the layer and a layer which can be regarded as substantially undoped by a small amount of doping (for example, resistivity 3 × 10-1(Ω · cm or more) is also defined as undoped in the present invention. In the present invention, the fact that carbon or n-type impurities are contained in the nitride semiconductor layer may be indicated as addition or dope.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
The nitride semiconductor light emitting device of the present invention (sometimes simply referred to as a light emitting device) includes an undoped first nitride semiconductor layer and carbon or carbon in order from the substrate side between the substrate and the active layer. And at least an n-conductivity-type second nitride semiconductor layer doped with n-type impurities, and an n-electrode is formed on the second nitride semiconductor layer. In the present invention, as described above, by doping carbon, the crystallinity is improved even when the amount of n-type impurities added is similar to the conventional amount, and the resistivity is reduced even when the amount of added n-type impurities is reduced. Since it is sufficiently lowered, the crystallinity of the second nitride semiconductor layer is improved. Furthermore, the ohmic contact is improved by forming an n-electrode on the second nitride semiconductor layer doped with carbon. Further, when the resistivity is lowered, Vf and the threshold value are lowered, and a light emitting element with improved reliability can be obtained. Furthermore, since the crystallinity is good even when the second nitride semiconductor layer has a low resistivity, a nitride semiconductor layer (for example, an active layer, a light-emitting layer, a p-conductivity type nitride) grown on the n-type layer is grown. The crystallinity of the semiconductor layer or the like is also improved, and the output and light emission efficiency can be improved.
In the present invention, in addition to the first and second nitride semiconductor layers, one or more n-conductivity type nitride semiconductor layers (n-type layers) and / or undoped layers are formed between the substrate and the active layer. May be.
[0014]
In the present invention, the layer other than the first and second nitride semiconductor layers formed between the substrate and the active layer is preferably an undoped layer. As an undoped layer, it is preferable to form an undoped third nitride semiconductor layer on the second nitride semiconductor layer before forming the active layer. Since the third nitride semiconductor layer is undoped, it is better to form the active layer after forming the third nitride semiconductor layer than to form the active layer directly on the second nitride semiconductor layer. The crystallinity of the active layer is favorable, which is preferable.
[0015]
Hereinafter, the first to third nitride semiconductor layers will be described in more detail.
The first to third nitride semiconductor layers are grown by appropriately adjusting the growth temperature depending on the composition of the layers. For example, the first to third nitride semiconductor layers are grown at a temperature higher than 900 ° C. and lower than 1200 ° C.XAlYGa1-XYN (0 ≦ X, 0 ≦ Y, X + Y ≦ 1), the composition of which is not particularly limited, but preferably GaN, Al with a Y value of 0.2 or lessYGa1-YIn with N or X value of 0.1 or lessXGa1-XWhen N, a nitride semiconductor layer with few crystal defects is easily obtained. When InGaN is grown, when a nitride semiconductor containing Al is grown thereon, cracks can be prevented from entering into the nitride semiconductor layer containing Al. Further, when the third nitride semiconductor layer is composed of an InGaN composition, it is preferably grown at 800 ° C. to 1100 ° C.
When the second nitride semiconductor layer is grown from a single nitride semiconductor, the first nitride semiconductor layer, the second nitride semiconductor layer, and the third nitride semiconductor layer have the same composition. It is desirable to grow a nitride semiconductor.
[0016]
In the present invention, when the first nitride semiconductor layer is undoped, the crystallinity of the second nitride semiconductor layer doped with carbon grown on the first nitride semiconductor layer is improved. Can be preferable. If the first nitride semiconductor layer is intentionally doped with an n-type impurity, the crystallinity deteriorates and it is difficult to grow the second nitride semiconductor layer with good crystallinity.
Further, the thickness of the first nitride semiconductor layer is not particularly limited. For example, when a buffer layer is formed on the substrate, the first nitride semiconductor layer is grown to be thicker than the buffer layer, specifically, 0.1 μm. The film is grown with a film thickness of 20 μm or less. It is preferable that the film thickness is within this range from the viewpoint of obtaining good crystallinity. Since the first nitride semiconductor layer is an undoped layer, the resistivity is greater than 0.1 Ω · cm.
[0017]
In the present invention, it is preferable that a buffer layer is grown on the substrate at a low temperature before the first nitride semiconductor layer is grown, and the first nitride semiconductor layer is grown thereon. As the buffer layer, AlN, GaN, AlGaN, InGaN or the like is used. The buffer layer is grown at a temperature of 200 ° C. or more and 900 ° C. or less with a film thickness of 10 Å to 0.5 μm. This buffer layer is formed to alleviate the lattice mismatch between the nitride semiconductor and the substrate different from the nitride semiconductor, and is preferable for preventing the occurrence of crystal defects. Further, for example, a layer made of a semiconductor different from a nitride semiconductor such as ZnO may be used as the buffer layer.
Here, since the first nitride semiconductor layer is a layer grown at a higher temperature than the buffer layer, it is distinguished from the buffer layer even if it is undoped.
[0018]
In the present invention, the second nitride semiconductor layer becomes a contact layer for forming an n electrode doped with carbon or carbon and an n-type impurity and having a low resistivity and a high carrier concentration.
The second nitride semiconductor layer is formed as a single layer, or is formed by laminating two types of nitride semiconductor layers having different band gap energies, or by laminating nitride semiconductor layers having the same composition. A superlattice structure may be used. When the superlattice layer is used, the mobility of the second nitride semiconductor layer is increased and the resistivity is further lowered, so that an element with particularly high luminous efficiency can be realized. In the case of a superlattice structure, the thickness of the nitride semiconductor layer constituting the superlattice is adjusted to 100 angstroms or less, more preferably 70 angstroms or less, and most preferably 50 angstroms or less. In the case of a superlattice structure, the nitride semiconductor layer constituting the superlattice may be modulation-doped with Si, Ge, Sn, or the like.
Modulation doping means that the nitride semiconductor layers constituting the superlattice layer have different impurity concentrations, and in this case, one of the layers may be undoped, that is, undoped. Preferably, the second nitride semiconductor layer has a superlattice structure in which layers having different band gap energies are laminated, and it is desirable that one of the nitride semiconductor layers is doped with a large amount of n-type impurity, The semiconductor layer is preferably undoped. In the case of modulation doping, the impurity concentration difference is desirably one digit or more.
When the second nitride semiconductor layer is a superlattice as described above, the addition of carbon and n-type impurities is performed by first uniformly doping carbon into each layer of the superlattice and modulatingly doping only n-type impurities, or The n-type impurity is similarly doped by modulation.
[0019]
In the present invention, the n-type impurity added to the second nitride semiconductor layer is not particularly limited as long as it becomes an n-type impurity, but is preferably a Group 4 element, more preferably Si, Ge, and Sn. One or more of these can be used, and more preferably Si. When the n-type impurity is added to the second nitride semiconductor layer, the doping amount (concentration) of the n-type impurity is 2 × 1018cm-3~ 8x1018cm-3, Preferably 3 × 1018cm-3~ 7 × 1018cm-3, More preferably 4 × 1018cm-3~ 6.5 × 1018cm-3It is. This range is preferable in terms of obtaining good crystallinity and low resistivity.
[0020]
In the present invention, the doping amount (concentration) of carbon in the second nitride semiconductor layer is 2 × 1017/ CmThree~ 1x1020/ CmThree, Preferably 2 × 1017/ CmThree~ 1x1019/ CmThree, More preferably 2 × 1017/ CmThree~ 1x1018/ CmThreeIt is. When the carbon doping amount is within this range, the resistivity can be sufficiently lowered without impairing the crystallinity of the second nitride semiconductor layer.
The method for adjusting the carbon doping amount to the above range is not particularly limited, but when growing the second nitride semiconductor made of GaN or the like, for example, using a raw material containing carbon as a reaction gas, a carbon-containing reaction is performed. For example, a method of growing a nitride semiconductor by increasing the gas ratio may be used. As a specific example, when only carbon is first added to the second nitride semiconductor layer, for example, ammonia (NHThree) Is changed to a compound containing carbon, such as dimethylamine, or ammonia and dimethylamine are supplied simultaneously. In addition to adding carbon, an n-type impurity is added to the second nitride semiconductor layer by using a compound containing carbon as a gas serving as a supply source of the n-type impurity. As described above, there are several methods for doping carbon, but these methods may be combined.
[0021]
The resistivity of the second nitride semiconductor layer is desirably as small as possible in order to obtain a preferable ohmic contact with the n-electrode material, and is adjusted by carbon or carbon and n-type impurities. Specifically, the resistivity is 1 × 10-FiveΩ · cm to 0.2Ω · cm, preferably 7 × 10-2Ω · cm or less, more preferably 2 × 10-2Ω · cm or less. When the resistivity is within this range, preferable ohmic contact with the n-electrode material can be obtained, and Vf can be lowered. In addition, the crystallinity of the n-type layer of the present invention is such that, by adding carbon, the resistivity can be sufficiently lowered even when the amount of n-type impurities added is reduced, and the crystallinity is improved. Compared with the semiconductor layer, the reliability of the element is improved.
[0022]
In the present invention, when the second nitride semiconductor layer uses Si as an n-type impurity and is doped with Si and carbon to adjust the resistivity of the second nitride semiconductor layer, the resistivity is 8 × 10-3Less than Ω · cm, preferably 6 × 10-3Ω · cm or less, more preferably 4 × 10-3Ω · cm or less, and the lower limit is not particularly limited, but 1 × 10-FiveIt is preferable to be Ω · cm or more. It is preferable that the resistivity when the n-type impurity is Si is in the above range because good ohmic contact, Vf and threshold value can be lowered.
When the second nitride semiconductor layer is doped with carbon and Si, the resistivity is 8 × 10-3When it is Ω · cm or more, Vf tends not to decrease so much. When the second nitride semiconductor layer is formed as a single layer, the lower limit is 1 × 10-3On the other hand, when the second nitride semiconductor layer is formed of a superlattice layer, 1 × 10-FiveIt is desirable to adjust to Ω · cm or more. The superlattice layer refers to a multilayer structure in which nitride semiconductor layers having a thickness of 100 angstroms or less, more preferably 70 angstroms, and most preferably 50 angstroms or less are stacked. If the resistance is lower than the lower limit value, the amount of impurities such as Si, Ge, Sn, etc. increases so much that the crystallinity of the nitride semiconductor tends to deteriorate.
The carrier concentration of the second nitride semiconductor layer is 3 × 1018/ CmThreeTend to be bigger.
The film thickness of the second nitride semiconductor layer is not particularly limited, but is preferably a layer having a thickness of 1 μm or more and 20 μm or less because it is a layer for forming an n-electrode.
[0023]
In the present invention, before the active layer is formed on the second nitride semiconductor layer, the third nitride semiconductor layer to be formed is undoped and thus becomes a layer with good crystallinity. When the active layer is grown through the third nitride semiconductor layer having good crystallinity, the third nitride semiconductor layer acts as a buffer layer and is grown on the third nitride semiconductor layer. The crystallinity of the active layer and the like is improved. When an active layer, a clad layer, or the like is grown directly on the second nitride semiconductor layer without forming the third nitride semiconductor layer, the second nitride semiconductor layer becomes carbon or carbon and n. Since the type impurity is doped, the crystallinity is slightly inferior to that of the undoped layer. Therefore, the crystallinity of the active layer and the cladding layer grown directly on the second nitride semiconductor layer is undoped. It tends to be slightly lower than when grown on the third nitride semiconductor layer.
Furthermore, by interposing an undoped third nitride semiconductor layer having a relatively high resistivity between the active layer and the second nitride semiconductor layer, leakage current of the element can be prevented and the reverse direction can be prevented. The breakdown voltage can be increased.
The thickness of the third nitride semiconductor layer is not particularly limited. Specifically, the thickness is not less than 10 angstroms and not more than 0.5 μm, preferably not less than 50 angstroms and not more than 0.2 μm, more preferably not less than 100 angstroms and not more than 0.15 μm. Adjust to. Since the third nitride semiconductor layer is an undoped layer and has a resistivity as high as 0.1 Ω · cm or more, when the third nitride semiconductor layer is grown to a thickness greater than 0.5 μm, the second nitride semiconductor layer Even if the resistivity of the nitride semiconductor layer is adjusted to be low, Vf tends to hardly decrease. A film thickness of 10 angstroms or more is preferable because the third nitride semiconductor layer can be easily formed.
[0024]
In the nitride semiconductor light emitting device of the present invention, the resistivity of the first and second nitride semiconductor layers formed between the substrate and the active layer, and the case where the third nitride semiconductor layer is formed. Shows the layer structure using the relationship between the resistivity of each of the first to third nitride semiconductor layers. From the substrate side, the first nitride semiconductor layer having a higher resistivity and carbon or carbon and n A second nitride semiconductor layer doped with a type impurity and having a resistivity lower than that of the first nitride semiconductor layer, and a third nitride semiconductor layer having a resistivity higher than that of the second nitride semiconductor layer And an n-electrode is formed on the second nitride semiconductor layer. The resistivity of the first to third nitride semiconductor layers is as described above.
[0025]
In the present invention, the layers other than the first to third nitride semiconductor layers constituting the element structure are not particularly limited, and any layer structure, element shape, electrode, and the like may be used.
For example, the active layer preferred in the present invention is desirably an undoped nitride semiconductor containing In, preferably a single quantum well structure having a well layer made of InGaN, or a multiple quantum well structure.
[0026]
【Example】
[Example 1]
FIG. 1 is a schematic cross-sectional view showing the structure of an LED device according to an embodiment of the present invention. The method for manufacturing the device of the present invention will be described below based on this drawing.
[0027]
The substrate 1 made of sapphire (C surface) is set in a reaction vessel, and after the inside of the vessel is sufficiently replaced with hydrogen, the temperature of the substrate is raised to 1050 ° C. while flowing hydrogen, and the substrate is cleaned. In addition to the sapphire C surface, the substrate 1 has sapphire whose main surface is the R surface and the A surface, and other spinels (MgA12OFourIn addition to an insulating substrate such as SiC), a semiconductor substrate such as SiC (including 6H, 4H, and 3C), Si, ZnO, GaAs, and GaN can be used.
[0028]
(Buffer layer 2)
Subsequently, the temperature is lowered to 510 ° C., hydrogen is used as a carrier gas, ammonia and TMG (trimethyl gallium) are used as a source gas, and a buffer layer 2 made of GaN is grown on the substrate 1 to a thickness of about 200 Å.
[0029]
(First nitride semiconductor layer 3)
After growing the buffer layer 2, only TMG is stopped and the temperature is raised to 1050 ° C. When the temperature reaches 1050 ° C., the first nitride semiconductor layer 3 made of undoped GaN is grown to a thickness of 1.5 μm, using TMG and ammonia gas as source gases.
[0030]
(Second nitride semiconductor layer 4)
Subsequently, at 1050 ° C., similarly, TMG, ammonia gas, silane gas as impurity gas, and dimethylamine are used as Si and 4 × 10 6 Si.18/ CmThreeA second nitride semiconductor layer 3 made of GaN containing doped carbon is grown to a thickness of 3 μm.
When another sapphire substrate not having an element structure is used and a wafer grown to the second nitride semiconductor layer in the same manner is prepared, and the resistivity of the second nitride semiconductor layer is measured, 5 × 10 5 is obtained.-3It was Ω · cm. Further, when the carbon concentration of the second nitride semiconductor layer is measured using a secondary ion mass spectrometer (SIMS), 3 × 1017/ CmThreeIt was doped with carbon at a considerable concentration. Moreover, in order to evaluate crystallinity, when the half value width (FWHM) of the rocking curve was measured using the X-ray-diffraction apparatus, it was 4 min and crystallinity was favorable.
Similarly to the second nitride semiconductor layer, when the carbon concentration of the first nitride semiconductor layer is measured, 7 × 1016/ CmThreeSince this value is almost the same as the background value, the first nitride semiconductor layer was hardly doped with carbon.
[0031]
(Third nitride semiconductor layer 5)
Next, after forming the second nitride semiconductor layer, silane gas and dimethylamine are stopped, and a third nitride semiconductor layer 5 made of undoped GaN is grown to a thickness of 0.15 μm at 1050 ° C. in the same manner.
[0032]
(Active layer 6)
Next, the temperature is set to 800 ° C., the carrier gas is switched to nitrogen, and undoped In using TMG, TMI (trimethylindium), and ammonia.0.25Ga0.75The active layer 6 having a single quantum well structure is grown by growing the N layer with a thickness of 30 angstroms.
[0033]
(P-side cladding layer 7)
Next, the temperature is increased to 1050 ° C., and TMG, TMA, ammonia, Cp2Mg (cyclopentadienylmagnesium) is used and Mg is 1 × 1020/cmThreeDoped p-type Al0.1Ga0.9A p-side cladding layer 7 made of N is grown to a thickness of 0.1 μm. This layer acts as a carrier confinement layer and is a nitride semiconductor containing Al, preferably AlYGa1-YIt is desirable to grow N (0 <Y <1). In order to grow a layer having good crystallinity, an Al value with a Y value of 0.3 or lessYGa1-YIt is desirable to grow the N layer with a film thickness of 0.5 μm or less.
[0034]
(P-side contact layer 8)
Subsequently, at 1050 ° C., TMG, ammonia, Cp2Mg is used, and Mg is 1 × 1020/cmThreeA p-side contact layer 8 made of doped p-type GaN is grown to a thickness of 0.1 μm. The p-side contact layer 8 is also InXAlYGa1-XYN (0.ltoreq.X, 0.ltoreq.Y, X + Y.ltoreq.1), and the composition thereof is not particularly limited. However, when GaN is used, a nitride semiconductor layer with few crystal defects can be easily obtained. And preferable ohmic contact is easily obtained.
[0035]
After the reaction is completed, the temperature is lowered to room temperature, and the wafer is annealed in a reaction vessel at 700 ° C. in a nitrogen atmosphere to further reduce the resistance of the p-type layer.
[0036]
After annealing, the wafer is taken out of the reaction vessel, a mask having a predetermined shape is formed on the surface of the uppermost p-side contact layer 8, and etching is performed from the p-side contact layer side with an RIE (reactive ion etching) apparatus. As shown in FIG. 1, the surface of the second nitride semiconductor layer 4 is exposed.
[0037]
After the etching, a translucent p-electrode 9 containing Ni and Au having a thickness of 200 angstroms is formed almost on the entire surface of the p-side contact layer on the uppermost layer, and a p-pad electrode made of Au for bonding on the p-electrode 9 10 is formed with a film thickness of 0.5 μm. On the other hand, an n-electrode 11 containing W and Al is formed on the surface of the second nitride semiconductor layer 4 exposed by etching. Finally, to protect the surface of the p-electrode 9, SiO2After the insulating film 12 is formed as shown in FIG. 1, the wafer is separated by scribe to form a 350 μm square LED element.
[0038]
This LED element emits blue light of 470 nm at a forward voltage of 20 mA, a buffer layer made of GaN on an sapphire substrate, an n-side contact layer made of Si-doped GaN, and an active layer made of InGaN having a single quantum well structure Compared with a conventional blue light emitting LED in which a p-side cladding layer made of Mg-doped AlGaN and a p-side contact layer made of Mg-doped GaN are sequentially laminated, Vf at 20 mA is 0.1 to 0.2 V, The output was improved by 5% to 10%.
[0039]
[Example 2]
In Example 1, an LED element is manufactured in the same manner except that the active layer is formed without forming the third nitride semiconductor layer. Although the obtained LED was slightly inferior in performance as compared with Example, it was almost as good as Example 1.
[0040]
【The invention's effect】
  The present invention8 × 10 carbon 16 / Cm 3 InAfter growing the undoped first nitride semiconductor layer,2x10 carbon 17 / Cm 3 More than,When the second nitride semiconductor layer doped with carbon or carbon and n-type impurities is grown, it can be grown as a thick layer with good crystallinity and low resistivity. When an n-electrode is formed on the second nitride semiconductor layer having a low rate, a nitride semiconductor light-emitting element capable of improving light emission efficiency and output, and reducing Vf and threshold value can be provided.
  Furthermore, when an undoped third nitride semiconductor is grown on the second nitride semiconductor layer, an underlying layer having good crystallinity for the nitride semiconductor layer grown on the third nitride semiconductor layer Thus, the resistivity of the second nitride semiconductor layer can be further reduced and the carrier concentration is increased, so that a very efficient nitride semiconductor light emitting device can be realized.
  As described above, according to the present invention, since a light emitting element having a low Vf and threshold value can be realized, an element having a reduced heat generation amount and improved reliability can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing the structure of an LED element according to an embodiment of the present invention.
[Explanation of symbols]
1 ... Board
2 ... Buffer layer
3... First nitride semiconductor layer
4 ... Second nitride semiconductor layer
5 ... Third nitride semiconductor layer
6 ... Active layer
7 ... p-side cladding layer
8 ... p-side contact layer
9 ... p electrode
10 ... P pad electrode
11 ... n electrode

Claims (4)

  1. Between the substrate and the active layer, at least an undoped first nitride semiconductor layer and an n-conductivity-type second nitride semiconductor layer containing carbon and Si as an n-type impurity are provided in order from the substrate side. The carbon concentration of the first nitride semiconductor layer is 7 × 10 16 / cm 3 or less, and the carbon concentration of the second nitride semiconductor layer is 2 × 10 17 / cm 3 to 1 × 10 20. / cm 3 der is, Ri further Na and n electrode is formed on the second nitride semiconductor layer, between the active layer and the second nitride semiconductor layer, a third nitride undoped nitride semiconductor light emitting device characterized Rukoto such to form a semiconductor layer.
  2. 2. The nitride semiconductor light-emitting element according to claim 1 , wherein the resistivity of the second nitride semiconductor layer is 1 × 10 −5 Ω · cm or more and less than 8 × 10 −3 Ω · cm.
  3. Between the substrate and the n conductivity type nitride semiconductor layer, nitride according to claim 1 or 2, characterized in that a buffer layer grown at a lower temperature than the n conductivity type nitride semiconductor layer Semiconductor light emitting device.
  4. The third film thickness of the nitride semiconductor layer, a nitride semiconductor light-emitting device according to any one of claims 1 to 3, wherein the at 0.5μm or less.
JP11654698A 1998-04-27 1998-04-27 Nitride semiconductor light emitting device Expired - Fee Related JP3897448B2 (en)

Priority Applications (1)

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Application Number Priority Date Filing Date Title
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JP3897448B2 true JP3897448B2 (en) 2007-03-22

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Publication number Priority date Publication date Assignee Title
JP3870807B2 (en) * 2001-12-20 2007-01-24 ソニー株式会社 Image display device and manufacturing method thereof
JP2009123718A (en) * 2007-01-16 2009-06-04 Showa Denko Kk Group iii nitride compound semiconductor element and its manufacturing method, group iii nitride compound semiconductor light-emitting element and its manufacturing method, and lamp
KR101175183B1 (en) * 2011-08-08 2012-08-17 일진머티리얼즈 주식회사 Nitride based light emitting diode with excellent current spreading effect and manufacturing method thereof
CN103094442A (en) * 2013-01-31 2013-05-08 马鞍山圆融光电科技有限公司 Nitride light emitting diode (LED) and preparation method thereof

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