JP3927646B2 - Gallium nitride compound semiconductor light emitting device and method for manufacturing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gallium nitride-based compound semiconductor light emitting device capable of emitting light from a green region to an ultraviolet region and a method for manufacturing the same.
[0002]
[Prior art]
As a conventional gallium nitride-based compound semiconductor light emitting device, there is a semiconductor laser as disclosed in, for example, Japanese Patent Application Laid-Open No. 8-97507, and FIG. This laser element is manufactured as follows. First, a buffer layer 802 made of n-type GaN, n-type Al on a sapphire substrate 801._zGa_1-zLower cladding layer 803 made of N (0 <z <1), In_xGa_1-xActive layer 804 made of N (0 <x <1), 1 × 10¹⁸cm^-3Al with p-type impurities of density_zGa_1-zUpper first cladding layer 805 made of N, 3 × 10¹⁸cm^-3Al containing n-type impurities with a density of_yGa_1-yA current blocking layer 806 (0 <y ≦ 1, z <y) made of N is stacked. Next, the wafer is taken out from the MOCVD apparatus and etched by a photolithography process to expose the upper first cladding layer 805 to form a current blocking layer 806 having a stripe groove 820. Thereafter, the wafer is again introduced into the MOCVD apparatus, and the substrate temperature is maintained at 1020 ° C. for a certain period of time._zGa_1-zAn upper second cladding layer 807 made of N and a contact layer 808 made of p-type GaN are formed to fill the stripe groove 820. Finally, etching that exposes the buffer layer 802 in a region that does not include the stripe groove 820 is performed to form a p-type electrode 809 and an n-type electrode 810, respectively.
[0003]
[Problems to be solved by the invention]
The conventional gallium nitride compound semiconductor light emitting device has the following problems.
(1) The element series resistance is increased to 20Ω or higher, and the drive voltage is increased to 5V or higher.
(2) The device life at a high temperature (at 60 ° C. atmosphere) is as short as about 500 hours due to heat generated by the series resistance.
(3) An element in which a negative resistance appears in the relationship between current and voltage appears, resulting in a decrease in manufacturing yield.
These problems have not been observed in laser elements made of other materials such as AlGaAs. As a result of detailed analysis of the conventional element, the inventor conducted recrystallization growth after forming a current blocking structure. Further, near the interface between the upper first cladding layer 805 and the upper second cladding layer 807, AlO_xIt was found that a redeposition layer 821 composed of an oxide film formed thereon and an n-type (or high resistance) AlGaN layer thereon was induced by being interposed at a thickness of about 13 nm.
[0004]
As a result of analyzing the process in more detail, the redeposition layer 821 is necessary to ensure the crystallinity of the gallium nitride-based regrowth layer before regrowth of the upper second cladding layer 807 on the stripe groove 820. In the step of holding the wafer at a temperature equal to or higher than 0.degree. C., the n-type GaN material is re-evaporated from the surface or side surface of the current blocking layer 806 around the stripe groove 820, and a part thereof is the first cladding layer 805 at the bottom surface of the stripe groove 820. It turned out to be redeposited on the surface.
[0005]
The above-described problems appear not only in the conventional semiconductor laser, but also in a light emitting diode having a similar current blocking structure, as an increase in the series resistance of the element and a decrease in the current injection region, thereby reducing the yield in element fabrication. It was the cause.
[0006]
[Means for Solving the Problems]
  The present invention covers a first conductivity type first cladding layer, a second conductivity type current blocking layer provided on the first cladding layer and having a removal portion for injecting current, and the removal portion. A gallium nitride-based compound semiconductor light emitting device comprising a first conductivity type second cladding layer provided as described above,A redeposition layer is formed on the bottom surface of the removal portion, and the redeposition layer has the same conductivity type as the first cladding layer,The gallium nitride-based compound semiconductor light emitting device is characterized in that an impurity density of the first cladding layer is set to be larger than an impurity density of the current blocking layer.
[0007]
  The present invention also provides a first conductivity type first cladding layer, a second conductivity type current blocking layer provided on the first cladding layer and having a removal portion for injecting current, and the removal portion. A gallium nitride-based compound semiconductor light-emitting device including a first-conductivity-type second cladding layer provided so as to coverA redeposition layer is formed on the bottom surface of the removal portion, and the redeposition layer has the same conductivity type as the first cladding layer,The gallium nitride-based compound semiconductor light emitting device, wherein the surface layer of the current blocking layer excluding the removal portion contains an impurity having a first conductivity type.
[0008]
  In the gallium nitride compound semiconductor light emitting device according to the present invention, the first cladding layer is formed of Al. _x In _y Ga _z N (x + y + z = 1, 0 ≦ x ≦ 0.1, 0 ≦ y <1, z ≠ 0). Furthermore, the first cladding layer may be made of a material selected so that the amount of evaporation at the crystal growth pretreatment temperature of the second cladding layer is larger than that of the current blocking layer. Further, the current blocking layer is made of Al. _w Ga _1-w N (0 ≦ w ≦ 0.2), and w can be larger than the Al composition of the first cladding layer. Further, the impurity density of the second cladding layer can be equal to or greater than the impurity density of the first cladding layer.
[0009]
  In the gallium nitride-based compound semiconductor light emitting device according to the present invention, the surface layer of the current blocking layer excluding the removal portion may include In.
[0010]
  The present invention also provides a first conductivity type first cladding layer, a second conductivity type current blocking layer provided on the first cladding layer and having a removal portion for injecting current, and the removal portion. A gallium nitride-based compound semiconductor light-emitting device including a first-conductivity-type second cladding layer provided so as to coverA redeposition layer is formed on the bottom surface of the removal portion, and the redeposition layer has the same conductivity type as the first cladding layer,The portion of the first cladding layer facing the removal portion is In_pAl_qGa_1-pqN (0 ≦ p, 0 ≦ q ≦ 0.1, p + q <1).
[0011]
  In the gallium nitride-based compound semiconductor light emitting device according to the present invention, the current blocking layer is made of Al. _w Ga _1-w N (0 ≦ w ≦ 0.2), and w can be larger than the Al composition of the first cladding layer.
[0012]
  The present invention also includes a step of laminating a first conductivity type first cladding layer and a second conductivity type current blocking layer on a substrate, and removing a part of the current blocking layer to remove the first cladding layer. Forming a removal portion while exposingA heat treatment step in which a redeposition layer is formed on the bottom surface of the removed portion;Forming a first conductivity type second cladding layer so as to cover the removed portion.The redeposition layer has the same conductivity type as the first cladding layer.This is a method for manufacturing a gallium nitride-based compound semiconductor light-emitting device.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
FIG. 1 is a schematic diagram of a cross-sectional structure of a gallium nitride based semiconductor laser manufactured in the present embodiment. This gallium nitride based semiconductor laser was manufactured by using ammonia as a group V source, trimethylgallium, trimethylaluminum, trimethylindium as a group III source, and biscyclopentadienyl magnesium (Cp as a p-type impurity).₂Mg), an organic metal compound vapor deposition method (MOCVD method) using monosilane as an n-type impurity and hydrogen and nitrogen as carrier gases. A manufacturing procedure of the element of the present embodiment will be described in detail based on FIG.
[0014]
First, an n-type GaN substrate 101 is introduced onto a susceptor of an MOCVD apparatus, the temperature of the substrate 101 is set to 1000 ° C., and a buffer layer 102 made of n-type GaN is 2 μm thick, n-type Al._0.1Ga_0.9A lower cladding layer 103 made of N is sequentially grown to a thickness of 0.5 μm. Next, the substrate temperature is lowered to 800 ° C. and non-doped In_0.35Ga_0.65An active layer 104 made of N is grown to a thickness of 3 nm. Furthermore, while raising the substrate temperature up to 1000 ° C., Mg is 5 × 10 5.¹⁹cm^-3P-type Al added at a density of_0.1Ga_0.9The upper first cladding layer 105 made of N is 0.25 μm thick, and Mg is 3 × 10¹⁹cm^-3The upper first cladding surface layer 106 made of p-type GaN added at a density of 100 nm thick and Si 5 × 10 5¹⁸cm^-3N-type Al added at a density of_0.15Ga_0.85A current blocking layer 107 made of N is sequentially grown with a thickness of 0.6 μm (FIG. 4A).
[0015]
Next, the wafer is once taken out of the MOCVD growth chamber, and the current blocking layer 107 is removed by etching until the upper first cladding surface layer 106 is exposed using a normal photolithography technique and a dry etching technique. A 1.6 μm stripe groove 120 is formed (FIG. 4B).
[0016]
Next, this wafer is again introduced into the MOCVD apparatus for the second crystal growth. The substrate temperature is raised to 750 ° C. in a mixed gas atmosphere of ammonia, nitrogen, and hydrogen, and in this state, the surface of the upper first cladding surface layer 106 is cleaned for 3 minutes, and then the upper first cladding surface layer 106 and Mg 3 × 10 so as to cover the current blocking layer 107¹⁹cm^-3Al added at a density of_0.1Ga_0.9The upper second cladding layer 108 made of N was regrown with a thickness of 1.2 μm, and the contact layer 109 made of p-type GaN was regrown with a thickness of 0.5 μm. The substrate temperature was gradually raised to 1000 ° C. while performing the second growth. In the following embodiments, the impurity concentration of each layer exposed during regrowth is uniformly distributed in each layer.
[0017]
After completion of the regrowth, the atmosphere was changed to nitrogen gas, and thermal annealing was performed at 800 ° C. for 20 minutes to change the Mg doped layer to p-type, and then the wafer was taken out. Finally, a p-type electrode 110 is formed on the contact layer 109, and an n-type electrode 111 is formed on the substrate 101. Finally, an optical resonator surface was formed by cleavage to obtain a semiconductor laser element (FIG. 4 (3)).
[0018]
In the present embodiment, the current blocking layer 107 is made of 5 × 10 5 of Si indicating n-type as an impurity.¹⁸cm^-3In contrast, the upper first clad surface layer 106 has 3 × 10 Mg, which has p-type impurities as impurities, more than Si.¹⁹cm^-3Included. Thereby, in the cleaning process by heat treatment before regrowth, the crystal material is re-evaporated from the upper first cladding surface layer 106 and the current blocking layer 107, and the redeposition layer 121 formed on the bottom surface of the stripe groove 120 has Mg And Si are contained as impurities, Mg is 2 × 10¹⁹cm^-3, Si is 8 × 10¹⁶cm^-3It was possible to increase the amount of Mg more than 100 times. Therefore, the redeposited layer 121 has a low resistance p-type and does not hinder current injection into the stripe groove 120.
[0019]
Further, in the present embodiment, since the upper first cladding surface layer 106 is made of GaN that does not contain Al, the redeposition layer 121 can be further reduced in resistance. According to the experiments of the present inventor, the material located on the bottom surface of the stripe groove 120 is Al._sGa_1-sWhen N is employed and s ≧ 0.2, the invention tries to solve before the bottom surface of the stripe groove 120 is sufficiently cleaned by re-evaporation of the crystal material in the heat treatment step before regrowth. As explained in the topic, AlO on the surface_xAn oxide film is formed. Of course, such an oxide film increases the resistance of the laser element. However, when s ≦ 0.1, in the heat treatment step before regrowth, Al_sGa_1-sSince N re-evaporates earlier than the formation of the oxide film, such an oxide film is taken into the laser element and does not increase the resistance of the element. As described above, it is desirable that the material located on the bottom surface of the stripe groove 120 has a re-evaporation ability capable of cleaning and removing the oxide film in the heat treatment step before the regrowth. Such materials include the above-mentioned Al._sGa_1-sIn addition to N (s ≦ 0.1), In_pGa_1-pqAl_qN (q ≦ 0.1) was suitable.
[0020]
Further, as described above, the upper first cladding surface layer 106 at the bottom of the stripe groove 120 is made of a material that can remove the oxide film by re-evaporation in the heat treatment step before the regrowth, and the current blocking layer 107 is provided with the upper first cladding surface layer. N-type Al with more Al content than layer 106_0.15Ga_0.85Since N is applied, in the heat treatment step at 750 ° C. in the atmosphere containing ammonia before the regrowth, the amount of reevaporation from the current blocking layer 107 containing more Al is increased by the reevaporation from the upper first cladding surface layer 106. I was able to make it less than the amount. In this way, the thickness of the redeposition layer 121 can be reduced to 3 nm, and the density of Si in the redeposition layer 121 can be reduced. From the difference in impurity density between the upper first cladding surface layer 106 and the current blocking layer 107. However, the difference in impurity density between Mg and Si in the redeposition layer 121 could be increased.
[0021]
Therefore, in the element of the present embodiment, there is no increase in resistance of the element, increase in operating voltage, negative resistance phenomenon, and reduction in element lifetime as seen in the conventional example, and the element resistance is 7.9Ω. An operating current of 5 mW laser beam output was 45 mA, and a device lifetime of 5500 hours was obtained under conditions of 5 mW output in an atmosphere of 60 ° C.
[0022]
Further, the upper first cladding surface layer 106 on the bottom surface of the stripe groove 120 is made of GaN, so that the portion is made of, for example, Al as in the conventional example._0.2Ga_0.8Compared to the case of being formed of N, even when Mg of the same density is added, the generated hole density can be increased by an order of magnitude or more, and the depletion of carriers due to the deterioration of crystallinity at the interface portion. I was able to compensate. This behavior of the hole density is a phenomenon peculiar to the GaN system. By making the upper first cladding surface layer 106 GaN, the hole density near the interface is 10¹⁷cm^-3It was possible to keep the device on the stand, and thus to reduce the series resistance of the device.
[0023]
In order to bring out this cleaning effect, it is desirable that the substrate temperature before the regrowth is 750 ° C. or higher for 1 minute or longer. In addition, when the substrate temperature was set to 1100 ° C. or higher in this heat treatment step, the GaN-based material desorption rate was high and the shape of the stripe groove 120 itself was not maintained. Therefore, the temperature suitable for this heat treatment process was 750 ° C. to 1100 ° C.
[0024]
Further, as described above, the upper second cladding layer 108 is made of 3 × 10 5 of Mg indicating p-type as an impurity.¹⁹cm^-3The density was included. The upper second cladding layer 108 needs to have the same conductivity type as the first cladding layer 105 and the upper first cladding surface layer 106 in order to realize current injection into the stripe groove 120. Furthermore, as a result of examining the density of Mg contained in the upper first cladding surface layer 106 in detail, the density of Mg contained in the second cladding layer 108 is made smaller than the impurity density contained in the upper first cladding surface layer 106. The n-type impurity (Si) contained in the redeposition layer 121 formed in the cleaning process is thermally diffused into the second cladding layer during crystal growth of the second cladding layer, and is formed below the second cladding layer 108. In some cases, an n-type inversion layer appeared. This phenomenon can be prevented by setting the p-type impurity density of the second cladding layer 108 to be equal to or greater than the p-type impurity density of the upper first cladding surface layer 106.
[0025]
(Embodiment 2)
FIG. 2 is a schematic diagram of a cross-sectional structure of another semiconductor laser device manufactured in the present embodiment. The manufacturing procedure of the element of this embodiment will be described in detail with reference to FIG. First, a buffer layer 202 made of GaN, a lower cladding layer 203 made of n-type GaN having a thickness of 2 μm, and an In layer having a thickness of 2 nm are formed on a sapphire substrate 201 by molecular beam epitaxy (MBE)._0.25Ga_0.752 N well layers and 7 nm thick In_0.1Ga_0.9Multiple quantum well active layer 204 composed of three N barrier layers, p-type Al with a thickness of 0.28 μm_0.15Ga_0.85Upper first cladding layer 205 made of N, Mg with an impurity density of 1 × 10¹⁹cm^-3Including 0.1 μm thick p-type In_0.05Ga_0.95Upper first cladding surface layer 206 made of N, Si with an impurity density of 3 × 10¹⁸cm^-3Including 0.3μm thick n-type Al_0.2Ga_0.8A current blocking layer 207 made of N, Zn with an impurity density of 2 × 10¹⁹cm^-3Including 0.1 μm thick p-type In_0.3Ga_0.7The current blocking surface layer 208 made of N is continuously crystal-grown.
[0026]
Next, a stripe groove 220 having a width of 3 μm is formed as a removal region through the current blocking surface layer 208 and the current blocking layer 207 using the normal photolithography technique and the dry etching technique, and the bottom of the wafer is formed. The upper first cladding surface layer 206 is exposed (FIG. 5A).
[0027]
Subsequently, the wafer is placed in an ammonia molecular beam in an MBE apparatus, and the wafer surface is re-evaporated for 10 minutes for cleaning while the temperature is raised to 850 ° C. Thereafter, carbon is continuously doped at 850 ° C. with an impurity density of 4 × 10¹⁸cm^-3Including 1.3 μm thick p-type Al_0.02Ga_0.98Upper second cladding layer 209 made of N, Mg with an impurity density of 1 × 10²⁰cm^-3The contact layer 210 made of p-type GaN is regrown.
[0028]
Also in the case of regrowth by the MBE method, as in the case of the previous embodiment, when the wafer provided with the stripe groove 220 before regrowth is held at a high temperature in an atmosphere containing ammonia, the optimum temperature range is The cleaning (ie, re-evaporation) effect appeared at a temperature higher than 650 ° C., and the shape of the stripe groove 220 on the surface was maintained at 970 ° C. or lower. Further, the holding time before the regrowth requires at least one minute for cleaning the surface as in the MOCVD in the previous embodiment.
[0029]
  Finally, a part of the wafer is etched by a normal photolithography technique and a dry etching technique to expose the lower clad layer 203, and an n-type electrode 211 is formed thereon, and a contact layer210A p-type electrode 212 is formed thereon. In the laser resonator mirror, a vertical surface was simultaneously formed by etching when exposing the lower clad layer 203 to obtain a laser element (FIG. 5B).
[0030]
  In the present embodiment, the wafer was held in an ammonia molecular beam at 850 ° C. for 10 minutes before regrowth. At this time, the current blocking surface layer 208 constituting the wafer surface, the upper first cladding surface layer 206 on the bottom surface of the stripe groove 220, and the current blocking layer 207 exposing the side surface are re-evaporated, and a part of the current blocking surface layer 206 is striped groove.220Redeposition is performed on the bottom surface to form a redeposition layer 221.
[0031]
According to the study by the present inventors, the amount of reevaporation per unit time at a high temperature and the accompanying redeposition amount of the GaN-based semiconductor material are the components mainly contained in the material exposed to the high temperature atmosphere before the regrowth. Then, it turned out that it becomes small in order of InN, GaN, and AlN. That is, in the InGaAlN layer, InN is the most reevaporated and redeposited, and AlN is the least likely. It was found that the reevaporation and redeposition increases as the GaAlN layer contains more Ga.
[0032]
In the present embodiment, the current blocking surface layer 208 occupying the largest surface area is p-type In._0.3Ga_0.7N and the current blocking layer 207 exposed on the side surface of the stripe groove 220 is n-type Al._0.2Ga_0.8N and the upper first cladding surface layer 206 on the bottom surface of the stripe groove 220 is p-type In_0.05Ga_0.95Since the amount of reevaporation and redeposition is N, the current blocking surface layer 208 containing the largest amount of InN is the largest, followed by the upper first cladding surface layer 206, and the smallest is the current blocking layer 207. In fact, little re-evaporation from the current blocking layer 207 was observed (ie, re-evaporation and redeposition of the material containing n-type impurities was suppressed). Therefore, the redeposition layer 221 almost comes from the current blocking surface layer 208 containing the p-type impurity and the upper first cladding surface layer 206. Therefore, it was confirmed that the redeposited layer 221 contains almost no n-type impurities, is composed of InGaN containing Mg and Zn, and is a low-resistance p-type layer. The redeposition layer 221 of this embodiment has a thickness of about 15 nm.
[0033]
In this way, by adding impurities having the same conductivity type to the upper first cladding surface layer 206 and the current blocking surface layer 208 constituting the bottom surface of the stripe groove 220, the conductivity type of the redeposition layer 221 is reliably made p-type. Thus, no negative resistance was observed in the current-voltage characteristics during the operation of the semiconductor laser element, and the series resistance of the element was reduced to 2-7 ohms. As a result, when a laser beam output of several mW was generated, the driving voltage was as low as about 3.9 V, and it was possible to realize a good element having an average life of 7000 hours or more even in a reliability test under high temperature. .
[0034]
Further, in the present embodiment, the current blocking surface layer 208 is changed to In._0.3Ga_0.7N and the current blocking layer 207 as thin as 0.3 μm can absorb the laser light (wavelength 406 nm in the present embodiment) generated in the active layer 204 in the current blocking layer 207, and can absorb the GaN-based semiconductor. The loss guide structure in the laser can be realized. For this reason, the transverse mode of the laser is stable, and it has become possible to operate stably up to a high laser output of 40 mW. Simply using the current blocking layer 207 as an n-type In order to make the current blocking layer 207 have a laser light absorption effect as in the prior art._0.3Ga_0.7In the case of N, re-evaporation and redeposition from the current blocking layer 207 exposed before the regrowth increase, and the redeposition layer 221 becomes n-type or increases in resistance. On the other hand, in the present embodiment, the current blocking layer 207 and the current blocking surface layer 208 having a light absorption effect are configured as described above, so that a laser having a loss guide structure can be realized without such a problem.
[0035]
(Embodiment 3)
FIG. 3 is a schematic diagram of a cross-sectional structure of a gallium nitride light-emitting diode (hereinafter referred to as LED) according to the present embodiment. The LED element includes a p-type SiC substrate 300, a lower cladding layer 301 made of p-type GaN having a thickness of 5 μm, and a p-type Al having a thickness of 0.2 μm._0.2Ga_0.8N confinement layer 302, 0.03 μm thick In_0.2Ga_0.8N active layer 303, 0.2 μm thick n-type Al_0.2Ga_0.8N confinement layer 304, 3 × 10 3 with Si as impurity density¹⁸cm^-3The upper first cladding layer 305 made of n-type GaN having a thickness of 0.15 μm, a 150 μm square removal portion 320 having a width of 1.5 μm, and Mg as an impurity density of 1 × 10¹⁸cm^-3Including a current blocking layer 306 made of p-type GaN having a thickness of 0.6 μm, Si formed so as to cover the current blocking layer 306 and the removal portion 320 as an impurity density of 1 × 10¹⁸cm^-3N-type In having a thickness of 1.0 μm in the removal portion 320 including_0.1Ga_0.9Upper second cladding layer 307 made of N, 1 × 10 5 with Si as impurity density¹⁹cm^-3It includes a contact layer 308 made of n-type GaN having a thickness of 0.3 μm, an n-type electrode 309 formed on the contact layer 308, and a p-type electrode 310 formed on the substrate 300.
[0036]
In the manufacturing process of the LED of this embodiment, the crystal growth is performed by the MOCVD method, and the removal region 320 is taken out from the MOCVD growth chamber when the removal region 320 is formed. Therefore, only the wafer cleaning process before regrowth will be described in detail.
[0037]
A wafer having a 150 μm square removal region 320 formed in the current blocking layer 306 by a normal photolithography technique and etching technique is placed in a MOCVD apparatus in a gas pressure atmosphere of 50 Torr containing approximately equal amounts of ammonia gas and nitrogen gas. In this state, the wafer temperature is raised to 900 ° C., and cleaning is performed by re-evaporation of the wafer surface material and contaminants for about 3 minutes. In this step, the current blocking layer 306 and the upper first cladding layer 305 exposed on the wafer surface are re-evaporated by a thickness of about 5 nm. Part of this re-evaporated material was formed as a redeposition layer 321 with a thickness of about 2 to 6 nm on the bottom surface of the removal region 320 through the gas phase. The thickness was thicker at the periphery of the 150 μm square removal region 320 and thinner at the center.
[0038]
In the present embodiment, since the current blocking layer 306 is p-type and the upper first cladding layer 305 is n-type, the redeposited layer 321 includes both impurities. However, when the upper first cladding layer 305 and the current blocking layer 306 are made of GaN made of the same material, the amount of reevaporation per unit time from each layer is set to be approximately equal, and the upper first cladding layer The n-type impurity density of Si contained in 305 is 3 × 10¹⁸cm^-3The p-type impurity density of Mg contained in the current blocking layer 306 is 1 × 10¹⁸cm^-3By setting it to be larger than that, Si is 2 × 10 as the density of impurities contained in the redeposition layer 321.¹⁸cm^-3, Mg 5 × 10¹⁷cm^-3Thus, it was possible to control to contain more Si, which is an impurity having the same conductivity type as that of the upper first cladding layer 305. Such a layer containing both conductive impurities has an electron density of 1 × 10 5 according to another study result.¹⁸cm^-3It was confirmed to exhibit the n-type.
[0039]
Therefore, the redeposition layer 321 is the same n-type as the upper first cladding layer 305, and the redeposition layer 321 in the LED element effectively suppresses the increase in resistance and the decrease in the light emitting region from the 150 μm square. I was able to. In the element of the present embodiment, the series resistance of the element is 3 to 5 ohms, and a light emission pattern having the same shape (150 μm square) as the formed removal region 320 can be obtained with a high yield.
[0040]
(Embodiment 4)
Next, the semiconductor laser device of this embodiment will be described. FIG. 6 shows a schematic diagram of a cross-sectional structure above the active layer 604 of the element of this embodiment. In this element, Si which is an n-type impurity is formed on the active layer 604 by 1 × 10.¹⁸cm^-3Including 0.2 μm thick n-type Al_0.1Ga_0.9The upper first cladding layer 605 made of N, the stripe groove 620 having a width of 1 μm, and Mg which is a p-type impurity is 3 × 10¹⁹cm^-3Contains p-type Al_0.1Ga_0.9The current blocking layer 606 made of N, the current blocking layer 606 and the stripe groove 620 are formed so as to cover Si.¹⁸cm^-3The upper second cladding layer 607 made of n-type GaN having a thickness of 1.5 μm in the groove 620 including 5 × 10 Si¹⁸cm^-3Including a contact layer 608 made of n-type GaN having a thickness of 0.3 μm, a high concentration region 630 of Si formed in a portion of the upper first cladding layer 605 located on the bottom surface of the stripe groove 620, the high concentration region 630 and the upper second region The redeposition layer 621 is formed between the clad layers 607 and has a thickness of 4 nm.
[0041]
Since the manufacturing procedure of this element is the same as that of the element of the above embodiment, only different portions will be described in detail below. After crystal growth by the first MOCVD method up to the current blocking layer 606, the upper first cladding layer 605 is exposed through the current blocking layer 606 by a normal photolithography technique and a dry etching technique, and the stripe groove 620 is formed. Form. In this state, Si ions are implanted into the entire surface of the wafer using the same mask as the groove 620 formed, so that Si ions are implanted around the bottom surface of the stripe groove 620 (including part of the side surface of the stripe groove 620). To do. The energy of Si ions in this ion implantation was set to 10 keV, and the penetration depth of ions into the crystal was made as shallow as about 0.1 μm. The density of Si atoms implanted into the crystal is 5 × 10¹⁹cm^-3It was controlled to become. In this way, the high concentration region 630 was formed only near the surface of the upper first cladding layer 605.
[0042]
This wafer was heat-treated in an ammonia atmosphere at a temperature of 1050 ° C. for about 10 minutes, both for recovery of ion implantation damage in the high-concentration region 630 and for surface cleaning, before regrowth by the MOCVD apparatus. In this step, the crystal material is re-evaporated from the current blocking layer 606 located on the wafer surface and the high-concentration region 630 of the upper first cladding layer 605, and a redeposition layer 621 is formed. Thereafter, the upper second cladding layer 607 and the contact layer 608 were regrown.
[0043]
In the element manufactured by the above process, in the heat treatment process before regrowth, the material involved in the formation of the redeposition layer 621 is 3 × 10 Mg.¹⁹cm^-3A current blocking layer 606 containing Si and 5 × 10 Si.¹⁹cm^-3A high concentration region 630 is included. In this case, the main material constituting both is Al._0.1Ga_0.9N, and the amount of reevaporation per unit time is the same, but since the high concentration region 630 formed in the upper first cladding layer 605 is larger than the current blocking layer 606, it is the most in the redeposition layer 621. The impurity contained was Si. The amount of impurities contained in the actual redeposition layer 621 is approximately 3 × 10 3 for Si.¹⁹cm^-3And Mg is 3 × 10¹⁸cm^-3It was about.
[0044]
As a result, the redeposition layer 621 in the element of the present embodiment is surely n-type, and the series resistance of the element is as small as about 6 ohms. Moreover, negative resistance could be suppressed efficiently.
[0045]
  (Embodiment 5)
  FIG. 7 is a schematic diagram of a cross-sectional structure of the semiconductor laser device of this embodiment. The element of the present embodiment has the same structure as the element of the second embodiment, but the current of the current blocking layer 207 isPreventionThe main impurity of the surface layer 208 is different only in the technique for increasing the impurity density of the same conductivity type as that of the upper first cladding surface layer 206. In FIG. 7, the same members as those in FIG. 2 are denoted by the same reference numerals, and the impurity concentration is the same unless otherwise specified.
[0046]
In the present embodiment, after the first crystal growth, the wafer is placed in a mixed molecular beam atmosphere of ammonia molecules and Mg molecules that are p-type impurities before the wafer is taken out of the MBE apparatus to form the stripe grooves 220. The wafer was held for 30 minutes while being heated to 800 ° C. As a result, an Mg highly doped layer 731 having a p-type thickness of 0.05 μm was formed on the surface of the current blocking layer 207. In this case, the Mg concentration in the highly Mg-doped layer 731 is 4 × 10.¹⁸cm^-3As a result, the molecular dose of Mg was controlled to be slightly higher than the concentration of Si contained in the current blocking layer 207.
[0047]
As a result, most of the material contributing to the redeposition layer 221 formed on the bottom surface of the stripe groove 220 in the heat treatment step before regrowth becomes the Mg first highly doped layer 731 and the upper first cladding surface layer 206 containing Mg as main impurities. As a result, the main impurity of the redeposition layer 221 can be controlled to Mg. Therefore, the conductivity type of the redeposition layer 221 could be controlled to the same p-type as the upper first cladding layer 205 and the upper first cladding surface layer 206.
[0048]
Therefore, even in the element of the present embodiment, the series resistance of the element can be reduced to 5 to 8 ohms, and the problem of negative resistance can be solved.
[0049]
The present invention is not limited to the above-described various embodiments, and can be applied to all gallium nitride-based light emitting devices manufactured by regrowth on a wafer having a current blocking structure on the surface. Such cases are also included in the scope of the present invention.
(1) The crystal regrowth method is different from the embodiment such as hydride vapor phase growth method.
(2) The case where the laminated structure for blocking current and the shape of the portion through which the current flows are different from those of the embodiment (for example, when the current is blocked at the central portion of the element and flows only at the peripheral portion).
(3) When the materials constituting the element are different gallium nitride systems.
[0050]
【The invention's effect】
According to the present invention, in the gallium nitride compound semiconductor light emitting device having a current blocking structure, the conductivity type of the redeposited layer formed in the heat treatment step before the regrowth is changed to the first cladding layer and the second cladding layer above and below it. It became possible to control to the same conductivity type. As a result, it is possible to effectively suppress the negative resistance and the increase in the series resistance of the element, and as a result, the operating voltage can be reduced and the lifetime of the element can be extended.
[Brief description of the drawings]
1 is a cross-sectional structure diagram of a semiconductor laser according to a first embodiment;
FIG. 2 is a cross-sectional structure diagram of a semiconductor laser according to a second embodiment.
3 is a cross-sectional structure diagram of a light-emitting diode according to Embodiment 3. FIG.
4 is a diagram showing manufacturing steps of the semiconductor laser according to the first embodiment. FIG.
5 is a diagram showing manufacturing steps of the semiconductor laser according to the second embodiment. FIG.
FIG. 6 is a cross-sectional structure diagram of a semiconductor laser according to a fourth embodiment.
7 is a sectional structural view of a semiconductor laser according to a fifth embodiment. FIG.
FIG. 8 is a sectional view of a conventional gallium nitride based semiconductor laser.
[Explanation of symbols]
103, 203, 301 Lower cladding layer
104, 204, 303 active layer
105, 205, 305, 605 Upper first cladding layer
106,206 Upper first cladding surface layer
107, 207, 306, 606 Current blocking layer
208 Current blocking surface layer
108, 209, 307, 607 Upper second cladding layer
630 High concentration region
731 Mg highly doped layer (current blocking surface layer 208)

Claims (10)

A first conductivity type first cladding layer; a second conductivity type current blocking layer provided on the first cladding layer and having a removal portion for injecting current; and the removal portion. A gallium nitride-based compound semiconductor light emitting device comprising a second cladding layer of the first conductivity type,
A redeposition layer is formed on the bottom surface of the removal portion, and the redeposition layer has the same conductivity type as the first cladding layer,
A gallium nitride-based compound semiconductor light-emitting element, wherein an impurity density of a portion of the first cladding layer facing the removal portion is set larger than an impurity density of the current blocking layer. A first conductivity type first cladding layer; a second conductivity type current blocking layer provided on the first cladding layer and having a removal portion for injecting current; and the removal portion. A gallium nitride-based compound semiconductor light emitting device comprising a second cladding layer of the first conductivity type,
A redeposition layer is formed on the bottom surface of the removal portion, and the redeposition layer has the same conductivity type as the first cladding layer,
A gallium nitride-based compound semiconductor light-emitting device, wherein a surface layer of the current blocking layer excluding the removal portion contains an impurity having a first conductivity type. Nitride according to claim 1, characterized in that said first cladding layer is made of _{Al x In y Ga z N (} x + y + z = 1,0 ≦ x ≦ 0.1,0 ≦ y <1, z ≠ 0) Gallium compound semiconductor light emitting device.   4. The nitridation according to claim 3, wherein the first cladding layer is made of a material selected such that the evaporation amount at the crystal growth pretreatment temperature of the second cladding layer is larger than that of the current blocking layer. Gallium compound semiconductor light emitting device. 5. The nitriding according to claim 4, wherein the current blocking layer is made of Al _w Ga _1-w N (0 ≦ w ≦ 0.2), and w is larger than the Al composition of the first cladding layer. Gallium compound semiconductor light emitting device.   2. The gallium nitride-based compound semiconductor light emitting device according to claim 1, wherein an impurity density of the second cladding layer is equal to or greater than an impurity density of the first cladding layer.   The gallium nitride-based compound semiconductor light-emitting element according to claim 2, wherein the surface layer of the current blocking layer excluding the removal portion contains In. A first conductivity type first cladding layer; a second conductivity type current blocking layer provided on the first cladding layer and having a removal portion for injecting current; and the removal portion. A gallium nitride-based compound semiconductor light emitting device comprising a second cladding layer of the first conductivity type,
A redeposition layer is formed on the bottom surface of the removal portion, and the redeposition layer has the same conductivity type as the first cladding layer,
The portion of the first cladding layer facing the removed portion is In _p Al _q Ga _1-pq N (0 ≦ p, 0 ≦ q ≦ 0.1, p + q <1). Compound semiconductor light emitting device. 9. The nitriding according to claim 8, wherein the current blocking layer is made of Al _w Ga _1-w N (0 ≦ w ≦ 0.2), and w is larger than the Al composition of the first cladding layer. Gallium compound semiconductor light emitting device. Laminating a first conductivity type first cladding layer and a second conductivity type current blocking layer on a substrate;
Removing a part of the current blocking layer to expose the first cladding layer and forming a removal portion;
A heat treatment step in which a redeposition layer is formed on the bottom surface of the removal portion;
Forming a second cladding layer of the first conductivity type so as to cover the removal unit, only including,
The method of manufacturing a gallium nitride-based compound semiconductor light-emitting element, wherein the redeposition layer has the same conductivity type as the first cladding layer .

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