JP2006108535A - Nitride compound semiconductor and method for manufacturing the same and its purpose of use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride compound semiconductor for applying an element showing high electrostatic breakdown resistance. <P>SOLUTION: (1) This nitride compound semiconductor is provided with a p-type contact layer and a light emission layer and an n-type contact layer, and characterized by laminating an n-type first layer expressed by a general formula In<SB>a</SB>Ga<SB>b</SB>Al<SB>c</SB>N(a+b+c=1, 0≤a≤1, 0≤b≤1, 0≤c≤1), and an n-type second layer expressed by In<SB>d</SB>Ga<SB>e</SB>Al<SB>f</SB>N(0≤d≤1, 0≤e≤1, 0≤f≤1, d+e+f=1), whose space charge density is lower than that of the first layer between the light emission layer and the p-type contact layer successively from the light emission layer side. (2) This nitride compound semiconductor is characterized so that the second layer can be constituted as an n-type impurity dope layer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

The present invention relates to a compound semiconductor represented by the general formula In _x Ga _y Al _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1), a manufacturing method thereof, and It relates to the use.

As a material of a light emitting element such as an ultraviolet or blue light emitting diode or a laser diode, the general formula In _x Ga _y Al _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1) ) Is known (hereinafter abbreviated as nitride compound semiconductor).
A light-emitting element made of such a nitride compound semiconductor has a voltage of 50 V or less (50 V or less) that is much weaker than static electricity generated in the human body in the process of manufacturing a light-emitting device incorporating the light-emitting element or operating the light-emitting device. Even in the case of electrostatic withstand voltage, the characteristics deteriorate, and in some cases, the element may be destroyed.

For example, a p-type cladding layer, a p-type lightly doped layer containing a p-type impurity at a lower concentration than the p-type cladding layer, and a p-type impurity at a higher concentration than the p-type cladding layer on the active layer. A nitride-based compound semiconductor device having a p-type contact layer is proposed, and this p-type lightly doped layer is grown at 1050 ° C. as undoped during growth. It is also disclosed that a p-type impurity doped in the p-type cladding layer is formed by diffusion during growth (for example, Patent Document 1).
In addition, a nitride-based compound semiconductor device in which an n-type multilayer film, a multiple quantum well, and a p-type multilayer film are stacked (for example, Patent Document 2), and more than an n-type contact layer between a light-emitting layer and an n-type contact layer. A nitride-based compound semiconductor device (for example, Patent Document 3) in which an n-type layer having a low electron concentration is provided at 1150 ° C. has been proposed.

JP 2001-148507 A Japanese Patent Laid-Open No. 2000-244072 JP-A-9-92880

  However, a nitride compound semiconductor device having a p-type cladding layer, a p-type lightly doped layer, and a p-type contact layer in this order on the active layer as described above, an n-type multilayer film, a multiple quantum well, and p Nitride-based compound semiconductor elements, etc., in which a multi-layered multilayer film is laminated cannot sufficiently satisfy electrostatic breakdown resistance, and a nitride-based compound semiconductor element in which an n-type layer having a low electron concentration is provided at 1150 ° C. Even if the electrostatic withstand voltage in the positive direction can be improved, there has been a problem that the improvement in the electrostatic withstand voltage in the reverse direction is insufficient.

  An object of the present invention is to solve the above-mentioned problems in the prior art, and to provide a nitride-based compound semiconductor that provides an element exhibiting high electrostatic breakdown resistance, a method for manufacturing the same, and a use thereof.

  As a result of intensive studies on the layer structure of a nitride-based compound semiconductor in order to solve the above-described problems, the present inventors have found that an n-type first layer is disposed between the light-emitting layer and the p-type contact layer in order from the light-emitting layer side. And a nitride-based compound semiconductor having a specific layer structure in which the n-type second layer having a lower space charge density than the first layer has a significantly improved electrostatic breakdown voltage The present invention has been completed by finding that a compound semiconductor device is provided, and by further various studies.

That is, the present invention provides [1] a nitride-based compound semiconductor including a p-type contact layer, a light-emitting layer, and an n-type contact layer, and in order from the light-emitting layer side between the light-emitting layer and the p-type contact layer, An n-type first layer represented by the general formula In _a Ga _b Al _c N (where a + b + c = 1, 0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1); N d type second represented by In _d Ga _e Al _f N (where 0 ≦ d ≦ 1, 0 ≦ e ≦ 1, 0 ≦ f ≦ 1, d + e + f = 1) having a lower space charge density than the layer of The present invention provides a nitride-based compound semiconductor comprising a layer.
The present invention also provides [2] a nitride compound semiconductor according to [1] above, wherein the second layer is an n-type impurity doped layer.

Furthermore, in manufacturing a nitride compound semiconductor having [3] a p-type contact layer, a light-emitting layer, and an n-type contact layer, the present invention is arranged in order from the light-emitting layer side between the light-emitting layer and the p-type contact layer. An n-type first layer represented by the general formula In _a Ga _b Al _c N (where a + b + c = 1, 0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1), N d type second represented by In _d Ga _e Al _f N (where 0 ≦ d ≦ 1, 0 ≦ e ≦ 1, 0 ≦ f ≦ 1, d + e + f = 1) having a lower space charge density than the first layer. A method of manufacturing a nitride-based compound semiconductor, characterized by growing a layer of
[4] The method for producing a nitride compound semiconductor according to [3], wherein the second layer is grown as an n-type impurity doped layer,
[5] A light emitting device using the nitride compound semiconductor according to [1] or [2] or the nitride compound semiconductor obtained by the production method according to [3] or [4],
Is to provide.

  The nitride-based compound semiconductor of the present invention is industrially advantageous because it provides a light emitting device exhibiting high electrostatic breakdown resistance.

Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.
The nitride-based compound semiconductor that is the subject of the present invention is represented by the general formula In _x Ga _y Al _z N (where x + y + z = 1, 0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ z ≦ 1). Compound semiconductor.

As a substrate for growing the nitride compound semiconductor, for example, a sapphire substrate, a SiC substrate, a Si substrate, a GaN substrate having a dislocation density reduced by embedded growth, a GaN substrate on Si, a free-standing GaN substrate, an AlN substrate, Examples include ZrB ₂ and CrB ₂ substrates.
Here, when the nitride compound semiconductor is grown directly on these substrates other than the nitride compound semiconductor substrate, a sufficiently high quality crystal may not be obtained due to lattice mismatch. In such a case, as a buffer layer, a layer of GaN, AlGaN, AlN, InGaAlN, SiC, or the like is first grown on the substrate at a low temperature of, for example, about 400 to 600 ° C., and then the nitride compound semiconductor is further grown. High-quality crystals can be obtained by the two-stage growth method.

FIG. 1 is a cross-sectional view schematically showing the structure of a light emitting device using the nitride-based compound semiconductor of the present invention.
As a method for producing the nitride-based compound semiconductor, various known methods can be mentioned, but it is preferable to use a metal organic chemical vapor deposition method (MOVPE method). Hereinafter, an example of the manufacturing method by the MOVPE method will be described.
A GaN buffer layer 2 is formed on the sapphire substrate 1, and an n-type contact layer 3 is further formed on the GaN buffer layer. The thickness of the GaN buffer layer 2 is preferably 10 to 100 nm. The substrate and buffer layer described above can also be used.

The n-type contact layer 3 preferably has a space charge density of 1 × 10 ¹⁸ cm ⁻³ or more and 1 × 10 ²¹ cm ⁻³ or less in order not to increase the operating voltage of the light emitting element. This space charge density corresponds to the ionized impurity concentration in the layer and corresponds to the thermally activated carrier concentration. Generally, it is a value obtained by a capacitance-voltage (CV) measurement method. Such an n-type contact layer is made of In _a Ga _b Al _c N at _a growth temperature of 900 ° C. to 1200 ° C. (where a + b + c = 1, 0 ≦ a <1, 0 <b ≦ 1, 0 ≦ c <1). It can be easily obtained by a known method in which an appropriate amount of n-type dopant gas or organic metal raw material is mixed during crystal growth. As the n-type dopant material, silane, disilane, germane, tetramethylgermanium, tetraethylgermanium and the like are suitable. Further, when the space charge density exceeds 1 × 10 ²¹ cm ⁻³ , the crystallinity tends to be deteriorated, which may adversely affect the characteristics of the light emitting device, which is not preferable.
In addition, when the mixed crystal ratio of In and Al is high, the crystal quality is deteriorated particularly at a low temperature and the space charge density is increased. Therefore, the In composition is preferably 5% or less, more preferably 1% or less. The Al composition is preferably 5% or less, more preferably 1% or less. The n-type contact layer 3 is most preferably GaN.

Next, a nitride represented by In _d Ga _e Al _f N (where d + e + f = 1, 0 ≦ d ≦ 1, 0 ≦ e ≦ 1, 0 ≦ f ≦ 1) is formed on the n-type contact layer 3. A system compound semiconductor layer 4 is provided.
The semiconductor layer 4 is preferably non-doped, and thereby, better electrostatic withstand voltage characteristics, better LED light emission characteristics, and electrical characteristics can be obtained. The growth temperature is usually in the range of 900 to 1200 ° C, preferably in the range of 1000 to 1150 ° C. For example, crystal growth is performed using a growth temperature of 1100 ° C., ammonia gas as a Group 5 material, and triethylgallium as a Group 3 material. At this time, the n-type dopant gas and the p-type dopant gas are not intentionally mixed and are set to non-doping conditions. The space charge density of the semiconductor layer 4 formed under such crystal growth conditions can be less than n-type 5 × 10 ¹⁶ cm ⁻³ . It is preferably 1 × 10 ¹⁶ cm ⁻³ or less.
However, if such a low carrier concentration layer is too thick, it becomes a series resistance component of the light emitting element, and therefore the thickness of the semiconductor layer 4 is preferably 600 nm or less. More preferably, it is 10-300 nm. More preferably, it is 50-300 nm.
The nitride-based compound semiconductor 4 has a high In / Al mixed crystal ratio, so that the crystal quality is lowered and the carrier concentration is increased particularly at low temperatures. Therefore, the In composition is preferably 5% or less, more preferably 1% or less. is there. The Al composition is preferably 5% or less, more preferably 1% or less. Most preferred is GaN.

Between the light emitting layer 5 and the nitride compound semiconductor layer 4, the general formula In _a Ga _b Al _c N (provided that, a + b + c = 1,0 ≦ a ≦ 1,0 ≦ b ≦ 1,0 ≦ c ≦ 1 A non-doped nitride compound semiconductor layer 4 ′ (not shown) may be provided. The semiconductor layer 4 ′ is usually grown in the range of 550 to 850 ° C., preferably in the range of 700 to 800 ° C. For example, the growth temperature is set to 775 ° C., ammonia gas is used as a Group 5 raw material, and triethylgallium is used as a Group 3 raw material for crystal growth. At this time, it is important that the n-type dopant gas and the p-type dopant gas are not mixed intentionally and the non-doping condition is used. The space charge density of the semiconductor layer 4 ′ formed under such crystal growth conditions can be n-type and 1 × 10 ¹⁷ to 1 × 10 ¹⁸ cm ⁻³ .
In the semiconductor layer 4 ′, when the mixed crystal ratio of In and Al is high, the crystal quality is deteriorated particularly at a low temperature and the carrier concentration is high. Therefore, the In composition is preferably 5% or less, more preferably 1% or less. . The Al composition is preferably 5% or less, more preferably 1% or less. Most preferred is GaN.

In addition, the electrostatic withstand voltage can be further improved by adjusting the film thickness of the semiconductor layer 4 ′. However, if the thickness of the semiconductor layer 4 ′ is too thin, the effect of improving the electrostatic withstand voltage tends to decrease, and if it is too thick, the element characteristics such as a tendency to increase the leakage current when the light emitting element operates are adversely affected. There is a risk of impact. Therefore, the film thickness of the semiconductor layer 4 ′ is usually in the range of 70 to 500 nm, preferably in the range of 70 to 250 nm.
The semiconductor layer 4 ′ may also serve as a barrier layer in contact with the light emitting layer under the well layer, or may be provided between the n-type contact layer 3 and the nitride compound semiconductor layer 4. It may also serve as a barrier layer in contact with the well layer, or may be provided between a first layer and a second layer, which will be described later, or between the second layer and the p-type contact layer 8. .

Next, the light emitting layer 5 is usually formed on the nitride semiconductor layer 4. The light emitting layer 5 shown in FIG. 1 includes a GaN layer 5A to 5F as a barrier layer, and an In _g Ga _h N (where g + h = 1, 0 <g <1, 0 <h <1) layer as a well layer. The multiple quantum well structure consisting of 5G to 5K. Although five well layers are shown in FIG. 1, at least one well layer is sufficient. Here, the film thicknesses and mixed crystal ratios of the GaN layers 5A to 5F and the In _g Ga _h N layer of 5G to 5K can be appropriately determined according to the characteristics of the target light emitting element. For example, if a blue light emitting device having an emission wavelength of about 470 nm is intended, the GaN layer may be 3 to 30 nm, the In _g Ga _h N layer may be 1 to 5 nm, and the average In composition may be about 5 to 40%.
Moreover, the growth temperature of a barrier layer is 500-1000 degreeC normally, Preferably it is 700-900 degreeC, and the growth temperature of a well layer is 650-850 degreeC normally, Preferably it is 700-850 degreeC.

In the present invention, a general formula In _a Ga _b Al _c N (where a + b + c = 1, 0 ≦ a ≦ 1, 0 ≦ b ≦) is provided between the light emitting layer 5 and the p-type contact layer 8 described later. An n-type first layer represented by 1, 0 ≦ c ≦ 1) and In _d Ga _e Al _f N having a lower space charge density than the first layer (where 0 ≦ d ≦ 1, 0 ≦ e ≦ 1, 0 ≦ f ≦ 1, d + e + f = 1) and an n-type second layer.
Here, from the viewpoint of improving the light emission characteristics by making the carrier confinement effective, the first layer 6 is preferably AlGaN so that the potential barrier in the conduction band can be increased with respect to the light emitting layer. Further, the growth temperature of the first layer 6 is desirably a relatively low temperature comparable to the growth temperature of the light emitting layer because the heat resistance of the light emitting layer is low. However, growing at a low temperature causes many crystal defects, and therefore, it tends to be an n-type having a high space charge density. Therefore, it is necessary to supply a p-type dopant in order to obtain an n-type having a relatively low space charge density. is there. Further, when a p-type dopant is used, this may diffuse from the first layer to the light emitting layer during the growth of the second layer 7 and the p-type contact layer 8, which will be described later, and adversely affect the light emission characteristics. Therefore, as the p-type dopant, Mg (Japanese Patent Laid-Open No. 2002-158375) that can obtain an n-type having a relatively low concentration and a low space charge density is preferably used. The space charge density in the first layer 6 is usually 1 × 10 ^{14 to} 5 × 10 ¹⁸ cm ⁻³ , preferably 1 × 10 ¹⁵ to 1 × 10 ¹⁸ cm ⁻³ .

  When the well layer is exposed to a temperature higher than its growth temperature, the crystal quality may be deteriorated, such as phase separation or destruction of the crystal structure. In order to prevent such deterioration of the well layer due to heat, the first layer 6 is preferably grown at a low temperature, usually 700 to 1100 ° C., preferably 750 to 1000 ° C., more preferably 750 to 900 ° C. Grow in. Regarding the film thickness, a thin film is preferable for good charge injection, but it is preferable to keep a distance from the p-type contact layer grown at a high temperature in order to prevent the well layer from being thermally deteriorated. The 1st layer 6 is 0.5 nm-3000 nm normally, Preferably it is 0.5 nm-100 nm, More preferably, it is 0.5 nm-50 nm.

Further, when the second layer 7 is a mixed crystal such as AlInGaN, it is not easy to control the space charge density because the band gap changes depending on the mixed crystal ratio and the crystal quality changes. Tend to be. Therefore, the second layer 7 is preferably GaN. In the second layer 7, the space charge density needs to be lower than the space charge density of the n-type first layer 6 and is usually 10 ¹⁷ cm ⁻³ or less, preferably 10 ¹⁶ cm ⁻³ or less. is there.
Here, if the space charge density in the second layer is too high, not only the effect of improving the electrostatic withstand voltage tends to be reduced but also the efficiency of hole injection into the light emitting layer tends to be lowered, which is not preferable. In addition, by making the second layer 7 n-type, the depletion layer near the pn junction interface can be easily spread, and the electrostatic withstand voltage can be further improved.

Here, as a method of growing the second layer 7 having a low space charge density, when the same growth apparatus as the first layer 6 using the p-type dopant raw material is used, due to the memory effect of the p-type dopant source, Since the p-type dopant is mixed in the second layer 7, it is not easy to control the space charge density of the second layer. Therefore, in this case, an n-type dopant is doped. This makes it possible to easily control the space charge density with good reproducibility.
On the other hand, in the case of using a growth apparatus that does not have the risk of developing the memory effect of the p-type dopant source, such as a growth apparatus that does not use the p-type dopant source, or a growth apparatus that has been sufficiently cleaned after using the p-type dopant source. The space charge density can be reduced without doping with an n-type dopant, and can be made lower than the space charge density of the first layer.

  When doping an n-type dopant, a group 4 element and a group 6 element are usually used. Specific examples include Si, Ge, and O, and Si is preferable because it is easy to form an n-type and can be obtained with high raw material purity. Silane, disilane, and the like are suitable as the Si dopant material. As a raw material for the Ge dopant, germane, tetramethylgermanium, tetraethylgermanium and the like are suitable.

The film thickness of the second layer 7 is usually 20 nm to 2000 nm, preferably 100 nm to 2000 nm, more preferably 200 nm to 2000 nm. Here, if the thickness of the second layer 7 is too thin, it is difficult to obtain the effect of high electrostatic withstand voltage, and if it is too thick, current tends to hardly flow through the light emitting element, and the luminous efficiency of the element tends to decrease. The driving voltage tends to increase.
The growth temperature of the second layer 7 is preferably higher because the reproducibility of the space charge density is improved when the crystal quality is increased. However, if the growth temperature is increased, the p-type dopant of the first layer 6 described above may diffuse into the light emitting layer, which may adversely affect the quality of the light emitting layer. Absent. The second growth temperature is usually grown in the range of 800 to 1200 ° C. Preferably, it grows in the range of 900-1150 degreeC.

Next, the p-type contact layer 8 is formed on the second layer 7. The p-type contact layer 8 is preferably p-type having a space charge density of 5 × 10 ¹⁵ cm ⁻³ or more so as not to increase the operating voltage of the light emitting element. More preferably, it is 1 * 10 < ¹⁶ > -5 * 10 < ¹⁹ > cm < ^-3 >. Such a p-type contact layer is made of In _a Ga _b Al _c N at _a growth temperature of 800 ° C. to 1100 ° C. (where a + b + c = 1, 0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1). It can be easily obtained by a known method such as heat treatment after crystal growth by mixing an appropriate amount of dopant source gas during crystal growth.
Since the p-type contact layer 8 tends to have high contact resistance when the mixed crystal ratio of Al is high, the Al composition is usually 5% or less, preferably 1% or less. More preferred is InGaN, GaN, and most preferred is GaN.

The p-type contact layer 8 may be a multilayer film. In this case, a stacked structure of In _a Ga _b Al _c N (a + b + c = 1, 0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1) having different compositions can be used. In order to reduce the contact resistance with the electrode, the layer in contact with the electrode should have a higher space charge density, and is preferably InGaN or GaN.

Here, if the thickness of the p-type layer is too thin, good contact resistance cannot be obtained. Preferably, it is 300 nm, more preferably 400 nm, still more preferably 500 nm or more, and most preferably 600 nm or more. By increasing the thickness of the p-type layer, the electrostatic withstand voltage is further improved. When the film thickness is 500 nm or more, the light output is further improved. Therefore, by providing the total film thickness of the p-type layer to 500 nm or more, it is possible to provide a light-emitting element that has more excellent light output and electrostatic withstand voltage. Can do.
On the other hand, if the p-layer film thickness is too large, problems such as warping of the substrate and an increase in manufacturing time occur. Preferably it is 3 micrometers or less.

  When each layer as described above is grown using the MOVPE method, it can be appropriately selected from the following raw materials and used.

Examples of Group 3 gallium raw materials include general formulas R ₁ R ₂ R ₃ Ga such as trimethyl gallium (TMG) and triethyl gallium (TEG) (where R ₁ , R ₂ and R ₃ represent lower alkyl groups). And trialkylgallium.

As an aluminum raw material, general formula R ₁ R ₂ R ₃ Al such as trimethylaluminum (TMA), triethylaluminum (TEA), triisobutylaluminum (wherein R ₁ , R ₂ and R ₃ represent lower alkyl groups). ) Represented by trialkylaluminum.

As an indium raw material, a trialkyl represented by a general formula R ₁ R ₂ R ₃ In (wherein R ₁ , R ₂ and R ₃ represent lower alkyl groups) such as trimethylindium (TMI) and triethylindium. Examples thereof include those obtained by exchanging 1 to 3 alkyl groups with halogen atoms from trialkylindium such as indium and diethylindium chloride, and indium halides represented by the general formula InX (X is a halogen atom) such as indium chloride.

  Examples of the Group 5 materials include ammonia, hydrazine, methyl hydrazine, 1,1-dimethylhydrazine, 1,2-dimethylhydrazine, t-butylamine, ethylenediamine, and the like. These can be used alone or in combination in any combination. Among these raw materials, ammonia and hydrazine are preferable because they do not contain carbon atoms in the molecule and are less affected by carbon contamination in the semiconductor.

Examples of the p-type dopant include Mg, Zn, Cd, Ca, and Be. Of these, Mg and Ca are preferably used. As a raw material of Mg which is a p-type dopant, for example, biscyclopentadiethyl magnesium [(C ₅ H ₅ ) ₂ Mg], bismethylcyclopentadiethyl magnesium [(C ₅ H ₄ CH ₃ ) ₂ Mg], bisethylcyclo Pentadiethyl magnesium [(C ₅ H ₄ C ₂ H ₅ ) ₂ Mg] and the like can be used. As a raw material of Ca, biscyclopentadienyl calcium ((C ₅ H ₅ ) ₂ Ca) and its derivatives, for example, bismethylcyclopentadienyl calcium ((C ₅ H ₄ CH ₃ ) ₂ Ca), bisethyl Cyclopentadienyl calcium ((C ₅ H ₄ C ₂ H ₅ ) ₂ Ca), bisperfluorocyclopentadienyl calcium ((C ₅ F ₅ ) ₂ Ca), or di-1-naphthalenyl calcium and Derivatives thereof, or calcium acetylide and derivatives thereof, such as bis (4,4-difloro-3-buten-1-ynyl) -calcium, bisphenylethynyl calcium and the like can be used. These raw materials may be used alone or in combination.

  In the present embodiment, the case where the MOVPE method is used has been described. However, the present invention is not limited to this method, and other known nitride-based compound semiconductor crystal growth methods such as molecular beam epitaxy may be used. it can.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail based on an Example, this invention is not limited to these.

Example 1
Film formation by crystal growth using the MOVPE method was performed, and a light-emitting element having the layer structure of FIG. 1 was formed on a sapphire (0001) substrate. The detailed procedure is as follows.
First, the pressure in the growth furnace is set to 1 atm, hydrogen is used as a carrier gas, ammonia, TMG, and silane are used as raw materials, and GaN as a low-temperature buffer layer is grown to about 50 nm at 485 ° C. Then, Si is added at 1040 ° C. About 4 μm of doped n-type GaN was grown. Next, 0.3 μm of undoped GaN was grown.

Next, the temperature is lowered to 730 ° C., the pressure in the growth furnace is set to 1/2 atmosphere, carrier gas is nitrogen, TEG, ammonia, and silane are supplied at 610 sccm, 40 slm, and 10 sccm, respectively, and Si as a barrier layer is doped. Then, after maintaining the GaN layer of 15 nm for 3 minutes without supplying the Group 3 raw material, 610 sccm, 1160 sccm, and 40 slm of TEG, TMI, and ammonia are supplied, respectively, and 3 nm of In as a well layer is supplied. _{A 0.12} Ga _0.88 N layer was grown and then held for 5 minutes without supplying the Group 3 material.
This operation of growing a 15 nm Si-doped GaN barrier layer and a 3 nm In _0.12 Ga _0.88 N well layer was repeated four more times, and only the uppermost barrier layer was made non-doped GaN with a thickness of 18 nm.

Next, the pressure in the growth furnace is 1 atm, nitrogen is supplied as a carrier gas at 32.5 slm, ammonia is 6.6 slm, TEG is 120 sccm, TMA is 7.2 sccm, Mg raw material is bisethylcyclopentadiene. The supply of 800 sccm of enilmagnesium was conducted, and an Al _0.05 Ga _0.95 N layer doped with Mg as a first layer was grown at 800 nm at 25 ° C.

  After the growth of the first layer, the temperature was raised to 1060 ° C., hydrogen was supplied at 25.7 slm, ammonia was 7.5 slm, TMG was 40 sccm, and Si was diluted to 4.67 ppm with nitrogen as the Si raw material to 14 sccm. The Si-doped GaN layer was grown to 1000 nm as the second layer.

  Thereafter, the temperature is lowered to 1040 ° C., hydrogen is supplied at 25.7 slm as a carrier gas, ammonia is supplied at 7.5 slm, TMG is supplied at 40 sccm, bisethylcyclopentadienylmagnesium is supplied at 980 sccm, and a Mg-doped GaN layer is formed at 150 nm. Grown up.

The nitride compound semiconductor manufactured as described above was heat-treated at 800 ° C. for 0.8 minutes in an atmosphere of ₃ sccm of NH ₃ , 75 sccm of O ₂ and 1500 sccm of N ₂ .

Next, a p-electrode pattern is formed on the surface by photolithography, stacked and deposited by vacuum evaporation in the order of NiAuPt, and an electrode pattern is formed by lift-off, followed by heat treatment at 380 ° C. in an O ₂ atmosphere to form an ohmic p-electrode. Was made. Next, an n electrode pattern was formed by photolithography, and etching was performed so that the n layer was exposed by dry etching. After removing the mask, an n-electrode pattern was formed on the dry-etched surface by photolithography, Al was deposited by vacuum deposition, and then an electrode pattern was formed by lift-off to form an n-electrode. The electrode area of the p electrode is 3.14 × 10 ⁻⁴ cm ² .
When voltage was applied to the light-emitting element thus obtained and the light-emitting characteristics were examined in the wafer state, it showed clear blue light emission at 20 mA in the forward direction.
In addition, the capacitance-voltage measurement method using an electrolytic solution and the evaluation by the photovoltaic method are performed. The Mg-doped GaN layer is a low-resistance p-type layer having a space charge density of about 1 × 10 ¹⁹ cm ^−3. I confirmed that there was.

The light emitting device was tested for resistance to electrostatic discharge as follows.
FIG. 2 is a circuit diagram for testing the resistance of the light emitting element to electrostatic discharge. Here, Vo is a variable DC power supply, Rp and R are resistors, C is a capacitor, and Sw is a changeover switch. The machine model test was conducted as follows. The machine model test is a model in which an electrostatic discharge is performed on an LED from an electrostatically charged device or jig, and the conditions are R = 0Ω and C = 200 pF. The voltage of the variable DC power supply Vo in FIG. 2 is set to a certain value, the changeover switch Sw is changed over as indicated by the solid line, and the capacitor C is charged via the resistor Rp, and then the changeover switch Sw is indicated by the dotted line. Then, the light emitting element is discharged. After repeating this three times, the voltage-current characteristics of the light emitting element were evaluated. It is determined whether or not the light emitting element has been destroyed by changing the voltage-current characteristics. Hereinafter, the Vo value when 50% of all the measured elements were destroyed was defined as the electrostatic withstand voltage value. The electrostatic withstand voltage of the light emitting element in this example was 140V.

In order to evaluate the conductivity of the first layer grown under the above conditions, the first layer was grown under the same growth conditions as above on the sample obtained by growing undoped GaN on the sapphire substrate. When the conductivity type and space charge density of this sample were evaluated by a capacitance-voltage measurement method using an electrolytic solution and a photovoltaic method, it was about 5 × 10 ¹⁷ cm ⁻³ for the n-type.
Similarly, in order to evaluate the conductivity of the second layer grown under the above conditions, a second layer was grown under the same growth conditions as above on a sample obtained by growing undoped GaN on a sapphire substrate. When the conductivity type and space charge density of this sample were evaluated by a capacitance-voltage measurement method using an electrolytic solution and a photovoltaic method, the conductivity and space charge density of the second layer were about 2 × in the n-type. 10 ¹⁷ cm ⁻³ .

(Example 2)
In the growth of the Si-doped GaN layer as the second layer, a light emitting device was produced and evaluated in the same manner as in Example 1 except that 10 sccm of silane was supplied. The light emission characteristics were as high as practical enough to withstand 20 mA, and the electrostatic withstand voltage was 275V. The space charge density of the second layer was about 3 × 10 ¹⁶ cm ⁻³ .

(Comparative Example 1)
A light emitting device was fabricated in the same manner as in Example 1 except that after the growth of the first layer, the Mg-doped AlGaN layer, the second layer was not grown, but the Mg-doped GaN layer was grown. ,evaluated. The light emission characteristic was 20 mA in the forward direction, showed clear blue light emission, and the electrostatic withstand voltage was 60V.

(Comparative Example 2)
In the growth of the second layer GaN layer, a light emitting device was produced and evaluated in the same manner as in Example 1 except that silane was not supplied (non-doped). The light emission characteristic was 20 mA in the forward direction, showed clear blue light emission, and the electrostatic withstand voltage was 40V. On the other hand, the conductivity and space charge density of the second layer were 4 × 10 ¹⁸ cm ⁻³ for the p-type.

Sectional drawing which shows an example of the light emitting element which consists of a nitride type compound semiconductor manufactured with the manufacturing method of this invention. The circuit diagram for testing the tolerance with respect to the electrostatic discharge of a light emitting element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Low-temperature buffer layer 3 N-type contact layer 4 Nitride-based compound semiconductor layer 5 Light emitting layer 5A to 5F Barrier layer 5G to 5K Well layer 6 First layer 7 Second layer 8 P-type contact layer 9 N electrode 10 p-electrode

Claims (5)

A nitride-based compound semiconductor including a p-type contact layer, a light-emitting layer, and an n-type contact layer, and having a general formula In _a Ga _b Al _{c in} order from the light-emitting layer side between the light-emitting layer and the p-type contact layer. An n-type first layer represented by N (where a + b + c = 1, 0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ c ≦ 1) and a lower space charge density than the first layer And an n-type second layer represented by In _d Ga _e Al _f N (where 0 ≦ d ≦ 1, 0 ≦ e ≦ 1, 0 ≦ f ≦ 1, d + e + f = 1) Nitride compound semiconductor.   The nitride-based compound semiconductor according to claim 1, wherein the second layer is an n-type impurity doped layer. In manufacturing a nitride-based compound semiconductor including a p-type contact layer, a light-emitting layer, and an n-type contact layer, the general formula In _a Ga _b Al is sequentially formed between the light-emitting layer and the p-type contact layer from the light-emitting layer side. _c n (provided that, a + b + c = 1,0 ≦ a ≦ 1,0 ≦ b ≦ 1,0 ≦ c ≦ 1) and the n-type first layer represented by the space charge density than the first layer Growing an n-type second layer represented by low In _d Ga _e Al _f N (where 0 ≦ d ≦ 1, 0 ≦ e ≦ 1, 0 ≦ f ≦ 1, d + e + f = 1). A method for producing a nitride-based compound semiconductor.   4. The method for producing a nitride-based compound semiconductor according to claim 3, wherein the second layer is grown as an n-type impurity doped layer.   A light emitting device comprising the nitride compound semiconductor according to claim 1 or 2 or the nitride compound semiconductor obtained by the production method according to claim 3 or 4.

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