JP5305588B2 - GaN-based light emitting device and manufacturing method thereof - Google Patents

Description

  In the present invention, an n-type GaN-based semiconductor layer (hereinafter also referred to as “n-type layer”) and a p-type GaN-based semiconductor layer (hereinafter also referred to as “p-type layer”) are made of a GaN-based semiconductor. The present invention relates to a GaN-based light-emitting device having a stacked structure with an active layer sandwiched therebetween, and a method for manufacturing the same, and in particular, GaN in which deterioration due to energization and improvement in resistance to electrostatic breakdown are simultaneously achieved. The present invention relates to a system light emitting device and a method for manufacturing such a GaN light emitting device.

A GaN-based semiconductor is a compound semiconductor having a composition determined by the chemical formula Al _a In _b Ga _1-ab N (0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ a + b ≦ 1). It is also called a compound semiconductor, a group III nitride compound semiconductor, and the like. The GaN-based semiconductor includes, for example, those having an arbitrary composition such as GaN, InGaN, AlGaN, AlInGaN, AlN, and InN. In the above chemical formula, a part of the group 3 element is B (boron), Tl (thallium). In addition, those in which a part of N (nitrogen) is substituted with P (phosphorus), As (arsenic), Sb (antimony), Bi (bismuth), or the like are also included in the GaN-based semiconductor.

  A GaN-based light emitting device is formed on a substrate made of sapphire or the like by using a vapor phase growth method such as an organic metal compound vapor phase growth (MOVPE) method, a hydride vapor phase growth (HVPE) method, or a molecular beam epitaxy (MBE) method. In addition, an n-type layer, an active layer, and a p-type layer are sequentially grown and stacked, and an electrode is formed on each of the n-type layer and the p-type layer.

  Patent Document 1 discloses a GaN-based light-emitting element in which an active layer and a p-type layer are sequentially grown on an n-type layer having pits for the purpose of improving the light emission output. A technique for growing a GaN-based semiconductor so that no pits are formed has been well known before the invention of the GaN-based light-emitting element of Patent Document 1, but in the GaN-based light-emitting element, during the growth of the n-type layer, The pits are intentionally formed on the surface of the n-type layer by lowering the growth temperature from the normal temperature to a temperature lower than the normal temperature. FIG. 4 is a cross-sectional view showing the structure of a GaN-based light emitting device manufactured by such a conventional technique. The device 100 includes a sapphire substrate 10, a buffer layer (not shown), an undoped GaN layer 11, and an n-type GaN cladding layer. 12A, an n-type GaN clad layer 12B formed with pits, an active layer 13, a p-type AlGaN clad layer 14, a p-type GaN contact layer 15, an n-side electrode P11, a p-side electrode P12, and a pad electrode P13. . In the manufacturing process of the GaN-based light emitting device 100, the n-type GaN cladding layer 12A is preferably grown at a growth temperature of 1000 ° C. or higher so that no pits are formed, and the n-type GaN cladding layer 12B is formed with pits. Thus, it is grown at a low growth temperature (included in the region of 500 ° C. to 950 ° C.). Hereinafter, in this specification, an n-type layer grown so as to form pits is grown at the first temperature by lowering the growth temperature from the first temperature to the second temperature during the growth. This layer will be referred to as the “high temperature n-type layer”, and the layer grown at the second temperature will be referred to as the “low temperature n-type layer”. In the GaN-based light emitting device 100, the n-type GaN cladding layer 12A corresponds to a high-temperature n-type layer, and the n-type GaN cladding layer 12B in which pits are formed corresponds to a low-temperature n-type layer.

JP-A-11-220169

  The GaN-based light emitting device 100 shown in FIG. 4 has extremely low resistance to electrostatic breakdown unless the n-type GaN cladding layer 12B, which is a low-temperature n-type layer, is doped with an n-type impurity to impart conductivity. The present inventors have found that, when this layer is doped with n-type impurities, the resistance against electrostatic breakdown is improved, but deterioration due to energization is accelerated.

  The present invention has been made to solve the above-described problems, and provides a GaN-based light emitting device capable of simultaneously suppressing deterioration due to energization and improving resistance to electrostatic breakdown, and a method for manufacturing the same. The purpose is to do.

The GaN-based light emitting device and the GaN-based light emitting device manufacturing method of the present invention have the following characteristics.
(1) A step of growing an n-type layer so that pits are formed by lowering the growth temperature from the first temperature to the second temperature during the growth, and an active layer is formed on the n-type layer. A step of growing and a step of growing a p-type layer on the active layer. Of the n-type layer, a layer grown at a first temperature is a high-temperature n-type layer, and a second temperature is When the layer grown in step 1 is a low-temperature n-type layer, the step of growing the low-temperature n-type layer includes the step of forming a first region in contact with the high-temperature n-type layer, and the step of forming the first region above the first region. Forming a second region at a position away from the high-temperature n-type layer, wherein the first region is formed such that the n-type impurity concentration is lower than that of the second region, and the second region is formed. Is formed so that the n-type impurity concentration is higher than that of the active layer, and the active layer is in contact with the n-type layer. , A method of manufacturing a GaN-based light emitting device characterized be grown, that as a pit on its upper surface is open.
(2) The manufacturing method according to (1), wherein the first region includes a GaN-based semiconductor grown undoped.
(3) In the above (1) or (2), the second region includes a GaN-based semiconductor to which an n-type impurity is added at a concentration of 5 times or more the maximum value of the n-type impurity concentration in the active layer. The manufacturing method as described.
(4) The high-temperature n-type layer includes a high carrier concentration layer having an n-type impurity concentration of 2 × 10 ¹⁸ cm ⁻³ or more, and the second region is a maximum value of the n-type impurity concentration in the high carrier concentration layer. The manufacturing method in any one of said (1)-(3) containing the GaN-type semiconductor to which an n-type impurity is added to the density | concentration of 50% or more.
(5) A step of growing the n-type layer so that pits are formed by lowering the growth temperature from the first temperature to the second temperature during the growth, and an active layer is formed on the n-type layer. A step of growing and a step of growing a p-type layer on the active layer. Of the n-type layer, a layer grown at a first temperature is a high-temperature n-type layer, and a second temperature is When the layer grown in step 1 is a low-temperature n-type layer, the step of growing the low-temperature n-type layer includes the step of forming a first layer in contact with the high-temperature n-type layer, and the step of Forming a second layer at a position away from the high-temperature n-type layer, wherein the first layer is formed so that the n-type impurity concentration is lower than that of the second layer, and the second layer is formed. Is formed so that the n-type impurity concentration is higher than that of the active layer, and the active layer is in contact with the n-type layer and has an upper surface thereof Pits grown so as to open, a method of manufacturing a GaN-based light emitting device characterized by.
(6) The manufacturing method according to (5), wherein the first layer is a GaN-based semiconductor layer grown undoped.
(7) The manufacturing method according to (5) or (6), wherein the first layer and the second layer are formed to overlap each other.
(8) The second layer according to any one of (5) to (7), wherein an n-type impurity is added to a concentration of 5 times or more a maximum value of the n-type impurity concentration in the active layer. Production method.
(9) The high-temperature n-type layer includes a high carrier concentration layer having an n-type impurity concentration of 2 × 10 ¹⁸ cm ⁻³ or more, and the second layer has a maximum n-type impurity concentration in the high carrier concentration layer. The manufacturing method according to any one of (5) to (8), wherein an n-type impurity is added to a concentration of 50% or more of the value.
(10) The manufacturing method according to any one of (1) to (9), wherein the low-temperature n-type layer is formed of GaN or AlGaN.
(11) The manufacturing method according to any one of (1) to (10), wherein the high-temperature n-type layer and the low-temperature n-type layer are formed of a GaN-based semiconductor having the same crystal composition.
(12) The manufacturing method according to any one of (1) to (11), wherein the active layer is grown on an upper surface thereof so that pits having a depth larger than the film thickness of the active layer are opened.
(13) A GaN-based light emitting device manufactured by the manufacturing method according to any one of (1) to (12).

  By using the method for manufacturing a GaN-based light emitting device of the present invention, it is possible to obtain a GaN-based light emitting device in which suppression of deterioration due to energization and improvement in resistance to electrostatic breakdown are simultaneously achieved.

(Description of action)
In the conventional GaN-based light emitting device 100 shown in FIG. 4, when the n-type GaN cladding layer 12B is doped with an n-type impurity, the deterioration due to energization is accelerated because of the crystallinity of the n-type GaN cladding layer 12B. This is considered to be due to a significant decrease in the quality of the active layer 13 grown thereon. Therefore, in the GaN-based light emitting device according to the present invention, for example, as in the GaN-based light emitting device 200 shown in FIG. 1, the n-type GaN cladding layer 22B, which is a low-temperature n-type layer, is an n-type that causes a decrease in crystallinity. An undoped layer 22B-1 that is not doped with impurities and an n-doped layer 22B-2 that is doped with an n-type impurity concentration to provide conductivity. Although this n-type GaN cladding layer 22B is formed at a lower growth temperature than usual, the undoped layer 22B-1 is grown first, and the n-doped layer 22B-2 is stacked thereon, The decrease in crystallinity is suppressed, and as a result, the quality of the active layer 23 formed on the n-type GaN cladding layer 22B is also improved. It seems that it was late. Further, since the n-doped layer 22B-2 has an n-type impurity concentration higher than that of the active layer and higher conductivity than that of the active layer, the inside of the n-type GaN cladding layer 22B when a high voltage is applied to the element. Thus, it is considered that the GaN-based light emitting device 200 has improved resistance to electrostatic breakdown as compared with the case where the n-doped layer 22B-2 is not provided.

(Example)
Hereinafter, the present invention will be described based on specific examples.
FIG. 1 is a cross-sectional view of a GaN-based light emitting device 200 embodying the present invention. Reference numeral 20 denotes a sapphire substrate, on which an undoped GaN layer 21 is formed via a GaN buffer layer (not shown). On the undoped GaN layer 21, an n-type GaN cladding layer 22A having a film thickness of about 4 μm doped with Si (silicon) at a concentration of about 5 × 10 ¹⁸ cm ⁻³ is formed. On the n-type GaN clad layer 22A, an n-type GaN clad layer 22B having a thickness of 200 nm and having pits on the surface is formed. The n-type GaN clad layer 22B includes an undoped layer 22B-1 and an n-doped layer 22B-2 doped with Si at a concentration of about 5 × 10 ¹⁸ cm ⁻³ . The film thickness is 180 nm, and the film thickness of the n-doped layer 22B-2 is 20 nm. On the n-type GaN clad layer 22B, a seven-layer barrier layer and a six-well layer are alternately stacked so that the lowermost layer and the uppermost layer are barrier layers. An active layer 23 is formed. In the active layer 23, the barrier layer is an Si-doped GaN layer (Si concentration: about 5 × 10 ¹⁷ cm ⁻³ ) having a thickness of 10 nm, and the well layer is an undoped InGaN layer (emission wavelength 400 nm) having a thickness of 5 nm. Thus, the n-type impurity concentration (about 5 × 10 ¹⁸ cm ⁻³ ) of the n-doped layer 22B-2 is higher than the n-type impurity concentration (about 5 × 10 ¹⁷ cm ⁻³ ) of the active layer 23. High concentration. A p-type AlGaN cladding layer 24 having a thickness of 30 nm made of Al _0.1 Ga _0.9 N doped with Mg (magnesium) is formed on the active layer 23, and Mg is doped thereon. A p-type GaN contact layer 25 having a thickness of 150 nm is laminated. On the partially exposed surface of the n-type GaN clad layer 22A, an n-side electrode P1 is formed by laminating an Al (aluminum) layer on a Ti (titanium) layer and performing a heat treatment. On the upper surface of the p-type GaN contact layer 25, a p-side electrode P2 formed by laminating an Au (gold) layer on a Ni (nickel) layer and performing heat treatment is formed so as to cover the entire upper surface. ing. On the p-side electrode P2, a pad electrode P23 formed by laminating an Au layer on a Ti layer is formed.

  Next, a method for manufacturing the GaN-based light emitting device 200 will be described. The MOVPE method was used as the vapor phase growth method of the GaN-based semiconductor layer, but the growth technology of the GaN-based semiconductor crystal using the MOVPE method is known, and the apparatus (growth furnace, control system, piping system), raw material, carrier For the gas and basic growth conditions, the prior art can be referred to as appropriate.

First, a sapphire substrate 20 having a C-plane as a main surface was prepared, and this was mounted on a susceptor provided in a growth furnace of a MOVPE apparatus. Then, while supplying hydrogen gas into the growth furnace, the sapphire substrate 20 was heated to 1100 ° C. or higher to remove organic contamination on the substrate surface. Then, the substrate temperature was lowered to 500 ° C., and trimethylgallium (TMG) and ammonia were supplied as raw materials to form a GaN buffer layer. After the formation of the GaN buffer layer, the substrate temperature was raised to 1000 ° C. and TMG and ammonia were supplied to form an undoped GaN layer 21 having a thickness of about 2 μm. Next, TMG, ammonia, and silane (SiH ₄ ) were supplied to form an n-type GaN cladding layer 22A. This n-type GaN cladding layer 22A corresponds to a high-temperature n-type layer.

  Next, the substrate temperature was lowered to 750 ° C. to form an n-type GaN clad layer 22B having pits. This n-type GaN cladding layer 22B corresponds to a low-temperature n-type layer. The n-type GaN clad layer 22B first supplies TMG and ammonia to grow the undoped layer 22B-1 by 180 nm, and then supplies TMG, ammonia and silane to grow the n-doped layer 22B-2 by 20 nm. To form. Note that, after the growth of the n-type GaN cladding layer 22B was performed, the substrate heating was stopped and the sample prepared by lowering the temperature to room temperature in an ammonia atmosphere was observed using an atomic force microscope (AFM). Many pits having regular hexagonal openings were formed on the surface of the type GaN cladding layer 22B. As shown in FIG. 2, when the length of the diagonal line connecting two opposite corners of this regular hexagon is defined as “opening diameter”, the opening diameter of the pit formed in the n-type GaN cladding layer 22B is 0.1 μm to It was 0.2 μm.

  After forming the n-type GaN cladding layer, the active layer 23 was formed while maintaining the substrate temperature at 750 ° C. When forming the barrier layer, TMG, ammonia and silane were supplied, and when forming the well layer, TMG, trimethylindium and ammonia were supplied. In addition, after performing until the growth of the active layer 23, the substrate heating was stopped and the sample prepared by lowering the temperature to room temperature in an ammonia atmosphere was observed using an atomic force microscope (AFM). There were also many pits. The density of the pits (the average number of pits existing in the unit area) was substantially the same as the density of pits formed on the surface of the n-type GaN cladding layer 22B. Further, although the thickness of the active layer 23 is smaller than that of the n-type GaN cladding layer 22B, the opening diameter of pits on the surface of the active layer 23 is larger than the opening diameter of pits on the surface of the n-type GaN cladding layer 22B. Therefore, as schematically shown in FIG. 3, the pits observed on the surface of the active layer 23 are the pits formed on the n-type GaN cladding layer 22B, and the surface of the active layer 23 It is considered that the n-type GaN cladding layer 22B is reached. In other words, the depth of the pit is considered to be larger than the film thickness of the active layer 23.

Next, the substrate temperature was raised to 1025 ° C. while supplying ammonia. The temperature increase rate at this time was 110 ° C./min, and the temperature increase was completed in about 2.5 minutes. After the temperature increase, TMG, trimethylaluminum (TMA), biscyclopentadienylmagnesium (Cp ₂ Mg) and ammonia were supplied to form a p-type AlGaN cladding layer 24. In addition, after performing up to the said temperature rise, without forming the p-type AlGaN clad layer 24, a substrate heating was stopped, and the sample produced by temperature-falling to room temperature in ammonia atmosphere was made into the atomic force microscope (AFM). As a result of observation, the pits existing on the surface of the active layer 23 were buried, and the surface of the active layer 23 was in a highly flat state.

After forming the p-type AlGaN cladding layer 24, TMG, Cp ₂ Mg and ammonia were supplied to form the p-type contact layer 25. Thereafter, the substrate temperature was lowered to room temperature in an ammonia atmosphere, and the wafer was taken out of the MOVPE apparatus. Next, the wafer was subjected to an annealing process for activating Mg added as an impurity to the p-type layer. The formation of the n-side electrode P21, the p-side electrode P22, and the pad electrode P23, and the cutting of the chip from the wafer were performed using methods well known in this field. Thus, a chip-shaped GaN-based light emitting device 200 having a square top surface and a side length of 0.35 mm was obtained.

  When the reverse current that flows when a voltage of 5 V was applied in the reverse direction to the manufactured chip-like element was measured, it was less than 0.05 μA in the initial state before energization. Next, a current of 100 mA was continuously applied to the device in the forward direction for 50 hours, and after the deterioration, the reverse current was measured in the same manner. It was less than 5 μA. In addition, the resistance of an element in an initial state before energization to electrostatic breakdown is determined by a human body model (HBM) as defined in the standard for electrostatic breakdown test (ESTM standard STM5.1-1998). ), The majority of sample elements used for measurement (90% of the total number) were not destroyed at 2000 V or less.

(Comparative Example 1)
As Comparative Example 1, a chip-like GaN-based light emitting device was fabricated in the same manner as in the above example except that the entire n-type GaN cladding layer 22B was undoped, and in the same manner as in the above example, When the reverse current was measured after the initial state was deteriorated by flowing a current of 100 mA in the forward direction for 50 hours, it was less than 0.05 μA in the initial state and low as less than 0.1 μA even after the deterioration. Value. However, when the elements in the initial state before energization were evaluated for resistance to electrostatic breakdown by the same method as in the example, the total number of sample elements used for the measurement was destroyed at 150 V or less.

(Comparative Example 2)
As Comparative Example 2, a chip-like GaN-based light emitting device was fabricated in the same manner as in the above example, except that the entire n-type GaN cladding layer 22B was doped with Si at a concentration of about 5 × 10 ¹⁸ cm ^−3. Then, in the same manner as in the above example, the initial state before energization and the reverse current after degradation by flowing a current of 100 mA in the forward direction were measured. As a result, the reverse current flowing through the device was lower than that of the device of the example in the initial state, but it exceeded 1 μA after energization for 10 hours, and about 5 μA after 50 hours of energization. It increased to a value more than 10 times that of the device of the example. On the other hand, when the element in the initial state before energization was evaluated for resistance to electrostatic breakdown by the same method as in the example, it was equivalent to the element in the example.

  From the comparison between the example and the comparative example described above, it can be seen that, in the GaN-based light emitting device 200 according to the example, suppression of deterioration due to energization and improvement in resistance to electrostatic breakdown are achieved at the same time. .

As mentioned above, although this invention was demonstrated using the specific Example, this invention is not limited to the said Example. In the GaN-based light emitting device 200, the sapphire substrate 20 is used, but another substrate suitable for the growth of the GaN-based semiconductor crystal can be used without limitation instead of the sapphire substrate. A mask pattern made of SiO ₂ or the like may be formed on the crystal growth surface of the substrate before the GaN-based semiconductor layer is grown, or the uneven shape may be processed. The GaN-based light emitting device 200 includes the sapphire substrate 20 used for vapor phase growth of the GaN-based semiconductor layer, but is not essential. For example, after the vapor phase growth is completed, the sapphire substrate 20 is separately provided. You may replace with the prepared board | substrate.

  In the GaN-based light emitting device of the present invention, the stacked structure composed of the n-type layer, the active layer, and the p-type layer has a structure in which electrons injected into the n-type layer and holes injected into the p-type layer are regenerated in the active layer. It is only necessary that light emission is generated by bonding, and each layer can be formed of a GaN-based semiconductor having an arbitrary crystal composition. In order to increase the light emission efficiency, it is preferable to form a double hetero structure, and the active layer preferably has a quantum well structure (MQW, SQW). In the GaN-based light emitting device 200, the n-type GaN clad layer 22A also serves as a contact layer, but is not essential, and the clad layer and the contact layer may be provided as separate layers in the n-type layer. In the case where a conductive substrate is used, the n-side electrode can be formed on the substrate by omitting the contact layer from the n-type layer. In addition to the cladding layer and contact layer, a layer for controlling dislocation propagation, a layer for suppressing impurity diffusion, a layer for controlling light reflectivity and transparency, a layer for confining light, and light emission A layer having various functions such as a layer for protecting the layer may be provided as appropriate, and the n-type layer, the active layer, and the p-type layer may be configured so that all or part of them also serve as these functional layers. Can do. The configuration in which the undoped GaN layer 21 is interposed between the sapphire substrate 20 and the n-type GaN cladding layer 22A is not essential, but the crystallinity of the n-type GaN cladding layer 22A and the GaN-based semiconductor layer grown on the n-type GaN cladding layer 22A is not limited. This is a preferable configuration for improvement. A second n-type layer may be stacked on the p-type layer via a tunnel junction, and a p-side electrode may be formed on the second n-type layer.

  The growth temperature of the high-temperature n-type layer and the low-temperature n-type layer can be determined by appropriately referring to the description in Patent Document 1 and other conventional techniques. None of these temperatures need be constant. In the MOVPE method, the growth temperature of the high-temperature n-type layer is preferably 1000 ° C. to 1200 ° C., and the growth temperature of the low-temperature n-type layer is preferably 650 ° C. to 850 ° C. The opening diameter of the pits on the surface of the low-temperature n-type layer tends to increase as the growth temperature of the layer decreases and as the hydrogen partial pressure in the atmosphere during growth increases. The present inventors have found that even when the film thickness of the low-temperature n-type layer is too small, the light-emitting element tends to be deteriorated by energization, and from this, the film thickness of the low-temperature n-type layer is The thickness is preferably 100 nm or more, and more preferably 150 nm or more. Further, if the film thickness of the low-temperature n-type layer is excessively increased, the crystallinity of the active layer tends to be lowered. Therefore, the film thickness is preferably 600 nm or less.

  In the low-temperature n-type layer, a region doped with n-type impurities at a higher concentration than the active layer (hereinafter also referred to as “high-concentration region”) is provided in order to improve the resistance of the device to electrostatic breakdown. In order to improve the crystallinity of such a low-temperature n-type layer, at least a region of the low-temperature n-type layer in contact with the high-temperature n-type layer in which the n-type impurity concentration is lower than that of the high-concentration region ( Hereinafter, it may be referred to as a “low concentration region”). Accordingly, the low-temperature n-type layer may be doped with an n-type impurity such that the n-type impurity concentration monotonously increases with distance from the high-temperature n-type layer. For example, a layer having a three-layer structure in which a layer having a relatively high n-type impurity concentration is sandwiched between two layers having low levels may be used. Since the crystallinity of GaN-based semiconductors becomes better as the concentration of impurities contained is lower, the effect of improving the crystallinity of the low-temperature n-type layer by providing a low-concentration region is that the low-concentration region grows undoped. It becomes the maximum when it is formed of a GaN-based semiconductor. As can be seen from the above embodiment, even when the majority of the low-temperature n-type layer is formed of an undoped GaN-based semiconductor, a high-concentration region is formed so as to sandwich the portion between the high-temperature n-type layer. By providing, the resistance to electrostatic breakdown of the element can be dramatically improved.

By making the n-type impurity concentration in the high-concentration region of the low-temperature n-type layer preferably 5 times or more, more preferably 10 times or more the n-type impurity concentration of the active layer, the device has higher resistance to electrostatic breakdown. Can be. There is no particular upper limit to the n-type impurity concentration in the high-concentration region of the low-temperature n-type layer. The present inventors suppressed deterioration due to energization even when the concentration of Si added to the n-doped layer 22B-2 was increased to 2 × 10 ¹⁹ cm ^{−3 in} the configuration of the GaN-based light emitting device 200 of the above example. Is fully achieved.

As in the conventional GaN-based light emitting device described in Patent Document 1, an n-type impurity is added to the high-temperature n-type layer at a concentration of 2 × 10 ¹⁸ cm ⁻³ or more, and the film thickness is 2 μm or more. Generally, a high carrier concentration layer is provided. The n-type impurity concentration in the high-concentration region of the low-temperature n-type layer can be set based on the n-type impurity concentration in the high-carrier concentration layer. In the GaN-based light-emitting device having a configuration in which only the low-temperature n-type layer (n-type GaN cladding layer 22B) is omitted from the GaN-based light-emitting device 200 of the above embodiment, deterioration due to energization occurs in a very short time. It has been confirmed that the resistance to electrostatic breakdown is good. From this, the n-type impurity concentration in the high-concentration region of the low-temperature n-type layer is equal to or higher than the n-type impurity concentration in the high carrier concentration layer in the high-temperature n-type layer (the n-type impurity concentration in the high carrier concentration layer). 50% or more of the maximum value of the above) is preferable. More preferably, the n-type impurity concentration in the high-concentration region of the low-temperature n-type layer is the same as the maximum value of the n-type impurity concentration in the high-carrier concentration layer in the high-temperature n-type layer, as in the above embodiment. Or higher concentration.

  The low-temperature n-type layer may be formed of a GaN-based semiconductor having an arbitrary crystal composition. However, since the decomposition temperature of a GaN-based semiconductor containing a large amount of In (indium) is low, the low-temperature n-type layer is formed of GaN, AlGaN. In order to increase the heat resistance of the element, it is preferable to form a GaN-based semiconductor that does not contain In. Further, when the low-temperature n-type layer is formed of a GaN-based semiconductor containing In, the band gap is narrowed, so that the light absorption is increased. In particular, in the case of an element having a short emission wavelength (purple to ultraviolet light-emitting element), the output The influence on can not be ignored. In order to alleviate this problem, the low-temperature n-type layer is preferably formed of a GaN-based semiconductor such as GaN or AlGaN that does not contain In. In order to suppress a decrease in crystallinity of the low-temperature n-type layer, it is also effective to form the high-temperature n-type layer and the low-temperature n-type layer with a GaN-based semiconductor having the same crystal composition. More preferably, both the n-type layer and the low-temperature n-type layer are formed of GaN which is a binary crystal.

The following matters are added.
(1a) An n-type layer grown so that pits are formed by lowering the growth temperature from the first temperature to the second temperature during the growth, and active on the n-type layer A GaN-based light emitting device in which a layer and a p-type layer are sequentially grown, wherein a layer grown at a first temperature is a high-temperature n-type layer and a layer grown at a second temperature among the n-type layers Is a low-temperature n-type layer, the low-temperature n-type layer includes a first region provided in a portion in contact with the high-temperature n-type layer, and a position farther from the high-temperature n-type layer than the first region. The first region is provided such that the n-type impurity concentration is lower than that of the second region, and the second region is A GaN-based light emitting device provided so that an n-type impurity concentration is higher than that of the active layer.
(2a) The GaN-based light emitting device according to (1a), wherein the first region includes an undoped GaN-based semiconductor.
(3a) An n-type layer grown so that pits are formed by lowering the growth temperature from the first temperature to the second temperature in the middle of growth, and active on the n-type layer A GaN-based light emitting device in which a layer and a p-type layer are sequentially grown, wherein a layer grown at a first temperature is a high-temperature n-type layer and a layer grown at a second temperature among the n-type layers Is a low-temperature n-type layer, the low-temperature n-type layer includes a first layer provided in a portion in contact with the high-temperature n-type layer, and a position farther from the high-temperature n-type layer than the first layer. The first layer is provided such that the n-type impurity concentration is lower than that of the second layer, and the second layer includes: A GaN-based light emitting device provided so that an n-type impurity concentration is higher than that of the active layer.
(4a) The GaN-based light emitting device according to (3a), wherein the first layer is a GaN-based semiconductor layer grown undoped.
(5a) The GaN-based light emitting device according to (3a) or (4a), wherein the first layer and the second layer are formed to overlap each other.
(6a) The GaN-based light emitting device according to any one of (1a) to (5a), wherein the low-temperature n-type layer is made of GaN or AlGaN.
(7a) The GaN-based light-emitting element according to any one of (1a) to (6a), wherein the high-temperature n-type layer and the low-temperature n-type layer are made of a GaN-based semiconductor having the same crystal composition.

It is sectional drawing which shows the structure of the GaN-type light emitting element which implemented this invention. It is a figure explaining the opening diameter of a pit. It is sectional drawing which shows typically the mode of the growth of the active layer at the time of manufacture of the GaN-type light emitting element shown in FIG. It is sectional drawing which shows the structure of the GaN-type light emitting element of a prior art.

Explanation of symbols

100, 200 GaN-based light emitting device 10, 20 Sapphire substrate 11, 21 Undoped GaN layer 12A, 22A n-type GaN cladding layer 12B, 22B n-type GaN cladding layer 22B-1 undoped layer 22B-2 n-doped layer 13, 23 Active layer 14, 24 p-type AlGaN cladding layer 15, 25 p-type GaN contact layer P11, P21 n-side electrode P12, P22 p-side electrode P13, P23 pad electrode

Claims (2)

A step of growing an n-type layer so that pits are formed by lowering the growth temperature from the first temperature to the second temperature during the growth, and a step of growing an active layer on the n-type layer And growing a p-type layer on the active layer;
Have
Wherein among the n-type layer, the first high-temperature n-type layer a layer which is grown at a temperature of, when a layer is grown at the second temperature and a low temperature n-type layer,
The step of growing the low-temperature n-type layer includes a step of forming a first layer in contact with the high-temperature n-type layer, and a second layer at a position farther from the high-temperature n-type layer than the first layer. Forming a process,
The first layer is an undoped GaN-based semiconductor layer having an n-type impurity concentration lower than that of the second layer,
The second layer is a GaN-based semiconductor layer formed so that the n-type impurity concentration is higher than that of the active layer and the n-type impurity concentration is 5 × 10 ¹⁸ cm ⁻³ or more. ,
The method of manufacturing a GaN-based light emitting device, wherein the active layer is grown so as to be in contact with the n-type layer and have a pit opened on an upper surface thereof. A GaN-based light emitting device manufactured by the manufacturing method according to claim 1 .

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