JP5420515B2 - Nitride semiconductor light emitting device - Google Patents

Description

  The present invention relates to a nitride semiconductor light emitting device, and more particularly to a nitride semiconductor light emitting device having a tunnel junction.

  Conventionally, in a nitride semiconductor light emitting diode element in which the p-type nitride semiconductor layer side is the light extraction side, the p-side electrode formed on the p-type nitride semiconductor layer satisfies the following three conditions: Is required.

  First, the first condition is that the transmittance with respect to the light emitted from the nitride semiconductor light emitting diode element is high. Next, the second condition is to have a resistivity and a thickness capable of sufficiently diffusing the injected current in the plane of the light emitting layer. Finally, the third condition is that the contact resistance with the p-type nitride semiconductor layer is low.

  As the p-side electrode formed on the p-type nitride semiconductor layer of the nitride semiconductor light-emitting diode element in which the p-type nitride semiconductor layer side is the light extraction side, conventionally, about several to 10 nm of palladium, nickel, etc. A translucent metal electrode made of a thick metal film was formed on the entire surface of the p-type nitride semiconductor layer. However, such a translucent metal electrode has a low transmittance of about 50% with respect to the light emitted from the nitride semiconductor light-emitting diode element, so that the light extraction efficiency is lowered and a high-luminance nitride semiconductor light-emitting diode element is obtained. There was a problem that it was difficult.

  Therefore, the light extraction efficiency is improved by forming a transparent conductive film made of ITO (Indium Tin Oxide) over the entire surface of the p-type nitride semiconductor layer in place of the translucent metal electrode made of a metal film such as palladium or nickel. High brightness nitride semiconductor light emitting diode devices have been manufactured. The contact resistance between the transparent conductive film and the p-type nitride semiconductor layer, which has been a concern in the nitride semiconductor light-emitting diode element formed with such a transparent conductive film, is also improved by heat treatment or the like.

  Patent Document 1 discloses a group III nitride having at least a first n-type group III nitride semiconductor multilayer structure, a p-type group III nitride semiconductor multilayer structure, and a second n-type group III nitride semiconductor multilayer structure. An n-type group III nitride semiconductor layer in the first n-type group III nitride semiconductor multilayer structure is provided with a negative electrode, and a second n-type group III group is formed on the substrate. The n-type group III nitride semiconductor layer in the nitride semiconductor multilayer structure is provided with a positive electrode, and the n-type group III nitride semiconductor layer and the p-type III in the second n-type group III nitride semiconductor multilayer structure are provided. A nitride semiconductor light-emitting diode element in which a tunnel junction is formed by a p-type group III nitride semiconductor layer having a group nitride semiconductor multilayer structure is disclosed.

  In the nitride semiconductor light emitting diode element disclosed in Patent Document 1, the positive electrode is formed on the n-type group III nitride semiconductor layer in the second n-type group III nitride semiconductor multilayer structure, and the n-type Since the group III nitride semiconductor can easily increase the carrier concentration as compared with the p-type group III nitride semiconductor, compared with the conventional structure in which the positive electrode is formed on the p-type group III nitride semiconductor layer. The contact resistance can be reduced, the drive voltage is low, and a large output drive is possible. Further, it is said that reliability can be improved because heat generation at the positive electrode, which has been one of the causes of failure of the nitride semiconductor light emitting diode element, is reduced.

JP 2002-319703 A

  However, the transparent conductive film made of ITO has a problem that the optical properties are irreversibly changed at high temperatures, and the visible light transmittance is lowered. In addition, when a transparent conductive film made of ITO is used, the temperature range of the process after the formation of the transparent conductive film made of ITO is limited in order to prevent a reduction in visible light transmittance. There was a problem. Furthermore, the transparent conductive film made of ITO has a problem that it deteriorates due to driving at a high current density and becomes black.

  In the nitride semiconductor light-emitting diode element described in the example of Patent Document 1, a tunnel junction is formed by a p-type InGaN layer and an n-type InGaN layer having an In (indium) composition ratio comparable to that of the light-emitting layer. The thickness of each layer is 50 nm.

As described in the example of Patent Document 1, in order to sufficiently supply In as a solid phase, it is necessary to lower the growth temperature to about 800 ° C. However, since it is difficult to obtain a p-type InGaN layer having a high carrier concentration of 1 × 10 ¹⁹ / cm ³ or higher at low temperature, voltage loss at the tunnel junction cannot be reduced, resulting in a drive voltage of There was a problem of becoming higher.

  Accordingly, an object of the present invention is to provide a nitride semiconductor light emitting device capable of reducing the driving voltage.

The present invention relates to a substrate, a first n-type nitride semiconductor layer, a light emitting layer, a p-type nitride semiconductor layer, a p-type nitride semiconductor tunnel junction layer, and an n-type nitride formed on the substrate. An n-type nitride semiconductor tunnel junction layer, an n-type nitride semiconductor evaporation suppression layer, and a second n-type nitride semiconductor layer, wherein the p-type nitride semiconductor tunnel junction layer and the n-type nitride semiconductor tunnel junction layer are A tunnel junction is formed, the p-type nitride semiconductor tunnel junction layer is p-type InGaN, the n-type nitride semiconductor tunnel junction layer is n-type GaN, and one of the n-type nitride semiconductor tunnel junction layers The n-type nitride has a surface in contact with one surface of the p-type nitride semiconductor tunnel junction layer, and the other surface of the n-type nitride semiconductor tunnel junction layer has a larger band gap than the n-type nitride semiconductor tunnel junction layer In contact with the semiconductor evaporation suppression layer The shortest distance between the interface between the n-type nitride semiconductor tunnel junction layer and the n-type nitride semiconductor evaporation suppression layer and the interface between the p-type nitride semiconductor tunnel junction layer and the n-type nitride semiconductor tunnel junction layer is less than 40 nm. A nitride in which the thickness of the p-type nitride semiconductor tunnel junction layer is 4 nm or more and 6 nm or less, and the concentration of the n-type dopant in the n-type nitride semiconductor tunnel junction layer is less than 5 × 10 ¹⁹ / cm ³ It is a semiconductor light emitting device.

  In the nitride semiconductor light emitting device of the present invention, the n-type dopant is preferably at least one selected from the group consisting of Si, Ge and O.

In the nitride semiconductor light emitting device of the present invention, the p-type dopant concentration in the p-type nitride semiconductor tunnel junction layer is preferably 2 × 10 ¹⁹ / cm ³ or more.

The present invention also provides a substrate, a first n-type nitride semiconductor layer formed on the substrate, a light emitting layer, a p-type nitride semiconductor layer, a p-type nitride semiconductor tunnel junction layer, n A p-type nitride semiconductor tunnel junction layer and an n-type nitride semiconductor tunnel junction layer, comprising: a p-type nitride semiconductor tunnel junction layer; an n-type nitride semiconductor evaporation suppression layer; and a second n-type nitride semiconductor layer. The p-type nitride semiconductor tunnel junction layer is p-type InGaN, the n-type nitride semiconductor tunnel junction layer is n-type GaN, and the n-type nitride semiconductor tunnel junction layer One surface is in contact with one surface of the p-type nitride semiconductor tunnel junction layer, and the other surface of the n-type nitride semiconductor tunnel junction layer is n-type having a larger band gap than the n-type nitride semiconductor tunnel junction layer. In contact with the nitride semiconductor evaporation suppression layer And the other surface of the p-type nitride semiconductor tunnel junction layer is in contact with the p-type nitride semiconductor layer having a larger band gap than the p-type nitride semiconductor tunnel junction layer, and the n-type nitride semiconductor tunnel junction layer And the shortest distance between the interface between the n-type nitride semiconductor tunnel junction layer and the interface between the p-type nitride semiconductor tunnel junction layer and the n-type nitride semiconductor tunnel junction layer, and the p-type nitride semiconductor tunnel junction layer The shortest distance between at least one of the interface between the p-type nitride semiconductor layer and the interface between the p-type nitride semiconductor tunnel junction layer and the n-type nitride semiconductor tunnel junction layer is less than 40 nm, p-type the thickness of the nitride semiconductor tunnel junction layer has a 4nm than 6nm or less, the nitride semiconductor light emitting concentration of n-type dopant in the n-type nitride semiconductor tunnel junction layer is less than 5 × 10 ¹⁹ / cm ³ It is a child.

  In the nitride semiconductor light emitting device of the present invention, the n-type dopant is preferably at least one selected from the group consisting of Si, Ge and O.

In the nitride semiconductor light emitting device of the present invention, the p-type dopant concentration in the p-type nitride semiconductor tunnel junction layer is preferably 2 × 10 ¹⁹ / cm ³ or more.

  In the present invention, “p-type dopant concentration” indicates the atomic concentration of the p-type dopant contained in the nitride semiconductor, and “n-type dopant concentration” indicates the n-type dopant atom contained in the nitride semiconductor. The concentration is shown and can be quantitatively calculated by a method such as SIMS (Secondary Ion Mass Spectrometry).

  In this specification, Al represents aluminum, Ga represents gallium, and In represents indium.

  ADVANTAGE OF THE INVENTION According to this invention, the nitride semiconductor light-emitting device which can reduce a drive voltage can be provided.

It is typical sectional drawing of a preferable example of the nitride semiconductor light-emitting diode element which is an example of the nitride semiconductor light-emitting element of this invention. It is typical sectional drawing of another preferable example of the nitride semiconductor light-emitting diode element which is an example of the nitride semiconductor light-emitting element of this invention. FIG. 3 is a diagram showing the relationship between the thickness (nm) of the p-type tunnel junction layer and the drive voltage (V) of the nitride semiconductor light-emitting diode element of Example 1. FIG. 6 is a diagram showing the relationship between the thickness (nm) of the p-type tunnel junction layer and the drive voltage (V) of the nitride semiconductor light-emitting diode element of Example 3. It is typical sectional drawing of another preferable example of the nitride semiconductor light-emitting diode element which is an example of the nitride semiconductor light-emitting element of this invention.

  Embodiments of the present invention will be described below. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts.

  FIG. 1 shows a schematic cross-sectional view of a preferred example of a nitride semiconductor light-emitting diode element which is an example of the nitride semiconductor light-emitting element of the present invention. Here, the nitride semiconductor light-emitting diode element shown in FIG. 1 includes a substrate 1, a first n-type nitride semiconductor layer 2, a light-emitting layer 3, and a p-type nitride that are sequentially stacked on the substrate 1. A semiconductor layer 4, a p-type nitride semiconductor tunnel junction layer 5, an n-type nitride semiconductor tunnel junction layer 6, an n-type nitride semiconductor evaporation suppression layer 10, a second n-type nitride semiconductor layer 7, The n-side electrode 8 is formed on the first n-type nitride semiconductor layer 2 and the p-side electrode 9 is formed on the second n-type nitride semiconductor layer 7. ing.

  In the nitride semiconductor light emitting device having such a configuration, the contact resistance can be reduced and the driving voltage can be lowered as compared with the conventional structure in which the positive electrode is formed on the conventional p-type nitride semiconductor layer. On the other hand, there is a question as to how the voltage loss at the tunnel junction which is the junction between the p-type nitride semiconductor tunnel junction layer 5 and the n-type nitride semiconductor tunnel junction layer 6 can be reduced.

  The tunneling probability Tt at this tunnel junction is generally expressed by the following equation (1).

Tt = exp ((- 8π ( 2m e) 1/2 Eg 3/2) / (3qhε)) ... (1)
In the above formula (1), Tt denotes a tunneling probability, m _e denotes the effective mass of the conduction electrons, Eg represents an energy gap, q represents an electron charge, h represents the Planck's constant, ε represents an electric field applied to the tunnel junction.

  In order to reduce the driving voltage of the nitride semiconductor light emitting device, it is desired to increase the tunneling probability Tt. From the above equation (1), as a method for increasing the tunneling probability Tt, it is conceivable to increase the electric field ε applied to the tunnel junction.

  Here, as a method of increasing the electric field ε applied to the tunnel junction, effective ionized impurity concentrations of both the p-type nitride semiconductor tunnel junction layer 5 and the n-type nitride semiconductor tunnel junction layer 6 forming the tunnel junction are used. Is preferably increased. As a method for increasing the effective ionized impurity concentration, there is a method using a two-dimensional electron gas generated at an interface where layers having different band gaps are stacked.

  That is, a p-type nitride semiconductor tunnel that forms a tunnel junction is formed by positioning the generation site of the two-dimensional electron gas in the vicinity of the interface between the p-type nitride semiconductor tunnel junction layer 5 and the n-type nitride semiconductor tunnel junction layer 6. Since the effective ionized impurity concentration of the junction layer 5 and / or the n-type nitride semiconductor tunnel junction layer 6 can be increased, the electric field ε applied to the tunnel junction can be increased. Further, by increasing the electric field ε applied to the tunnel junction, a narrower depletion layer can be formed, so that the tunneling probability is improved.

  Therefore, as a result of intensive studies by the present inventor, the p-type nitride semiconductor tunnel junction layer 5 and / or the n-type nitride semiconductor tunnel junction layer 6 contain In, and the p-type nitride semiconductor tunnel junction At least one of the layers containing In which is at least one of the layer 5 and the n-type nitride semiconductor tunnel junction layer 6 is in contact with a layer having a larger band gap, and the layer containing In and the layer having a larger band gap At least one of the shortest distances between the interface and the interface between the p-type nitride semiconductor tunnel junction layer 5 and the n-type nitride semiconductor tunnel junction layer 6 is less than 40 nm, preferably 20 nm or less, more preferably 15 nm or less. Thus, even when the ionized impurity concentration of the p-type nitride semiconductor tunnel junction layer 5 is low, the nitride semiconductor including the tunnel junction It found that can reduce the driving voltage of the optical elements, and have completed the present invention.

  Here, from the viewpoint of reducing the drive voltage and reducing the amount of light absorbed from the light emitting layer 3, the above shortest distance is preferably as short as possible, but if it is too short, the layer containing In When the In content (ratio of the number of In atoms to the total number of Al, Ga, and In atoms in the In-containing layer) becomes small, the carrier concentration on the layer side with a large band gap is low in the In-containing layer. There is a possibility that the depletion layer reaches the part and the tunnel probability becomes small.

  Therefore, from the above viewpoint, the shortest distance is preferably greater than 2 nm. In this case, it is possible to reduce the decrease in the tunnel probability of the tunnel junction between the p-type nitride semiconductor tunnel junction layer 5 and the n-type nitride semiconductor tunnel junction layer 6.

  From the above viewpoint, the In content of the layer containing In (ratio of the number of In atoms to the total number of Al, Ga and In atoms in the In-containing layer) is preferably larger than 0.1. The upper limit may be 1.

  In the above, as the substrate 1, for example, a silicon substrate, a silicon carbide substrate, a zinc oxide substrate, or the like can be used.

  In the above, as the first n-type nitride semiconductor layer 2, for example, a nitride semiconductor crystal doped with an n-type dopant can be used.

In the above, as the light emitting layer 3, for example, a nitride semiconductor crystal having a single quantum well (SQW) structure or a multiple quantum well (MQW) structure can be grown. Among them, Al _a In _b Ga _{1 -(a + b)} N having a multiple quantum well structure including a nitride semiconductor crystal represented by a composition formula of N (0≤a≤1, 0≤b≤1, 0≤1- (a + b) ≤1) It is preferable to use it. In the above composition formula, a represents the Al composition ratio, b represents the In composition ratio, and 1- (a + b) represents the Ga composition ratio.

  In the above, as the p-type nitride semiconductor layer 4, for example, a nitride semiconductor crystal doped with a p-type dopant can be used. In particular, a p-type GaN layer is grown on a p-type cladding layer containing Al. Can be used.

In the above, the p-type nitride semiconductor tunnel junction layer 5 is, for example, Al _x1 In _y1 Ga _{1-(x1 + y1)} N (0 ≦ x1 ≦ 1, 0 ≦ y1 ≦ 1, 0 ≦ 1- ( A material obtained by doping a nitride semiconductor crystal represented by the composition formula of x1 + y1) ≦ 1) with a p-type dopant can be used. In the above composition formula, x1 represents the Al composition ratio, y1 represents the In composition ratio, and 1- (x1 + y1) represents the Ga composition ratio.

The concentration of the p-type dopant in the p-type nitride semiconductor tunnel junction layer 5 is preferably 2 × 10 ¹⁹ / cm ³ or more. In this case, the driving voltage of the nitride semiconductor light emitting device of the present invention tends to decrease.

In the above, the n-type nitride semiconductor tunnel junction layer 6 may be, for example, Al _x2 In _y2 Ga _{1- (x2 + y2)} N (0 ≦ x2 ≦ 1, 0 ≦ y2 ≦ 1, 0 ≦ 1- ( A material obtained by doping a nitride semiconductor crystal represented by a composition formula of x2 + y2) ≦ 1) with a p-type dopant can be used. In the above composition formula, x2 represents the Al composition ratio, y2 represents the In composition ratio, and 1- (x2 + y2) represents the Ga composition ratio. In the above composition formula, x2 represents the Al composition ratio, y2 represents the In composition ratio, and 1- (x2 + y2) represents the Ga composition ratio.

When n-type nitride semiconductor tunnel junction layer 6 is a layer containing In, the concentration of n-type dopant in n-type nitride semiconductor tunnel junction layer 6 is less than 5 × 10 ¹⁹ / cm ^3. Is preferred. In this case, the driving voltage of the nitride semiconductor light emitting device of the present invention tends to decrease.

  Here, (i) when the p-type nitride semiconductor tunnel junction layer 5 is made of InGaN (indium gallium nitride), the n-type nitride semiconductor tunnel junction layer 6 is preferably made of GaN (gallium nitride), and (ii) It is preferable that both the p-type nitride semiconductor tunnel junction layer 5 and the n-type nitride semiconductor tunnel junction layer 6 are made of InGaN, and (iii) n-type nitridation when the p-type nitride semiconductor tunnel junction layer 5 is made of GaN. The physical semiconductor tunnel junction layer 6 is preferably made of InGaN. The p-type nitride semiconductor tunnel junction layer 5 and the n-type nitride semiconductor tunnel junction layer 6 may be made of InGaN having different In contents. In each of the cases (i) to (iii), GaN may be AlGaN.

  In the present invention, at least one of p-type nitride semiconductor tunnel junction layer 5 and n-type nitride semiconductor tunnel junction layer 6 needs to be a layer containing In.

  In addition, by forming the n-type nitride semiconductor evaporation suppression layer 10, when the p-type nitride semiconductor tunnel junction layer 5 and / or the n-type nitride semiconductor tunnel junction layer 6 contains In, the In is contained from these layers. Evaporation can be suppressed.

Here, the n-type nitride semiconductor evaporation suppressing layer 10, for _{example, Al c In d Ga 1- (} c + d) N (0 ≦ c ≦ 1,0 ≦ d ≦ 1,0 ≦ 1- (c + d) A layer in which a nitride semiconductor crystal represented by the composition formula ≦ 1) is doped with an n-type dopant can be used, and among these, n-type GaN is preferably used. In the above composition formula, c represents the composition ratio of Al, d represents the composition ratio of In, and 1- (c + d) represents the composition ratio of Ga. The n-type nitride semiconductor evaporation suppression layer 10 is preferably grown at a temperature comparable to that of the p-type nitride semiconductor tunnel junction layer 5 and / or the n-type nitride semiconductor tunnel junction layer 6.

  Further, by forming the second n-type nitride semiconductor layer 7, the current injected from the p-side electrode 9 formed on the second n-type nitride semiconductor layer 7 can be diffused.

Here, as the second n-type nitride semiconductor layer 7, for example, a nitride semiconductor crystal doped with an n-type dopant can be used, and in particular, a layer having a low resistivity is preferable. The carrier concentration is preferably 1 × 10 ¹⁸ / cm ³ or more. In order to ensure high light extraction efficiency, the band gap of the second n-type nitride semiconductor layer 7 is preferably larger than the band gap of the light emitting layer 3.

  Examples of the n-side electrode 8 formed on the first n-type nitride semiconductor layer 2 and the p-side electrode 9 formed on the second n-type nitride semiconductor layer 7 include Ti (titanium), Hf It is preferable to form an ohmic contact using at least one metal selected from the group consisting of (hafnium) and Al (aluminum).

  Here, the n-side electrode 8 is formed by etching the wafer after the growth of the second n-type nitride semiconductor layer 7 from the second n-type nitride semiconductor layer 7 side. A part of the surface of the semiconductor layer 2 can be exposed and formed on the exposed surface.

  Further, the first n-type nitride semiconductor layer 7 side of the wafer after the growth of the second n-type nitride semiconductor layer 7 is attached to a separately prepared conductive support substrate, whereby the first n-type nitride semiconductor layer 7 side is attached. At least one selected from the group consisting of Al, Pt, and Ag having high reflectivity on the support substrate side, where the type nitride semiconductor layer 2 side is the light extraction side, and the second n-type nitride semiconductor layer 7 side is the support substrate side It is also possible to form a nitride semiconductor light emitting diode element having an upper and lower electrode structure by forming a seed metal.

  According to the nitride semiconductor light-emitting diode element having such an upper and lower electrode structure, the second n-type nitride semiconductor layer 7 can have a higher carrier concentration than the conventional p-type nitride semiconductor layer. Regardless of the work function, ohmic characteristics due to carrier tunneling can be easily obtained, and the above-described highly reflective metal can be formed on the second n-type nitride semiconductor layer 7, thereby improving light extraction efficiency. There is a tendency.

  In the present invention, the n-type dopant is preferably doped with at least one selected from the group consisting of Si (silicon), Ge (germanium) and O (oxygen).

  In the present invention, as the p-type dopant, for example, Mg (magnesium) and / or Zn (zinc) can be doped.

Example 1
In Example 1, a nitride semiconductor light-emitting diode element having the configuration shown in the schematic cross-sectional view of FIG. 2 was produced.

  First, the sapphire substrate 101 was set in a reaction furnace of a MOCVD (Metal Organic Chemical Vapor Deposition) apparatus. Then, the surface of the sapphire substrate 101 (C surface) was cleaned by raising the temperature of the sapphire substrate 101 to 1050 ° C. while flowing hydrogen into the reactor.

  Next, the temperature of the sapphire substrate 101 is lowered to 510 ° C., hydrogen as a carrier gas, ammonia and TMG (trimethyl gallium) as a source gas are flowed into the reactor, and GaN is formed on the surface (C plane) of the sapphire substrate 101. The buffer layer 102 was grown on the sapphire substrate 101 with a thickness of about 20 nm by MOCVD.

Next, the temperature of the sapphire substrate 101 is raised to 1050 ° C., hydrogen as a carrier gas, ammonia and TMG as source gases, and silane as an impurity gas are flown into the reaction furnace, and an n-type GaN underlayer 103 doped with Si is added. (Carrier concentration: 1 × 10 ¹⁸ / cm ³ ) was grown on the GaN buffer layer 102 to a thickness of 6 μm by MOCVD.

Subsequently, the n-type GaN contact layer 104 is formed to a thickness of 0.5 μm by MOCVD in the same manner as the n-type GaN underlayer 103 except that Si is doped so that the carrier concentration becomes 5 × 10 ¹⁸ / cm ^3. Then, it was grown on the n-type GaN foundation layer 103.

Next, the temperature of the sapphire substrate 101 is lowered to 700 ° C., nitrogen as a carrier gas, ammonia, TMG, and TMI (trimethylindium) as a source gas are flown into the reactor, and 2. on the n-type GaN contact layer 104. A light emitting layer 105 having a multiple quantum well structure is formed on the n-type GaN contact layer 104 by alternately growing an In _0.25 Ga _0.75 N layer having a thickness of 5 nm and a GaN layer having a thickness of 18 nm by a six-period MOCVD method. Formed. Needless to say, when the GaN layer is grown during the formation of the light emitting layer 105, TMI is not allowed to flow into the reactor.

Next, the temperature of the sapphire substrate 101 is raised to 950 ° C., hydrogen as a carrier gas, ammonia, TMG and TMA (trimethylaluminum) as source gases, and CP2Mg (cyclopentadienylmagnesium) as impurity gases are flowed into the reactor. A p-type AlGaN cladding layer 106 made of Al _0.15 Ga _0.85 N doped with Mg at a concentration of 1 × 10 ²⁰ / cm ³ was grown on the light-emitting layer 105 to a thickness of about 30 nm by MOCVD.

Next, while maintaining the temperature of the sapphire substrate 101 at 950 ° C., hydrogen as a carrier gas, ammonia and TMG as source gases, and CP2Mg as an impurity gas are allowed to flow into the reactor so that Mg is 1 × 10 ²⁰ / cm ^3. A p-type GaN contact layer 107 made of GaN doped with a concentration of 0.1 μm was grown on the p-type AlGaN cladding layer 106 by MOCVD.

Thereafter, the temperature of the sapphire substrate 101 is lowered to 750 ° C., nitrogen as the carrier gas, ammonia, TMG and TMI as the source gas, and CP2Mg as the impurity gas are flown into the reactor, and Mg is 1 × 10 ²⁰ / cm ³ . A p-type tunnel junction layer 108 (concentration of p-type dopant: 1 × 10 ²⁰ / cm ³ ) made of In _0.25 Ga _0.75 N doped at a concentration is formed to a thickness of 20 nm on the p-type GaN contact layer 107 by MOCVD. Grown up. Here, the band gap of the p-type GaN contact layer 107 is larger than the band gap of the p-type tunnel junction layer 108.

Thereafter, while maintaining the temperature of the sapphire substrate 101 at 750 ° C., nitrogen as the carrier gas, ammonia and TMG as the source gas, and silane as the impurity gas are allowed to flow into the reaction furnace so that Si is 1 × 10 ¹⁹ / cm ³ . An n-type tunnel junction layer 109 (concentration of n-type dopant: 1 × 10 ¹⁹ / cm ³ ) made of GaN doped at a concentration was grown to a thickness of 15 nm on the p-type tunnel junction layer 108 by MOCVD.

Thereafter, the temperature of the sapphire substrate 101 is increased to 950 ° C., hydrogen as a carrier gas, ammonia and TMG as source gases, and silane as an impurity gas are allowed to flow into the reaction furnace so that Si has a concentration of 1 × 10 ¹⁹ / cm ³ . The n-type GaN layer 111 made of GaN doped with the above was grown on the n-type tunnel junction layer 109 to a thickness of 0.2 μm by MOCVD.

  Next, the temperature of the sapphire substrate 101 was lowered to 700 ° C., and annealing was performed by flowing nitrogen as a carrier gas into the reaction furnace.

  Then, the annealed wafer was taken out of the reaction furnace, and a mask patterned in a predetermined shape was formed on the surface of the n-type GaN layer 111 as the uppermost layer of the wafer. Then, a part of the wafer was etched from the n-type GaN layer 111 side by RIE (Reactive Ion Etching) method to expose a part of the surface of the n-type GaN contact layer 104.

  Then, a pad electrode 112 was formed on the surface of the n-type GaN layer 111, and a pad electrode 113 was formed on the surface of the n-type GaN contact layer 104. Here, the pad electrode 112 and the pad electrode 113 were simultaneously formed by sequentially laminating a Ti layer and an Al layer on the surface of the n-type GaN layer 111 and the surface of the n-type GaN contact layer 104, respectively. Then, the nitride semiconductor light-emitting diode device of Example 1 having the configuration shown in the schematic cross-sectional view of FIG. 2 was manufactured by dividing the wafer into a plurality of chips.

  FIG. 3 shows the relationship between the thickness (nm) of the p-type tunnel junction layer 108 of the nitride semiconductor light-emitting diode element of Example 1 and the drive voltage (V). Here, in the nitride semiconductor light emitting diode element of Example 1, the p-type tunnel junction layer 108 corresponds to a layer containing In. Further, in the nitride semiconductor light emitting diode element of Example 1, the p-type tunnel junction layer 108 has a thickness between the p-type tunnel junction layer 108 and a layer having a larger band gap (p-type GaN contact layer 107). This corresponds to the shortest distance between the interface and the interface between the p-type tunnel junction layer 108 and the n-type tunnel junction layer 109. The drive voltage is when the injection current is 20 mA.

  As is apparent from FIG. 3, in the nitride semiconductor light emitting diode element of Example 1, the shortest distance (the thickness of the p-type tunnel junction layer 108) is less than 40 nm, preferably 20 nm or less, particularly 15 nm or less. In this case, it was confirmed that the driving voltage was significantly reduced. Further, it was confirmed that in the nitride semiconductor light emitting diode element of Example 1, the driving voltage tends to decrease as the shortest distance (the thickness of the p-type tunnel junction layer 108) decreases.

(Example 2)
In Example 2, a nitride semiconductor light-emitting diode element having the configuration shown in the schematic cross-sectional view of FIG. 2 was produced.

  Up to the point where the p-type GaN contact layer 107 was grown, it was fabricated under the same conditions and the same method as in Example 1.

Then, after the growth of the p-type GaN contact layer 107, the temperature of the sapphire substrate 101 is lowered to 750 ° C., nitrogen as a carrier gas, ammonia, TMG and TMI as source gases, and CP2Mg as an impurity gas flow into the reactor, Mg is 1 × 10 ²⁰ / cm consisting of doped in _0.1 Ga _0.9 N at a concentration of ³ p-type tunnel (concentration of p-type dopant: 1 × 10 ²⁰ / cm ³⁾ bonding layer 108 p-type GaN by the MOCVD method A thickness of 10 nm was grown on the contact layer 107. Here, the band gap of the p-type GaN contact layer 107 is larger than the band gap of the p-type tunnel junction layer 108. Further, in the nitride semiconductor light emitting diode element of Example 2, the p-type tunnel junction layer 108 has a thickness between the p-type tunnel junction layer 108 and a layer having a larger band gap (p-type GaN contact layer 107). This corresponds to the shortest distance between the interface and the interface between the p-type tunnel junction layer 108 and the n-type tunnel junction layer 109.

  Thereafter, the nitride semiconductor light-emitting diode element of Example 2 was fabricated under the same conditions and the same method as in Example 1.

When the injection current of the nitride semiconductor light emitting diode element of Example 2 is 20 mA, the driving voltage is higher than when the thickness of the p-type tunnel junction layer 108 of the nitride semiconductor light emitting diode element of Example 1 is 10 nm. It was confirmed.

(Example 3)
In Example 3, a nitride semiconductor light-emitting diode element having the configuration shown in the schematic cross-sectional view of FIG. 2 was produced.

  Up to the point where the p-type GaN contact layer 107 was grown, it was fabricated under the same conditions and the same method as in Example 1.

After the growth of the p-type GaN contact layer 107, the temperature of the sapphire substrate 101 is lowered to 650 ° C., nitrogen as a carrier gas, ammonia, TMG and TMI as source gases, and CP2Mg as an impurity gas flow into the reactor, Mg is 1 × 10 ²⁰ / cm consisting of doped in _0.5 Ga _0.5 N at a concentration of ³ p-type tunnel (concentration of p-type dopant: 1 × 10 ²⁰ / cm ³⁾ bonding layer 108 p-type GaN by the MOCVD method The contact layer 107 was grown to an arbitrary thickness within the range of 2 to 10 nm. Here, the band gap of the p-type GaN contact layer 107 is larger than the band gap of the p-type tunnel junction layer 108.

  Thereafter, the nitride semiconductor light-emitting diode device of Example 3 was fabricated under the same conditions and the same method as in Example 1.

  FIG. 4 shows the relationship between the thickness (nm) of the p-type tunnel junction layer 108 of the nitride semiconductor light-emitting diode element of Example 3 and the drive voltage (V). Here, in the nitride semiconductor light emitting diode element of Example 3, the p-type tunnel junction layer 108 corresponds to a layer containing In. Also in the nitride semiconductor light-emitting diode element of Example 3, the p-type tunnel junction layer 108 has a p-type tunnel junction layer 108 and a layer having a larger band gap (p-type GaN contact layer 107). This corresponds to the shortest distance between the interface and the interface between the p-type tunnel junction layer 108 and the n-type tunnel junction layer 109. The drive voltage is when the injection current is 20 mA.

  As is apparent from FIG. 4, in the nitride semiconductor light emitting diode device of Example 3, when the shortest distance (p-type tunnel junction layer 108 thickness) is 10 nm or less, preferably 4 nm or more and 6 nm or less. It was confirmed that the driving voltage was greatly reduced. In the nitride semiconductor light-emitting diode device of Example 3, the driving voltage was minimized when the shortest distance (the thickness of the p-type tunnel junction layer 108) was 6 nm.

  Further, in the nitride semiconductor light emitting diode device of Example 3, the driving voltage when the shortest distance (the thickness of the p-type tunnel junction layer 108) was 2 nm was higher than that at 6 nm. The shortest distance (thickness of the p-type tunnel junction layer 108) was smaller than the driving voltage when it was 40 nm or more.

Example 4
In Example 4, a nitride semiconductor light-emitting diode element having the configuration shown in the schematic cross-sectional view of FIG. 5 was produced.

  Up to the point where the p-type GaN contact layer 107 was grown, it was fabricated under the same conditions and the same method as in Example 1.

Then, after the growth of the p-type GaN contact layer 107, the temperature of the sapphire substrate 101 is lowered to 750 ° C., nitrogen as a carrier gas, ammonia, TMG and TMI as source gases, and CP2Mg as an impurity gas flow into the reactor, A p-type GaN tunnel junction layer 108 made of In _0.25 Ga _0.75 N doped with Mg at a concentration of 1 × 10 ²⁰ / cm ³ (p-type dopant concentration: 1 × 10 ²⁰ / cm ³ ) is formed by p-type GaN by MOCVD. A thickness of 5 nm was grown on the contact layer 107. Here, the band gap of the p-type GaN contact layer 107 is larger than the band gap of the p-type tunnel junction layer 108.

Thereafter, while maintaining the temperature of the sapphire substrate 101 at 750 ° C., nitrogen as a carrier gas, ammonia as a source gas, TMI and TMG, and silane as an impurity gas are allowed to flow into the reactor so that Si becomes 1 × 10 ¹⁹ / cm 3. ^An n-type tunnel junction layer 109 (concentration of n-type dopant: 1 × 10 ¹⁹ / cm ³ ) made of In _0.25 Ga _0.75 N doped at a concentration of ³ is deposited on the p-type tunnel junction layer 108 by a MOCVD method to a thickness of 15 nm. I grew up.

Next, while maintaining the temperature of the sapphire substrate 101 at 750 ° C., nitrogen as a carrier gas, ammonia and TMG as source gases, and silane as an impurity gas are allowed to flow into the reaction furnace so that Si becomes 1 × 10 ¹⁹ / cm ^3. An n-type GaN evaporation suppression layer 110 made of GaN doped at a concentration of 15 nm was grown on the n-type tunnel junction layer 109 to a thickness of 15 nm by MOCVD. Here, the band gap of the n-type GaN evaporation suppression layer 110 is larger than the band gap of the n-type tunnel junction layer 109.

Thereafter, the temperature of the sapphire substrate 101 is increased to 950 ° C., hydrogen as a carrier gas, ammonia and TMG as source gases, and silane as an impurity gas are allowed to flow into the reaction furnace so that Si has a concentration of 1 × 10 ¹⁹ / cm ³ . The n-type GaN layer 111 made of GaN doped in step 1 was grown on the n-type GaN evaporation suppression layer 110 to a thickness of 0.2 μm by MOCVD.

  Thereafter, the nitride semiconductor light-emitting diode device of Example 4 was fabricated under the same conditions and the same method as in Example 1.

  It is confirmed that the driving voltage of the nitride semiconductor light-emitting diode element of Example 4 is approximately the same as the driving voltage when the thickness of the p-type tunnel junction layer 108 of the nitride semiconductor light-emitting diode element of Example 1 is 10 nm. It was done.

Further, Si of the n-type tunnel junction layer 109 of the nitride semiconductor light-emitting diode device of Example 4 was doped at a concentration of 5 × 10 ¹⁹ / cm ³ (concentration of n-type dopant: 5 × 10 ¹⁹ / cm ³ The driving voltage of the nitride semiconductor light-emitting diode device produced by doping Si in the n-type tunnel junction layer 109 at a concentration of 1 × 10 ¹⁹ / cm ³ (concentration of n-type dopant: 1 × 10 ¹⁹ / cm ^3). It was confirmed that the driving voltage was higher than that of the nitride semiconductor light emitting diode device of Example 4).

  In the nitride semiconductor light-emitting diode element of Example 4, the thickness of the p-type tunnel junction layer 108 and the thickness of the n-type tunnel junction layer 109 correspond to the shortest distance.

(Example 5)
In Example 5, a nitride semiconductor light-emitting diode element having the configuration shown in the schematic cross-sectional view of FIG. 5 was produced.

  Up to the point where the p-type GaN contact layer 107 was grown, it was fabricated under the same conditions and the same method as in Example 1.

While keeping the temperature of the sapphire substrate 101 at 750 ° C., nitrogen as a carrier gas, ammonia, TMI and TMG as source gases, and silane as an impurity gas are allowed to flow into the reaction furnace so that Si is 1 × 10 ¹⁹ / cm ³ . An n-type tunnel junction layer 109 (concentration of n-type dopant: 1 × 10 ¹⁹ / cm ³ ) made of In _0.25 Ga _0.75 N doped at a concentration is formed to a thickness of 10 nm on the p-type GaN contact layer 107 by MOCVD. Grown up. Here, a part of the p-type GaN contact layer 107 on the n-type tunnel junction layer 109 side functions as the p-type tunnel junction layer 108.

Next, while maintaining the temperature of the sapphire substrate 101 at 750 ° C., nitrogen as a carrier gas, ammonia and TMG as source gases, and silane as an impurity gas are allowed to flow into the reaction furnace so that Si becomes 1 × 10 ¹⁹ / cm ^3. An n-type GaN evaporation suppression layer 110 made of GaN doped at a concentration of 15 nm was grown on the n-type tunnel junction layer 109 to a thickness of 15 nm by MOCVD. Here, the band gap of the n-type GaN evaporation suppression layer 110 is larger than the band gap of the n-type tunnel junction layer 109.

Thereafter, the temperature of the sapphire substrate 101 is increased to 950 ° C., hydrogen as a carrier gas, ammonia and TMG as source gases, and silane as an impurity gas are allowed to flow into the reaction furnace so that Si has a concentration of 1 × 10 ¹⁹ / cm ³ . The n-type GaN layer 111 made of GaN doped in step 1 was grown on the n-type GaN evaporation suppression layer 110 to a thickness of 0.2 μm by MOCVD.

  Then, a nitride semiconductor light-emitting diode element of Example 5 was fabricated under the same conditions and the same method as in Example 1.

  It is confirmed that the driving voltage of the nitride semiconductor light-emitting diode element of Example 5 is approximately the same as the driving voltage when the thickness of the p-type tunnel junction layer 108 of the nitride semiconductor light-emitting diode element of Example 1 is 10 nm. It was done.

In addition, the driving voltage of the nitride semiconductor light-emitting diode element manufactured by using the n-type GaN layer 111 of the nitride semiconductor light-emitting diode element of Example 5 as undoped is 1 × 10 ¹⁹ / cm ³ of Si in the n-type GaN layer 111. It was confirmed that the driving voltage of the nitride semiconductor light-emitting diode element of Example 5 manufactured by doping at the same level was comparable.

Further, the n-type tunnel junction layer 109 of the nitride semiconductor light-emitting diode device of Example 5 was fabricated by doping Si at a concentration of 5 × 10 ¹⁹ / cm ³ (concentration of n-type dopant: 5 × 10 ¹⁹ / cm ³ The driving voltage of the nitride semiconductor light-emitting diode device manufactured in Example 5 was prepared by doping Si in the n-type tunnel junction layer 109 at a concentration of 1 × 10 ¹⁹ / cm ^3. It was confirmed that it would be higher.

  In the nitride semiconductor light emitting diode element of Example 5, the thickness of the n-type tunnel junction layer 109 corresponds to the shortest distance.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  According to the present invention, the driving voltage of a nitride semiconductor light emitting element such as a nitride semiconductor light emitting diode element having a tunnel junction and emitting blue light (for example, a wavelength of 430 nm or more and 490 nm or less) can be reduced.

  1 substrate 2 first n-type nitride semiconductor layer 3 light emitting layer 4 p-type nitride semiconductor layer 5 p-type nitride semiconductor tunnel junction layer 6 n-type nitride semiconductor tunnel junction layer 7 second n-type nitride semiconductor layer, 8 p-side electrode, 9 n-side electrode, 10 n-type nitride semiconductor evaporation suppression layer, 101 sapphire substrate, 102 GaN buffer layer, 103 n-type GaN underlayer, 104 n-type GaN contact layer, 105 light emitting layer, 106 p-type AlGaN cladding layer, 107 p-type GaN contact layer, 108 p-type tunnel junction layer, 109 n-type tunnel junction layer, 110 n-type GaN evaporation suppression layer, 111 n-type GaN layer, 112, 113 pad electrode.

Claims (6)

A substrate, a first n-type nitride semiconductor layer, a light emitting layer, a p-type nitride semiconductor layer, a p-type nitride semiconductor tunnel junction layer, and an n-type nitride semiconductor tunnel formed on the substrate A bonding layer, an n-type nitride semiconductor evaporation suppression layer, and a second n-type nitride semiconductor layer,
The p-type nitride semiconductor tunnel junction layer and the n-type nitride semiconductor tunnel junction layer form a tunnel junction,
The p-type nitride semiconductor tunnel junction layer is p-type InGaN;
The n-type nitride semiconductor tunnel junction layer is n-type GaN,
One surface of the n-type nitride semiconductor tunnel junction layer is in contact with one surface of the p-type nitride semiconductor tunnel junction layer, and the other surface of the n-type nitride semiconductor tunnel junction layer is the n-type nitride semiconductor. In contact with the n-type nitride semiconductor evaporation suppression layer having a larger band gap than the tunnel junction layer,
The shortest of the interface between the n-type nitride semiconductor tunnel junction layer and the n-type nitride semiconductor evaporation suppression layer and the interface between the p-type nitride semiconductor tunnel junction layer and the n-type nitride semiconductor tunnel junction layer The distance is less than 40 nm,
The p-type nitride semiconductor tunnel junction layer has a thickness of 4 nm or more and 6 nm or less,
The nitride semiconductor light emitting device, wherein the n-type dopant concentration in the n-type nitride semiconductor tunnel junction layer is less than 5 × 10 ¹⁹ / cm ³ . 2. The nitride semiconductor light emitting device according to claim 1, wherein the n-type dopant is at least one selected from the group consisting of Si, Ge, and O. 3. ^3. The nitride semiconductor light emitting device according to claim 1, wherein a concentration of the p-type dopant in the p-type nitride semiconductor tunnel junction layer is 2 × 10 ¹⁹ / cm ³ or more. A substrate, a first n-type nitride semiconductor layer, a light emitting layer, a p-type nitride semiconductor layer, a p-type nitride semiconductor tunnel junction layer, and an n-type nitride semiconductor tunnel formed on the substrate A bonding layer, an n-type nitride semiconductor evaporation suppression layer, and a second n-type nitride semiconductor layer,
The p-type nitride semiconductor tunnel junction layer and the n-type nitride semiconductor tunnel junction layer form a tunnel junction,
The p-type nitride semiconductor tunnel junction layer is p-type InGaN;
The n-type nitride semiconductor tunnel junction layer is n-type GaN,
One surface of the n-type nitride semiconductor tunnel junction layer is in contact with one surface of the p-type nitride semiconductor tunnel junction layer, and the other surface of the n-type nitride semiconductor tunnel junction layer is the n-type nitride semiconductor. In contact with the n-type nitride semiconductor evaporation suppression layer having a larger band gap than the tunnel junction layer,
The other surface of the p-type nitride semiconductor tunnel junction layer is in contact with the p-type nitride semiconductor layer having a larger band gap than the p-type nitride semiconductor tunnel junction layer;
The shortest of the interface between the n-type nitride semiconductor tunnel junction layer and the n-type nitride semiconductor evaporation suppression layer and the interface between the p-type nitride semiconductor tunnel junction layer and the n-type nitride semiconductor tunnel junction layer The distance is less than 40 nm,
The p-type nitride semiconductor tunnel junction layer has a thickness of 4 nm or more and 6 nm or less,
The nitride semiconductor light emitting device, wherein the n-type dopant concentration in the n-type nitride semiconductor tunnel junction layer is less than 5 × 10 ¹⁹ / cm ³ . The nitride semiconductor light emitting device according to claim 4, wherein the n-type dopant is at least one selected from the group consisting of Si, Ge, and O. 6. The nitride semiconductor light emitting device according to claim 4 , wherein a concentration of the p-type dopant in the p-type nitride semiconductor tunnel junction layer is 2 × 10 ¹⁹ / cm ³ or more.

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