JP4940670B2 - Method for fabricating nitride semiconductor light emitting device - Google Patents

Description

  The present invention relates to a method for manufacturing a nitride semiconductor light emitting device.

Patent Document 1 describes a method for manufacturing a semiconductor element. First, a single crystal sapphire substrate treated by organic cleaning and heat treatment is mounted on a susceptor placed in a reaction chamber of a MOVPE apparatus. A buffer layer made of AlN was formed on the main surface (a surface) of the sapphire substrate. Next, an n-type contact layer made of GaN was formed. Thereafter, an n-type cladding layer (low carrier concentration layer) made of non-doped GaN was formed. After forming the n-type cladding layer, an active layer having an MQW structure was formed. The well layer deposition temperature is 730 degrees Celsius, and the barrier layer deposition temperature is 885 degrees Celsius. After raising the temperature of the substrate to 890 degrees Celsius, a p-type cladding layer made of p-type Al _0.15 Ga _0.85 N doped with magnesium (Mg) was formed. The temperature of the substrate was raised to 1000 degrees Celsius to form a p-type contact layer 7 made of Mg-doped p-type GaN. This improves the device performance (input / output level) by lowering the crystal growth temperature of the p-type semiconductor layer than before and avoiding or mitigating physical deterioration of the active layer.
JP 2004-363401 A

When a nitride semiconductor light emitting device is formed on a template on a sapphire substrate, it does not show good device characteristics as expected. According to the inventor's study, this is because an AlGaN layer containing a threading dislocation density of 1 × 10 ⁷ cm ⁻² or more cannot obtain good p-type characteristics.

  In order to suppress degradation of the active layer due to heat, when p-type AlGaN is grown on a base gallium nitride semiconductor having a large threading dislocation density at a temperature of 950 degrees centigrade or less, a (1-10c) plane ( c: a pit composed of a natural number) is formed. When a facet plane such as the (1-10c) plane is formed, the amount of oxygen (O) atoms taken up becomes higher than that of the (0001) plane. Since oxygen atoms act as donors in gallium nitride semiconductors, the introduction of oxygen atoms reduces the hole concentration in the p-type semiconductor layer. As a result, good p-type characteristics cannot be obtained. That is, even if the degradation of the active layer is suppressed, the device performance of the light emitting device is deteriorated because the p-type characteristics are insufficient.

  The present invention has been made in view of such circumstances, and provides a method for manufacturing a nitride semiconductor light-emitting element that can improve the characteristics of a p-type semiconductor layer and suppress deterioration of an active layer. With the goal.

One aspect of the present invention is a method for fabricating a nitride semiconductor light emitting device. In this method, (a) a step of arranging a conductive gallium nitride substrate including a region having a threading dislocation density of 1 × 10 ⁷ cm ⁻² or less in a crystal growth apparatus; and (b) growing the gallium nitride substrate into the crystal. after placement in the _{apparatus, in X Al Y Ga 1-} X-Y N (0.01 ≦ X <1,0 ≦ Y <1) peak wavelength 550nm or less in the wavelength range of 325nm includes a semiconductor layer made of And (c) p-type Al _Z Ga _1-Z N (0 <Z ≦ 1) at a film forming temperature in the range of 800 degrees Celsius or higher and 950 degrees Celsius or lower. Growing a film on the active layer.

According to this method, the deposition temperature of the p-type Al _Z Ga ₁ -ZN film is set in the range of 800 degrees Celsius or higher and 950 degrees Celsius or lower, so that when the p-type Al _Z Ga ₁ -ZN film is grown, Deterioration of the active layer due to heat can be reduced. Also in this case, since a gallium nitride substrate having a threading dislocation density of 1 × 10 ⁷ cm ⁻² or less is used, the p-type Al _Z Ga _1-Z N film grown at the above film formation temperature has a specific facet plane. The density of pits with low is low. Therefore, the oxygen concentration in the p-type Al _Z Ga _1-Z N film can be reduced.

In the method according to the present invention, the p-type Al _Z Ga _1-Z N film may have an oxygen concentration of 7 × 10 ¹⁶ cm ⁻³ or less.

According to this method, since the gallium nitride substrate has a threading dislocation density of 1 × 10 ⁷ cm ⁻² or less, oxygen taken in during the deposition of the p-type Al _Z Ga ₁ -ZN can be reduced. When the dislocation density increases, pits are formed, the oxygen concentration increases, and the p-type semiconductor layer characteristics deteriorate.

  In the method according to the present invention, it is preferable that the temperature of the active layer semiconductor film is in the range of 650 degrees Celsius or higher and 900 degrees Celsius or lower.

According to this _method, the crystal quality of _{In X Al Y Ga 1-X} -Y N (0.01 ≦ X <1,0 ≦ Y <1) active layer including a semiconductor layer made of is improved.

In the method according to the present invention, the threading dislocation density of the p-type _{Al Z Ga 1-Z} N layer can be not more than 1 × ¹⁰ 7 ^{cm -2} or less.

According to this method, it is possible to reduce the p-type _{Al Z Ga 1-Z} N oxygen concentration in the film.

In the method according to the present invention, (d) a p-type Al _U Ga _1- UN (0 ≦ U <Z ≦ 0.25) film is formed at a film forming temperature in a range of 800 degrees Celsius or higher and 950 degrees Celsius or lower. preferably further comprising the step of growing on a p-type _{Al Z Ga 1-Z} N.

  The larger the aluminum composition, the stronger the electron confinement effect, but the higher the specific resistance of the p-type AlGaN layer. By making the p semiconductor layer have a two-layer structure (for example, AlGaN and GaN), it is possible to minimize deterioration of characteristics when the p layer growth temperature is 950 ° C. or lower. When the aluminum composition exceeds 0.25, the characteristics are deteriorated due to other factors than the advantage of the electron confinement effect.

In the method according to the present invention, the p-type _{Al Z Ga 1-Z} N of thickness D (nm) preferably satisfy 5 ≦ D ≦ (-5 × Z + 1.2) × 500.

According to this method, the electron confinement effect becomes a practical level at 5 nanometers or more. when growing the p-type _{Al Z Ga 1-Z} N below 950 degrees Celsius, it is possible to suppress the deterioration of the active layer, in the case of Z = 0 is a p-type GaN film can increased to approximately 600 nm. This is advantageous in that the optical confinement factor can be increased. Thinner thickness of the p-type Al Z _Ga 1-Z _N, the increase in resistance is reduced, it is possible to reduce the increase in the driving voltage of the nitride semiconductor light emitting device.

  The above and other objects, features, and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments of the present invention, which proceeds with reference to the accompanying drawings.

  As described above, according to the present invention, a method for producing a nitride semiconductor light emitting device is provided. According to this method, the characteristics of the p-type semiconductor layer can be improved and the deterioration of the active layer can be suppressed.

  The knowledge of the present invention can be easily understood by considering the following detailed description with reference to the accompanying drawings shown as examples. Subsequently, an embodiment relating to a method for producing a nitride semiconductor light emitting device of the present invention will be described with reference to the accompanying drawings. Where possible, the same parts are denoted by the same reference numerals.

As shown in FIG. 1A, a gallium nitride substrate 11 having a first conductivity type is prepared. This substrate 11 is used to provide a gallium nitride based semiconductor region having a threading dislocation density of 1 × 10 ⁷ cm ⁻² or less. As the substrate 11, for example, an n-type gallium nitride substrate can be used. At least a portion of the gallium nitride substrate is made of a single crystal, the surface of the single crystal portion has a threading dislocation density of 1 × 10 ⁷ cm ⁻² or less, and the entire principal surface 11a of the substrate 11 is 1 It may have a threading dislocation density of × 10 ⁷ cm ⁻² or less.

Subsequently, a gallium nitride based semiconductor is deposited on the substrate 11 having a region for a nitride semiconductor light emitting device having a threading dislocation density of 1 × 10 ⁷ cm ⁻² or less. As a crystal growth apparatus for this deposition, for example, a metal organic vapor phase growth apparatus 10 can be used. For deposition using the metal organic chemical vapor deposition reactor 10, trimethylgallium (TMGa) as a gallium source, trimethylaluminum (TMAl) as an aluminum source, trimethylindium (TMIn) as an indium source, and ammonia (NH ₃ ) as a nitrogen source Silane (SiH ₄ ) can be used as the n-type dopant gas and (CP ₂ Mg) as the p-type dopant gas. In the following description, an n-type gallium nitride substrate having a (0001) plane will be referred to as the substrate 11. This n-type gallium nitride substrate has a threading dislocation density of 1 × 10 ³ cm ⁻² or more and 1 × 10 ⁷ cm ⁻² or less.

Prior to the growth of the gallium nitride based semiconductor, the main surface 11a of the substrate 11 is processed. In this process, after the substrate 11 is disposed on the susceptor 10a of the metal organic chemical vapor deposition furnace 10, the first gas G1 containing NH ₃ and H ₂ is supplied to the metal organic chemical vapor deposition furnace 10, and Is controlled to 101 kPa. The substrate 11 is heat-treated by controlling the furnace temperature to 1050 degrees Celsius. The heat treatment time is, for example, 10 minutes. Thereby, thermal cleaning of the substrate 11 is performed.

As shown in FIG. 1B, an intermediate layer 13 made of a gallium nitride based semiconductor having the first conductivity type is grown on the main surface 11a of the substrate 11. For example, an n-type AlGaN semiconductor is deposited as the intermediate layer 13. The AlGaN semiconductor is grown by supplying a second gas G2 containing TMGa, TMAl, NH ₃ and SiH ₄ to the metal organic chemical vapor deposition reactor 10. The temperature of the metal organic chemical vapor deposition furnace 10 is controlled to 1000 degrees Celsius to 1100 degrees Celsius, and the pressure of the metal organic chemical vapor deposition furnace 10 is controlled to 10 kPa to 101 kPa. The intermediate layer 13 includes a region having a threading dislocation density of 1 × 10 ⁷ cm ⁻² or less. The thickness of the intermediate layer 13 is, for example, 5 nm to 500 nm, and a specific example is 50 nm. An example of the composition is Al _0.12 Ga _0.88 N.

Next, as shown in FIG. 2A, a gallium nitride based semiconductor layer 15 having the first conductivity type is grown on the intermediate layer 13. For example, an n-type GaN semiconductor is deposited as the semiconductor layer 15. The GaN semiconductor is grown by supplying a third gas G3 containing TMGa, NH ₃ and SiH ₄ to the metal organic chemical vapor deposition reactor 10. The furnace temperature is changed to a temperature higher than the growth temperature of the intermediate layer 13, for example. The temperature of the furnace is controlled to 1050 to 1130 degrees Celsius, and the pressure in the furnace is controlled to 10 kPa to 101 kPa. The gallium nitride based semiconductor layer 15 functions as, for example, a buffer layer and a cladding layer. The thickness of the gallium nitride based semiconductor layer 15 is, for example, 0.5 μm to 10 μm, and an example of the thickness is 2 μm. The semiconductor layer 15 includes a region having a threading dislocation density of 1 × 10 ⁷ cm ⁻² or less.

Subsequently, as shown in FIG. 2B, an active layer 17 is grown on the gallium nitride based semiconductor layer 15. The active layer 17 is configured to exhibit an emission spectrum having a peak wavelength in an emission wavelength range of 325 nm or more and 550 nm or less. The furnace temperature is changed to a temperature lower than the growth temperature of the gallium nitride based semiconductor layer 15, for example. For the active layer 17, for example, an In _X Al _Y Ga _1- XYN (0.01 ≦ X <1, 0 ≦ Y <1) semiconductor is deposited. The deposition temperature of the semiconductor film in the active layer 17 is preferably in the range of 650 degrees Celsius or more and 900 degrees Celsius or less. According to this _method, the crystal quality of _{In X Al Y Ga 1-X} -Y N (0.01 ≦ X <1,0 ≦ Y <1) active layer including a semiconductor layer made of is improved. The film formation temperature is preferably 650 ° C. or higher. When the temperature is lower than 650 degrees, an amorphous region is partially formed and works as a defect. However, when the temperature is 650 degrees or more, there is a technical advantage that introduction of these new defects can be suppressed. The film forming temperature is preferably 800 degrees Celsius or less. If the temperature is higher than 800 degrees, the introduction of defects such as N vacancies and In segregation regions is promoted because InAlGaN is easily decomposed. There is a technical advantage that the introduction can be suppressed. The semiconductor film in the active layer 17 is, for example, an InAlGaN semiconductor or an InGaN semiconductor. In the description that follows, an InGaN semiconductor is deposited for the active layer. InGaN is grown by supplying TMGa, TMIn, and NH ₃ to the metal organic vapor phase growth furnace 10. The active layer 17 can have, for example, a quantum well structure. The barrier layer 19a is made of, for example, an In _0.01 Ga _0.99 N semiconductor. The well layer 21a is made of, for example, an In _0.14 Ga _0.86 N semiconductor. In order to grow the barrier layer 19a, the pressure in the metal organic chemical vapor deposition reactor 10 is controlled to 10 kPa to 101 kPa. The thickness of the barrier layer 19a is, for example, 3 nm to 30 nm, and a specific example is 15 nm. For the well layer 21a, the temperature of the metal organic vapor phase growth furnace 10 is controlled to 650 to 800 degrees Celsius, and the pressure in the furnace is controlled to 10 kPa to 101 kPa. The thickness of the well layer 21a is, for example, 1 nm to 6 nm, and a specific example is 3 nm. Subsequently, the growth of the barrier layer and the well layer is repeated alternately until a desired structure is obtained. In this embodiment, the barrier layer 19b, the well layer 21b, and the barrier layer 19c are grown in order. The band gap wavelengths of the barrier layers 19a, 19b and 19c are smaller than the band gap wavelengths of the well layers 21a and 21b.

Subsequently, as shown in FIG. 3A, a p-type Al _Z Ga _1-Z N semiconductor layer 23 is grown on the active layer 17. As the semiconductor layer 23, for example, a p-type AlGaN semiconductor is deposited. The AlGaN semiconductor is grown by supplying a fourth gas G4 containing TMGa, TMAl, NH ₃ and CP ₂ Mg to the metal organic chemical vapor deposition reactor 10. The film forming temperature is preferably 800 degrees Celsius or higher. When the temperature is lower than 800 ° C., the flatness deteriorates, so that the mixing of oxygen is promoted and the specific resistance of the p-type AlGaN semiconductor increases. However, when the temperature is 800 ° C. or higher, good flatness is maintained. In addition, there is a technical advantage that oxygen can be avoided and the specific resistance of the p-type AlGaN semiconductor can be kept low. The film formation temperature is preferably 950 degrees Celsius or less. If the temperature is higher than 950 degrees, there is a problem that the light emission output of the LED is reduced due to the thermal degradation of the active layer, but if it is 950 degrees or less, the thermal degradation of the active layer can be suppressed. Has its own advantages. Moreover, it is preferable that the pressure of the organometallic vapor phase growth furnace 10 is 20 kPa or more. When the pressure is lower than 20 kPa, unintended impurities such as carbon are mixed and the specific resistance is increased. However, when the pressure is 20 kPa or more, it is possible to reduce the adverse effect of these impurities as much as possible. There is. The pressure of the metal organic vapor phase growth furnace 10 is preferably 101 kPa or less. It is possible to suppress the gas phase reaction between TMAl and NH ₃ as much as possible, and there is a technical advantage that the Al composition can be easily increased. The semiconductor layer 23 functions as, for example, a cladding layer. The thickness of the gallium nitride based semiconductor layer 23 is, for example, 5 nm to 50 nm, and a specific example is 20 nm.

Since the deposition temperature of the p-type Al _Z Ga _{1 -Z} N film is set in the range of 800 degrees Celsius or higher and 950 degrees Celsius or lower, the active layer deteriorates due to heat when growing the p-type Al _Z Ga _{1 -Z} N film. Can be suppressed. Also in this case, since a gallium nitride substrate having a threading dislocation density of 1 × 10 ⁷ cm ⁻² or less is used, the oxygen concentration is reduced in the p-type Al _Z Ga ₁ -ZN film grown at the above film formation temperature. it can.

The p-type Al _Z Ga _{1 -Z} N film 23 can include a region having a threading dislocation density of 1 × 10 ⁷ cm ⁻² or less. According to this method, it is possible to reduce the oxygen concentration in the p-type _{Al Z Ga 1-Z} N layer 23.

Further, p-type _{Al Z Ga 1-Z} N layer 23 can have an oxygen concentration of 7 × ¹⁰ 16 ^{cm -3} or less. According to this method, since the gallium nitride substrate has a threading dislocation density of 1 × 10 ⁷ cm ⁻² or less, oxygen taken in during the formation of the p-type Al _Z Ga _1-Z N semiconductor film 23 can be reduced. As the dislocation density increases, pits are formed, the oxygen concentration increases, and the specific resistance of the p-type semiconductor layer increases.

p-type _{Al Z Ga 1-Z} N thickness D of the semiconductor layer 23 (nm) preferably satisfy 5 ≦ D ≦ (-5 × Z + 1.2) × 500. Above 5 nm, the electron confinement effect is at a practical level. The p-type _{Al Z Ga 1-Z} N can suppress the deterioration of the grown active layer 17 below 950 degrees Celsius. In the case of Z = 0 is a p-type _{Al Z Ga 1-Z} N layer can increased to approximately 600 nm, it is advantageous in that the optical confinement coefficient can be increased. If the film thickness of p-type Al Z _Ga 1-Z _N increases, the resistance increases, the driving voltage of the nitride semiconductor light emitting device is increased.

Subsequently, as shown in FIG. 3B, a p-type Al _U Ga _1- UN (0 ≦ U ≦ 0.25) 25 is grown on the p-type Al _Z Ga _1-ZN semiconductor layer 23. To do. For example, a p-type AlGaN semiconductor or a p-type GaN semiconductor is deposited as the semiconductor layer 25. The GaN semiconductor is grown by supplying a fifth gas G5 containing TMGa, NH ₃ and CP ₂ Mg to the metal organic chemical vapor deposition reactor 10. The film forming temperature is preferably 800 degrees Celsius or higher. When the temperature is lower than 800 ° C., the flatness deteriorates, so that the mixing of oxygen is promoted and the specific resistance of the p-type AlGaN semiconductor increases. However, when the temperature is 800 ° C. or higher, good flatness is maintained. In addition, there is a technical advantage that oxygen can be avoided and the specific resistance of the p-type AlGaN semiconductor can be kept low. The film forming temperature is preferably 950 degrees Celsius or less. If the temperature is higher than 950 degrees, there is a problem that the light emission output of the LED is reduced due to the thermal degradation of the active layer, but if it is 950 degrees or less, the thermal degradation of the active layer can be suppressed. Has its own advantages. The pressure in the furnace is preferably 20 kPa or more. When the pressure is lower than 20 kPa, unintended impurities such as carbon are mixed and the specific resistance is increased. However, when the pressure is 20 kPa or more, it is possible to reduce the adverse effect of these impurities as much as possible. There is. The pressure in the furnace is controlled to 101 kPa or less. It is possible to suppress the gas phase reaction between TMAl and NH ₃ as much as possible, and there is a technical advantage that the Al composition can be easily increased. The semiconductor layer 25 functions as a contact layer, for example. The thickness of the semiconductor layer 25 is, for example, 5 nm to 200 nm, and a specific example is 50 nm.

Preferably, the aluminum composition of the p-type Al _Z Ga _1-Z N semiconductor layer 23 is 0 <Z ≦ 0.25, and the aluminum composition of the p _- type Al _U Ga _1- UN semiconductor layer 25 is p-type Al _Z Ga _1-Z N is smaller than the aluminum composition (U <Z). The greater the aluminum composition, the stronger the electron confinement effect of the p-type gallium nitride semiconductor layer, but the higher the specific resistance of the p-type AlGaN layer. By making the p-type semiconductor layer have a two-layer structure of AlGaN and GaN, deterioration of characteristics when the growth temperature of the p-type semiconductor layer is 950 ° C. or lower can be reduced. When the aluminum composition exceeds 0.25, the characteristics are deteriorated due to other factors than the advantage of the electron confinement effect.

Example 1
A blue light emitting diode (LED) was fabricated by metal organic vapor phase epitaxy as follows. As described above, trimethylgallium, trimethylaluminum, trimethylindium, ammonia, silane, and cyclopentadienylmagnesium are used as the film forming material. An n-GaN template (hereinafter referred to as “GaN template substrate”) on a GaN (0001) substrate and a sapphire (0001) substrate is used. The threading dislocation density of the GaN (0001) substrate is 1 × 10 ³ cm ^{−2 to} 1 × 10 ⁷ cm ^{−2 in the} GaN substrate, and the threading dislocation density of the GaN template substrate is 3 × 10 ⁸ cm ^−2. The above is 1 × 10 ¹⁰ cm ⁻² or less. These substrates are placed on a susceptor. While controlling the pressure of the metal organic vapor phase growth furnace to 101 kPa, NH ₃ and H ₂ are supplied into the growth furnace and cleaning is performed at a substrate temperature of 1050 degrees Celsius for 10 minutes. Thereafter, TMG, TMA, NH ₃ , and SiH ₄ are supplied to the metal organic vapor phase growth furnace, and an n-type Al _0.12 Ga _0.88 N intermediate layer having a thickness of 50 nm is grown on both substrates. After raising the substrate temperature to 1100 degrees Celsius, an n-type GaN buffer layer having a thickness of 2000 nm is grown at a growth rate of 2 μm / h. Next, the substrate temperature is lowered to 800 degrees Celsius, and TMG, TMI, and NH ₃ are supplied to the metal organic vapor phase epitaxy furnace, and a 15 nm thick In _0.01 Ga _0.99 N barrier layer, A light emitting layer having a multiple quantum well structure (for example, 6 periods) including a 3 nm In _0.14 Ga _0.86 N well layer is formed.

Thereafter, using various substrate temperatures, a 20 nm thick Mg-doped p-type Al _0.12 Ga _0.88 N layer and a 50 nm thick Mg-doped p-type GaN layer are grown. The magnesium concentration of the p-type AlGaN layer and the p-type GaN layer grown at 1000 degrees Celsius is 6 × 10 ¹⁹ cm ⁻³ , and when the carrier concentration is estimated using hole measurement, 1 to 3 × 10 ¹⁷ cm ^{− 3} hole concentration. Moreover, it is 2 * 10 < ¹⁶ > cm < ^-3 > when oxygen concentration is evaluated using secondary electron emission mass spectrometry.

  After the temperature is lowered to room temperature, these epitaxial substrates are taken out from the growth furnace. A semi-transparent p-electrode is formed on the p-type GaN layer with a metal material, and an n-electrode is formed on the back surface of the n-GaN substrate. In the following description, a blue light-emitting diode manufactured using a GaN (0001) substrate will be referred to as LED1, and a blue light-emitting diode manufactured using a GaN template substrate will be referred to as LED2.

  FIG. 4 is a drawing showing the relationship between the light output of LED 1 and LED 2 and the growth temperature of the p-type semiconductor layer. The abscissa indicates the growth temperature (Celsius) of the p-type semiconductor layer, and the ordinate indicates the light output of LED1 and LED2, and these light outputs are the light output of LED1 and LED2 at 1000 degrees Celsius. Each value is standardized.

As understood from FIG. 4, the light output C1 from the LED 1 (GaN substrate) does not decrease when the growth temperature of the p-type semiconductor layer is in the range of 800 to 950 degrees Celsius. The light output of the LED 1 having a growth temperature of 900 degrees Celsius is the largest. On the other hand, the light output C2 from the LED 2 (sapphire substrate) decreases when the p-type semiconductor layer growth temperature becomes 950 degrees Celsius or lower. Individual data is temperature Standardized light output (LED1) Standardized light output (LED2)
800 degrees Celsius 1.0, 0.4
900 degrees Celsius 1.2, 0.8
950 degrees Celsius 1.1, 1.0
1000 degrees Celsius 1.0, 1.0
1050 degrees Celsius 1.0, 1.0
1100 degrees Celsius 0.9, 0.8
1150 degrees Celsius 0.8, 0.6
It is.

FIG. 5 shows the relationship between the resistivity of the grown p-type semiconductor layer for LED 1 and LED 2 and the growth temperature of the p-type semiconductor layer. The specific resistance C3 of the p-type semiconductor layer (Al _0.12 Ga _0.88 N) of LED1 (GaN substrate) does not depend much on the growth temperature of the p-type semiconductor layer, and is a value of about 2 (Ω · cm). is there. On the other hand, the specific resistance C4 of the p-type semiconductor layer of LED2 (GaN template substrate) increased when the growth temperature of this p-type semiconductor layer was 950 degrees Celsius or less.
Temperature Specific resistance (LED1) Specific resistance (LED2)
800 degrees Celsius 4, 20
900 degrees Celsius 2, 8
950 degrees Celsius 3, 5
1000 degrees Celsius 2, 2
1050 degrees Celsius 2, 2
1100 degrees Celsius 2, 2
1150 degrees Celsius 2, 2
It is.

  From FIG. 4 and FIG. 5, it is considered that the light output of the LED 2 is lowered due to the increase of the specific resistance of the p-type semiconductor layer when the growth temperature of the p-type semiconductor layer is 950 degrees Celsius or less.

FIG. 6 shows a scanning electron microscope image obtained by photographing the surface of the p-type semiconductor layer for the LED 1 (GaN substrate). FIG. 7 shows a scanning electron microscope image obtained by photographing the surface of the p-type semiconductor layer for the LED 2 (GaN template substrate). As shown in FIG. 6, the surface roughness of the p-type semiconductor layer for the LED 1 is small and flat. On the other hand, as shown in FIG. 7, pits composed of the (1-10c) plane are observed on the surface of the p-type semiconductor layer for the LED 2. In the (1-10c) plane, uptake of oxygen (O) atoms increases. Therefore, the average oxygen atom concentration increases to 7 × 10 ¹⁶ cm ⁻³ or more. Further, since oxygen atoms act as donors, it is considered that the specific resistance of the p-type semiconductor layer for the LED 2 increases. Since the threading dislocation density of the p-type semiconductor layer for the LED 1 is 1 × 10 ⁷ cm ⁻² or less, it is estimated that no pits are formed on the surface of the p-type semiconductor layer. From the above, by controlling the threading dislocation density to 1 × 10 ⁷ cm ⁻² or less and growing the p-type semiconductor layer in the range of 800 to 950 degrees Celsius, the thermal degradation of the active layer and the The deterioration of the characteristics of the p-type semiconductor layer grown at the same time can be overcome at the same time, and a light output better than the conventional one can be achieved.

As described above, when a semiconductor light emitting device is manufactured using a conductive gallium nitride substrate having a gallium nitride region having a low threading dislocation density such as a threading dislocation density of 1 × 10 ⁷ cm ⁻² or less, nitridation containing indium is performed. After the active layer including the gallium-based semiconductor layer is formed, the growth temperature of the p-type gallium nitride-based semiconductor layer is in the range of 800 to 950 degrees Celsius, so that the oxygen uptake into the p-type gallium nitride-based semiconductor layer is small. Become. Therefore, the specific resistance of the p-type gallium nitride based semiconductor layer can be reduced. As a result, the light output from the semiconductor light emitting element is improved. On the other hand, when a p-type semiconductor layer is grown at a growth temperature exceeding 950 degrees Celsius using a substrate having a threading dislocation density of 1 × 10 ⁷ cm ⁻² or more, pits composed of (1-10c) planes are generated. The As a result, the oxygen concentration in the p-type semiconductor layer cannot be controlled, and the characteristics of the p-type semiconductor are deteriorated.

  While the principles of the invention have been illustrated and described in the preferred embodiments, it will be appreciated by those skilled in the art that the invention can be modified in arrangement and detail without departing from such principles. The present invention is not limited to the specific configuration disclosed in the present embodiment. We therefore claim all modifications and changes that come within the scope and spirit of the following claims.

FIG. 1A is a drawing showing a step of placing a substrate in a metal organic vapor phase growth furnace. FIG. 1B is a drawing showing a step of growing an intermediate layer on a substrate by metal organic vapor phase epitaxy. FIG. 2A is a diagram illustrating a process of growing a gallium nitride based semiconductor layer on an intermediate layer using a metal organic vapor phase growth furnace. FIG. 2B is a diagram illustrating a process of growing an active layer on a gallium nitride based semiconductor layer by metal organic vapor phase epitaxy. FIG. 3A is a diagram illustrating a process of growing a p-type gallium nitride based semiconductor layer on an active layer using a metal organic vapor phase growth furnace. FIG. 3B is a drawing showing a process of growing another p-type gallium nitride semiconductor layer on the p-type gallium nitride semiconductor layer by metal organic vapor phase epitaxy. FIG. 4 is a drawing showing the relationship between the light output of LED 1 and LED 2 and the growth temperature of the p-layer. FIG. 5 is a graph showing the relationship between the resistivity of the grown p-type semiconductor layer for LED 1 and LED 2 and the growth temperature of the p layer. FIG. 6 is a drawing showing a scanning electron microscope (SEM) image obtained by photographing the surface of the p-type semiconductor layer for the LED 1. FIG. 7 is a drawing showing a scanning electron microscope (SEM) image obtained by photographing the surface of the p-type semiconductor layer for the LED 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Metalorganic vapor phase growth apparatus, 10a ... Susceptor, 11 ... Gallium nitride substrate, 11a ... Substrate main surface, 13 ... Intermediate layer, 15 ... Gallium nitride system semiconductor layer, 17 ... Active layer, 19a, 19b, 19c ... Barrier layers, 21a, 21b ... well layers, 23 ... p-type _{Al Z Ga 1-Z} N semiconductor layer, 25 ... p-type _Al U _{Ga 1-U} N,

Claims (6)

A method for producing a nitride semiconductor light emitting device, comprising:
Disposing a gallium nitride substrate including a region having a threading dislocation density of 1 × 10 ⁷ cm ⁻² or less and exhibiting conductivity in a crystal growth apparatus;
After the gallium nitride substrate is placed in the crystal growth apparatus, the semiconductor layer is made of In _X Al _Y Ga _1- XYN (0.01 ≦ X <1, 0 ≦ Y <1), and is 325 nm or more Forming an active layer exhibiting an emission spectrum having a peak wavelength in a wavelength range of 550 nm or less;
And growing a p-type _{Al Z Ga 1-Z N (} 0 <Z ≦ 1) layer on the active layer at a deposition temperature which is within the range of not less 950 degrees 800 degrees Celsius,
As the contact layer, an Mg-doped p-type Al _U Ga _1- UN (0 ≦ U <Z ≦ 0.25) film at a film forming temperature in the range of 800 ° C. or higher and 950 ° C. or lower is used as the p-type Al. a step of growing on _Z Ga _1-Z N layer,
Forming a p-electrode on the p _- type Al _U Ga _1- UN film;
With
The surface of the p-type Al _U Ga _1- UN film does not include a pit composed of a (1-10c) plane (c is a natural number),
The p-type Al _U Ga _1- UN film has a thickness in the range of 5 nm to 200 nm,
The p-type _{Al Z Ga 1-Z} N layer has an oxygen concentration of 7 × ¹⁰ 16 ^{cm -3} or less, wherein the. The method according to claim 1, wherein the p-type Al _U Ga _1- UN film comprises a single film.   3. The method according to claim 1, wherein a deposition temperature of the semiconductor film of the active layer is in a range of 650 degrees Celsius or more and 900 degrees Celsius or less. 4. The method according to claim 1, wherein a threading dislocation density of the p-type Al _Z Ga _1-Z N film is 1 × 10 ⁷ cm ⁻² or less.   5. The method according to claim 1, further comprising a step of growing an n-type gallium nitride based semiconductor layer on the gallium nitride substrate before growing the active layer. Method. The p-type _{Al Z Ga 1-Z} N layer having a thickness D (unit: nm) satisfies 5 ≦ D ≦ (-5 × Z + 1.2) × 500, that claims 1, wherein Item 6. The method according to any one of Items 5.

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