JP4617922B2 - Manufacturing method of semiconductor device - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming an active layer structure thereof.

  Conventionally, for example, nitride-based III-V compound semiconductors have various wavelength light energies from the ultraviolet region to the red region by changing the composition of this group III element and adjusting the direct band gap energy. Can respond. For this reason, it is generally used as a highly efficient light-emitting element material that can be applied from the ultraviolet region to the visible region.

  By using such a material, for example, a light emitting element having an InGaN-based quantum well structure and corresponding to a relatively short emission wavelength region including an ultraviolet region, a blue region, and the like is manufactured. This light emitting element has a laminated structure of nitride III-V compound semiconductors, and has a structure in which a clad layer having a larger band gap than the laminated structure is formed on both sides of the laminated structure.

  Next, a semiconductor device 78 as an example of a light emitting element (or a light emitting device) having such a structure will be described with reference to FIG.

  According to the AA ′ line cross-sectional view shown in FIG. 8A and the plan view shown in FIG. 8B, the buffer layer 72, the first cladding layer (n-type GaN: Si) 73, An active layer (multi-quantum well: MQW) 75 and a second cladding layer (p-type GaN: Mg) are sequentially stacked. Further, the first cladding layer 73, the active layer 75, and the second cladding layer 76 have a mesa structure, and a part of the first cladding layer 73 is exposed at a halfway position by half-etching. An n-electrode 74 composed of a Ti layer 74a (lower layer) and an Al layer 74b (upper layer) is formed on the region. In addition, a p-electrode 77 composed of a Ni layer 77 a (lower layer) and an Au layer 77 b (upper layer) is formed on the second cladding layer 76.

  FIG. 9 shows in detail the layer configuration of the semiconductor device 78, particularly the active layer 75.

  That is, a barrier layer (GaN) 51, a quantum well layer (InGaN) 52, a barrier layer (GaN) 53, a quantum well layer (on a first cladding layer 73 formed on a substrate 71 with a buffer layer 72 interposed therebetween. InGaN) 54, barrier layer (GaN) 55, quantum well layer (InGaN) 56, and barrier layer (GaN) 57 are appropriate in number (here, the quantum well layer is three layers, but this can be changed arbitrarily) The second cladding layer 76 is laminated on the active layer 75 made of this laminate.

  Next, an example of a manufacturing process of the semiconductor device 78 including the active layer 75 will be described with reference to FIG. 10, which is based on a sequence in which each quantum well layer and each barrier layer are grown at the same temperature.

  First, the sapphire substrate 71 is placed in a metal organic chemical vapor deposition (MOCVD) apparatus and heated (substrate heating) at 1050 ° C. for 10 minutes in an atmosphere made of hydrogen as a carrier gas.

  Next, the temperature is lowered to 500 ° C., and after the supply of ammonia is started, trimethylgallium (TMGa) is supplied to grow a buffer layer (GaN) 72 to a thickness of 30 nm.

  Next, after the supply of trimethylgallium is stopped, the temperature is gradually increased to 1020 ° C., and after reaching 1020 ° C., the supply of trimethylgallium is started again, and the growth of the GaN layer 60 is started.

Next, when the GaN layer 60 is grown to a thickness of 1 μm, supply of monosilane (SiH ₄ ) is started, and the silicon-doped first cladding layer (n-type GaN: Si) 73 is doped at a doping concentration of 2 × 10 ^18. Grow at / cm ³ .

  Next, when the first cladding layer 73 was grown to a thickness of 2 μm, the supply of trimethylgallium and monosilane was stopped, the supply of hydrogen was stopped while the temperature was lowered to 700 ° C., and the carrier gas was changed to nitrogen. Switch. The reason for stopping the supply of hydrogen in this way is to prevent indium in the quantum well layer to be grown next from being etched into the quantum well layer and not being taken into the quantum well layer.

  Next, when the temperature is stabilized at 700 ° C., growth of an active layer (multi-quantum well: MQW) 75 is started.

  That is, the raw materials are triethylgallium (TEGa) and trimethylindium (TMIn), the quantum well layer (InGaN) has a thickness of 1 to 5 nm, for example, 3 nm, and the barrier layer (GaN) has a thickness of 5 to 30 nm, for example, 15 nm. Here, a 3QW structure having three quantum well layers (InGaN) is used. Usually, a 1QW to 10QW structure having 1 to 10 quantum well layers (InGaN) is formed.

  In the growth process of the active layer 75, the supply of triethylgallium is started to grow the barrier layer 51 for facilitating the growth of the quantum well layer 52. After the growth is completed, the supply of trimethylindium is performed. The quantum well layer 52 is grown to start, and further, the supply of trimethylindium is stopped to stop the growth of the quantum well layer 52.

  Next, after the barrier layer 53 is grown, the supply of trimethylindium is started to grow the quantum well layer 54, and then the supply of trimethylindium is stopped to stop the growth of the quantum well layer 54.

  Next, after the barrier layer 55 is grown, the supply of trimethylindium is started to grow the quantum well layer 56, and then the supply of trimethylindium is stopped to stop the growth of the quantum well layer 56. Layer 57 is grown.

After forming the active layer 75 in this manner, the supply of cyclopentadienylmagnesium (Cp ₂ Mg) was started while continuing the supply of triethylgallium while maintaining the temperature at 700 ° C., and the second cladding layer doped with Mg A layer 76a which is a part of (p-type GaN: Mg) 76 is grown to a thickness of 20 nm.

  Thereafter, the supply of triethylgallium and cyclopentadienylmagnesium is interrupted, and while raising the temperature to 950 ° C., the supply of nitrogen is stopped and the carrier gas is switched to hydrogen. By switching to hydrogen in this way, the crystallinity of GaN can be increased.

  Thereafter, supply of trimethylgallium and cyclopentadienylmagnesium is started, and a layer 76b, which is another part of the second cladding layer (p-type GaN: Mg) 76, is grown to a thickness of 200 nm. A part of the p-type GaN: Mg may be p-type AlGaN: Mg.

  After completion of the growth, the temperature is lowered while continuing the supply of ammonia, and the supply of ammonia is stopped at about 300 ° C. Then, the semiconductor device 78 is taken out from the metal organic vapor phase growth apparatus near room temperature.

  The extracted semiconductor device 78 (wafer) is annealed at 800 ° C. for 10 minutes in a nitrogen atmosphere to activate p-type impurities. This is because hydrogen and magnesium (Mg) are not bonded and ionized, so that hydrogen and magnesium are dissociated and ionized.

  Further, a p-electrode 77 composed of a Ni layer 77a / Au layer 77b is formed on the p-type GaN: Mg layer 76 through a lithography process, an etching process, and a vapor deposition process, and the first cladding layer (n-type GaN: On the exposed region of Si) 73, an n-electrode 74 composed of a Ti layer 74a / Al layer 74b is formed.

  As a characteristic of the semiconductor device 78 having such a structure (for example, a light emitting diode LED), a probe is simply probed on a wafer, and a green light emission output is observed with a photodetector disposed under the sapphire substrate 71. Here, each quantum well layer and each barrier layer described above are grown at 700 ° C., but the luminous efficiency at this time is about 30 mW / A (because 0.6 mW is obtained with a drive current of 20 mA). The luminous efficiency is about 30 mW / A).

A structure in which an active layer similar to the active layer is grown is known from Patent Document 1 described later. In addition, a method for preventing the emission wavelength from being shifted to a short wavelength by increasing the growth temperature of the quantum well layer in the active layer as compared with the barrier layer is known in Patent Document 2 described later.
JP 2002-84000 A (page 5 [0016] to page 6 [0019], FIG. 3, FIG. 4, FIG. 7) JP 2003-209285 A (page 3 [0015] to page 4 [0025], page 4 [0030] to page 5 [0034], FIG. 1 and FIG. 2)

  Usually, when a structure composed of multiple quantum well layers is produced by the above-described metal organic chemical vapor deposition (MOCVD), it is common to continuously grow by switching the raw material by switching the valve.

  However, in gallium nitride compound semiconductor devices with a large indium composition ratio, etc., the lattice constant of the GaN layer is mainly different from the lattice constant of the InGaN layer, which is a quantum well layer. It is difficult to grow high-quality crystals. As a result, the light emission efficiency (quantum efficiency) of the green light emitting LED having a large indium composition ratio of the quantum well layer is as low as about half that of the light emission efficiency (quantum efficiency) of the blue light emitting LED. This is because, as described above, the growth temperature of the barrier layer is the same as the growth temperature of the quantum well layer, so that the GaN crystal does not grow sufficiently, and therefore the crystallinity of the quantum well layer also deteriorates. Conceivable. This becomes more remarkable as the indium composition ratio of the quantum well layer increases.

  The present invention has been made in view of such a situation, and its purpose is to increase the luminous efficiency of LEDs, lasers, etc., particularly when growing a quantum well layer having a large indium composition ratio. An object of the present invention is to provide a method for manufacturing a semiconductor device.

  That is, according to the present invention, a multi-layered structure in which a quantum well layer and a barrier layer are stacked has a first cladding layer (for example, n-type GaN: Si) and a second cladding layer (for example, p-type GaN: Mg). ) Between the quantum well layer and the barrier layer so that the temperature is increased after the quantum well layer is grown. The present invention relates to a method for manufacturing a semiconductor device, wherein the barrier layer is grown by raising the barrier layer.

  According to the present invention, the growth temperature of the quantum well layer is different from the growth temperature of the barrier layer, and the barrier layer is grown by increasing the temperature after the growth of the quantum well layer. It is possible to grow a high-quality crystal structure that is sufficiently grown and hardly causes lattice defects. As a result, a quantum well layer having a particularly large indium composition ratio can be grown on this barrier layer with good crystallinity, and the light emission efficiency of a semiconductor device that emits light of a relatively long wavelength such as green can be increased.

  In the present invention, in order to make a crystal structure of good quality without causing lattice defects, the barrier layer is grown by increasing the temperature after the growth of the barrier layer following the growth of the quantum well layer, After the temperature is lowered during the growth of the barrier layer, the quantum well layer can be grown again.

  Further, in order to make a crystal structure with better quality by making lattice defects less likely to occur, after the growth of the quantum well layer, after the growth of the barrier layer, the temperature is increased and the barrier layer is grown. It is desirable to interrupt the growth of the barrier layer and lower the temperature before growing the upper barrier layer and subsequently growing the quantum well layer.

  In order to further increase the quality of the crystal structure by making lattice defects less likely to occur, the growth of the lower barrier layer is continued after the growth of the quantum well layer, the growth is interrupted, and the temperature is increased. It is desirable to grow the barrier layer, then interrupt the growth of the barrier layer, lower the temperature, grow the upper barrier layer, and then grow the quantum well layer.

  In the present invention, the difference between the growth temperature of the barrier layer and the growth temperature of the quantum well layer is 30 ° C. or more, more preferably 50 ° C. or more, in order to make sure that a good quality crystal structure is grown without causing lattice defects. In particular, it is desirable that the temperature be 70 ° C. or higher.

  In this case, the growth temperature is set to 600 ° C. to 800 ° C. (for example, 700 ° C.) in order to make the quantum well layer grow well, and the growth temperature is made to be 630 ° C. to make the barrier layer grow well. It is desirable to set it at 950 ° C. (for example, 770 ° C.).

  In addition, in order to protect the quantum well layer from heat and prevent deterioration of its characteristics, after the formation of the quantum well layer, the lower barrier layer or the barrier layer is grown to a thickness of at least 3 nm. It is desirable to interrupt growth.

  The present invention is suitable for manufacturing a gallium nitride-based compound semiconductor device, and it is particularly preferable to use a mixed crystal material containing indium as the material of the quantum well layer.

  In this case, if the composition ratio of the indium in the quantum well layer is 18% or more, further 23% or more, a light emitting element such as an LED or a laser having an emission wavelength of 480 nm or more, further 500 nm or more can be manufactured. it can.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Example 1

  The light emitting device according to this example has the same structure as that of the conventional example shown in FIGS. 8 to 10 except for the method of forming the active layer. The corresponding part is indicated by a number obtained by subtracting 50 from the number.

  With reference to FIG. 1, a manufacturing process of the light emitting element 28A including the active layer 25 according to the present embodiment will be described.

  First, the sapphire substrate 21 is placed in a metal organic chemical vapor deposition (MOCVD) apparatus and heated (substrate heating) at 1050 ° C. for 10 minutes in an atmosphere made of hydrogen as a carrier gas.

  Next, the temperature is lowered to 500 ° C., and after the supply of ammonia is started, trimethylgallium (TMGa) is supplied to grow the buffer layer (GaN) 22 to a thickness of 30 nm.

  Next, after the supply of trimethylgallium is stopped, the temperature is gradually increased to 1020 ° C., and after reaching 1020 ° C., the supply of trimethylgallium is started again and the growth of the GaN layer 10 is started.

Next, when the GaN layer 10 is grown to a thickness of 1 μm, supply of monosilane (SiH ₄ ) is started, and the silicon-doped first cladding layer (n-type GaN: Si) 23 is doped with a doping concentration of 2 × 10 ^18. Grow at / cm ³ .

  Next, when the first cladding layer 23 is grown to a thickness of 2 μm, the supply of trimethylgallium and monosilane is stopped, the supply of hydrogen is stopped while the temperature is lowered to 700 ° C., and the carrier gas is changed to nitrogen. Switch. The reason for stopping the supply of hydrogen in this way is to prevent indium in the quantum well layer to be grown next from being etched into the quantum well layer and not being taken into the quantum well layer.

  Next, when the temperature is stabilized at 700 ° C., growth of an active layer (multi-quantum well: MQW) 25A is started.

  The raw materials are triethylgallium (TEGa) and trimethylindium (TMIn), and the quantum well layer (InGaN) is laminated to a thickness of 1 to 5 nm, for example, 3 nm, and the barrier layer (GaN) is laminated to a thickness of 5 to 30 nm, for example, 15 nm. However, a 3QW structure having three quantum well layers (InGaN) is used here. Usually, a 1QW to 10QW structure having 1 to 10 quantum well layers (InGaN) is formed.

  In the growth process of the active layer 25A, the supply of triethylgallium is started to grow the barrier layer 1 for facilitating the growth of the quantum well layer 2, and after the growth is completed, the supply of trimethylindium is performed. The quantum well layer 2 is started to grow, and the supply of trimethylindium is stopped to stop the growth of the quantum well layer 2.

  Subsequently, following the growth of the quantum well layer 2, the temperature is increased to 770 ° C. after the growth of the barrier layer 3 is started, the barrier layer 3 is grown to a predetermined thickness, and the temperature is increased to 700 during the growth of the barrier layer 3. After the growth of the barrier layer 3 is finished by lowering to 0 ° C., the supply of trimethylindium is started to grow the quantum well layer 4, and then the supply of trimethylindium is stopped to stop the growth of the quantum well layer 4. .

  Subsequently, following the growth of the quantum well layer 4, the temperature is increased to 770 ° C. after the growth of the barrier layer 5 is started, the barrier layer 5 is grown to a predetermined thickness, and the temperature is increased to 700 ° C. during the growth of the barrier layer 5. After the growth of the barrier layer 5 is finished, the supply of trimethylindium is started to grow the quantum well layer 6, and then the supply of trimethylindium is stopped to stop the growth of the quantum well layer 6.

  Subsequently, following the growth of the quantum well layer 6, the temperature is increased to 770 ° C. after the growth of the barrier layer 7 is started, and after the barrier layer 7 is grown to a predetermined thickness, the growth temperature is maintained at 770 ° C. The growth of the barrier layer 7 is finished.

  In the growth of the barrier layers 3, 5 and 7, a part of the barrier layers 3, 5 and 7 that grow while the growth temperature rises from 700 ° C. to 770 ° C., and the growth temperature falls from 770 ° C. to 700 ° C. Part of the barrier layers 3, 5 and 7 that are grown in the middle are indicated as 3 a, 5 a and 7 a, and 3 b and 5 b, respectively. Since each of these parts has a growth temperature in the range of 700 ° C. to 770 ° C., the crystal to grow does not tend to be uniform or tends to deteriorate. However, since the thickness is small, there is substantially no problem.

After forming the active layer 25A in this manner, the supply of cyclopentadienylmagnesium (Cp ₂ Mg) was started while continuing the supply of triethylgallium while maintaining the temperature at 770 ° C., and the second cladding layer doped with Mg A layer 26a which is a part of (p-type GaN: Mg) 26 is grown to a thickness of 20 nm.

  Thereafter, the supply of triethylgallium and cyclopentadienylmagnesium is interrupted, and while raising the temperature to 950 ° C., the supply of nitrogen is stopped and the carrier gas is switched to hydrogen. By switching to hydrogen in this way, the crystallinity of GaN can be increased.

  Thereafter, supply of trimethylgallium and cyclopentadienylmagnesium is started, and a layer 26b, which is another part of the second cladding layer (p-type GaN: Mg) 26, is grown to a thickness of 200 nm. A part of the p-type GaN: Mg may be p-type AlGaN: Mg.

  After completion of the growth, the temperature is lowered while continuing the supply of ammonia, and the supply of ammonia is stopped at about 300 ° C. Then, the semiconductor device 28A is taken out from the metal organic vapor phase growth apparatus near room temperature.

  The extracted semiconductor device 28A is annealed at 800 ° C. for 10 minutes in a nitrogen atmosphere to activate p-type impurities. This is because hydrogen and magnesium (Mg) are not bonded and ionized, so that hydrogen and magnesium are dissociated and ionized.

  Further, a p-electrode 77 composed of the Ni layer 77a / Au layer 77b shown in FIG. 8 is formed on the p-type GaN: Mg layer 26 through a lithography process, an etching process, and a vapor deposition process, and the first cladding layer. On the exposed region of (n-type GaN: Si) 23, an n-electrode 74 composed of the Ti layer 74a / Al layer 74b shown in FIG. 8 is formed.

  As a characteristic of the semiconductor device 28A having such a structure (for example, a light emitting diode LED), the probe is simply probed on the wafer, and the green light emission output is observed with the photodetector disposed under the sapphire substrate 21.

  According to this example, the growth temperature of each quantum well layer 2, 4 and 6 is 700 ° C., whereas the growth temperature of each barrier layer 3, 5 and 7 is 770 ° C., which is sufficiently high. The growth was continuous. The luminous efficiency at this time was about 70 mW / A. On the other hand, when the growth temperature of each barrier layer 3, 5 and 7 was set to 710 ° C., there was no effect and it remained at about 30 mW / A.

  That is, the growth temperature of each quantum well layer is different from the growth temperature of each barrier layer, and each barrier layer is grown by increasing the temperature after the growth of each quantum well layer. Thus, each barrier layer grows with good crystallinity and its lattice defects are less likely to occur. As a result, each quantum well layer grows with good crystallinity on this barrier layer, and a light emitting element with high luminous efficiency for green light emission having a quantum well layer with a large indium composition ratio can be manufactured.

  FIG. 2 shows the relationship between the luminous efficiency (mW / A) and the growth temperature difference ΔT (° C.) between the barrier layer and the quantum well layer for the light emitting device 28A according to this example. According to this, the light emission efficiency does not change much when the temperature difference ΔT is 0 ° C. to 30 ° C., but the light emission efficiency is increased when the temperature difference ΔT is 30 ° C. or more, and in particular, the temperature difference ΔT is 50 ° C. or more. It can be seen that the luminous efficiency is remarkably improved at 70 ° C. or higher.

Example 2

  In this embodiment, as shown in FIG. 3, after the growth of each quantum well layer, the growth of each barrier layer is started and then the temperature is increased to grow each barrier layer. Example 1 is the same as Example 1 described above except that the growth is interrupted and the temperature is lowered, then each upper barrier layer is grown, and then each quantum well layer is grown.

  That is, the buffer layer 22, the GaN layer 10, and the first cladding layer 23 are sequentially grown on the substrate 21 through the same process as in the first embodiment, and the temperature is lowered to 700 ° C. and stabilized at 700 ° C. The growth of the active layer (multi-quantum well: MQW) 25B is started.

  The raw materials are triethylgallium and trimethylindium, the quantum well layers 2, 4, and 6 have a thickness of 3 nm, the barrier layers 3a and 3A, 5a and 5A, and the thickness of 7 are 14 nm (3 nm or more), and the barrier layers The upper barrier layers 3c and 5c, which are a part, have a thickness of 1 nm.

  Here, the quantum well layer is thermally weak, but the barrier layer is thermally strong. Therefore, in order to protect the quantum well layer by the barrier layer, the thickness of the barrier layer is set to 3 nm or more (14 nm in this example). Is desirable. Also, the presence of the upper barrier layer (GaN) makes it easy to grow the quantum well layer (InGaN) by growing GaN while taking in indium during the growth of the upper barrier layer.

  As a sequence of the growth of the active layer 25B, first, supply of triethylgallium is started, the barrier layer 1 for facilitating the growth of the quantum well layer 2 is grown, and then supply of trimethylindium is started. Then, the quantum well layer 2 is grown, and further, the supply of trimethylindium is stopped to stop the growth of the quantum well layer 2.

  Subsequently, after the growth of the quantum well layer 2, the temperature is increased to 770 ° C. after the growth of the barrier layer 3 is started, the barrier layers 3 a and 3 A are grown, the supply of triethylgallium is stopped, and the barrier layer 3 The growth is interrupted for eg 3 minutes.

  Next, after the temperature is lowered to 700 ° C. during the lapse of the interruption time, the supply of triethylgallium is started and the upper barrier layer 3c which is a part of the barrier layer 3 is grown to a thickness of about 1 nm, and then trimethylindium is grown. Is started to grow the quantum well layer 4, and further, the supply of trimethylindium is stopped to stop the growth of the quantum well layer 4.

  Subsequently, after the growth of the quantum well layer 4, the temperature is increased to 770 ° C. after the growth of the barrier layer 5 is started, the barrier layers 5 a and 5 A are grown, the supply of triethylgallium is stopped, and the barrier layer 5 The growth is interrupted for eg 3 minutes.

  Next, after the temperature is lowered to 700 ° C. during the lapse of this interruption time, the supply of triethylgallium is started and the upper barrier layer 5c which is a part of the barrier layer 5 is grown to a thickness of about 1 nm, and then trimethylindium is grown. Is started to grow the quantum well layer 6, and then the supply of trimethylindium is stopped to stop the growth of the quantum well layer 6.

  Subsequently, following the growth of the quantum well layer 6, the temperature is increased to 770 ° C. after the growth of the barrier layer 7 is started. After the barrier layers 7 a and 7 are grown, the barrier layer is maintained at the growth temperature of 770 ° C. End the growth of 7.

  In the growth of the barrier layers 3, 5 and 7, portions of the barrier layers 3, 5 and 7 which are grown while the growth temperature is raised to 700 ° C. to 770 ° C. are shown as 3a, 5a and 7a, respectively. Since each of these parts has a growth temperature of 700 ° C. to 770 ° C., crystal growth may not be uniform, but there is substantially no problem.

  In the subsequent manufacturing steps, the second cladding layer (p-type GaN: Mg) 26, the p-electrode 77, and the n-electrode 74 are sequentially formed in the same manner as in Example 1 described above, thereby completing the manufacture of the light-emitting element 28B. .

  According to this example, the growth temperature of each quantum well layer 2, 4, 6 is 700 ° C., whereas the growth temperature of each barrier layer 3A, 5A, 7 is sufficiently high at 770 ° C. As described in Example 1 above, each barrier layer hardly causes lattice defects and improves crystallinity.

  Moreover, during the growth of each barrier layer, the growth is temporarily interrupted, and during this time, the growth temperature is lowered, and then the barrier layers 3c and 5c (thickness of about 1 nm) are grown, on which the quantum well layer 4 6 is grown, the barrier layer growth is interrupted during the above-described temperature drop, so that the barrier layer having poor crystallinity that grows unevenly or grows at a low temperature can be reduced as much as possible. it can. As a result, a light emitting device having a green light emission efficiency of about 125 mW / A could be obtained.

  FIG. 4 shows a comparison between the X-ray diffraction spectrum (XRD) of the light-emitting element 78 according to the conventional example and the X-ray diffraction spectrum of the light-emitting element 28B according to this example.

  As shown in FIG. 4A, in the light emitting element 78 according to the conventional example manufactured in the sequence shown in FIG. 10, a shoulder (sub peak) is generated at the peak of the GaN layer, and the satellite peak is also broad.

  Such a bad result is mainly because the growth temperature of each barrier layer is the same (700 ° C.) as the growth temperature of each quantum well layer, so that each InGaN layer (quantum well layer) and each GaN layer (barrier layer). It is considered that the lattice mismatch is caused and the crystallinity of each barrier layer is poor and lattice defects are easily generated, which adversely affects each quantum well layer.

  On the other hand, as shown in FIG. 4B, in the light emitting device 28B according to this example, the peak of the GaN layer is a clean single peak, and the satellite peak is also narrow.

  Such a good result is mainly due to the fact that the growth temperature of each barrier layer (770 ° C.) is sufficiently higher than the growth temperature of each quantum well layer (700 ° C.). This is probably because the crystallinity of each barrier layer is good and lattice defects are less likely to occur, which has a positive effect on each quantum well layer.

  FIG. 5 shows the correlation between PL (photoluminescence) emission wavelength (nm) and PL emission intensity (arbitrary value) and the GaN thickness (nm) from QW to the barrier layer growth interruption interface. According to this, when the GaN thickness from the QW to the growth interruption interface is less than 3 nm, the underlying InGaN layer may be damaged because it is thin, and the PL emission wavelength is 500 nm or less, and the wavelength shortening is remarkable. Since the PL emission intensity is also as low as 0.8 (arbitrary value) or less, it is understood that the GaN thickness is preferably 3 nm or more, and particularly preferably 6 nm or more.

  That is, if the GaN layer thickness before the growth interruption is less than 3 nm, a noticeable shortening of the wavelength and a decrease in the strength occur, and this is because the InGaN layer is not protected during the interruption of the growth of the GaN layer. This is thought to be because deterioration (defects) in the quantum well layer occurs.

  When the GaN thickness from the InGaN layer (QW) to the GaN layer growth interruption interface is 3 nm or more (especially 6 nm or more), the PL emission wavelength is 500 nm or more (particularly 510 nm or more), and the PL emission intensity is 0.8 ( In particular, near 1.0), it is possible to realize a longer emission wavelength and an increase in emission intensity.

  With regard to the improvement of the light emission efficiency together with these effects, a light emitting element with a light emission wavelength of 430 nm or less with a small In composition ratio has little effect, and the light emission wavelength (nm) and EL (electroluminescence) efficiency shown in FIG. According to the correlation with A), the EL efficiency according to this example is higher than that of the conventional example at an emission wavelength of 480 nm (corresponding to In18%) or more, particularly 500 nm (corresponding to In23%) or more with an increased In composition ratio. It turns out that it becomes twice or more. Further, the EL efficiency at the emission wavelength of 520 nm according to Example 1 described above is improved more than twice as compared with the conventional example, and the effect of improving the efficiency is great.

  In addition, in this embodiment, the same operations and effects as described in the first embodiment can be obtained.

Example 3

  In this example, as shown in FIG. 7, following the growth of each quantum well layer, the growth of each lower barrier layer is interrupted and then the growth is interrupted. Other than growing the barrier layers, further interrupting the growth of these barrier layers, lowering the temperature during this interruption, then growing each upper barrier layer, followed by each quantum well layer, It is the same as that of Example 1 mentioned above.

  That is, the buffer layer 22, the GaN layer 10, and the first cladding layer 23 are sequentially grown on the substrate 21 through the same process as in the first embodiment, and the temperature is lowered to 700 ° C. and stabilized at 700 ° C. The growth of the active layer (multi-quantum well: MQW) 25C is started.

  The raw materials are triethylgallium and trimethylindium, the quantum well layers 2, 4, and 6 have a thickness of 3 nm, the barrier layers 3A, 5A, 7a, and 7 have a thickness of 14 nm (3 nm or more). The upper barrier layers 3c and 5c have a thickness of 1 nm, and the lower barrier layers 3d and 5d, which are part of the barrier layer, have a thickness of 3 nm.

  Here, although the quantum well layer is thermally weak, the barrier layer is thermally strong. Therefore, it is desirable to protect the quantum well layer by the lower barrier layer. Further, indium is taken in during the growth of the upper barrier layer to grow the quantum well layer.

  As a growth sequence of the active layer 25C, first, supply of triethylgallium is started at 700 ° C., the barrier layer 1 for facilitating the growth of the quantum well layer 2 is grown, and then supply of trimethylindium is performed. Is started to grow the quantum well layer 2, and the supply of trimethylindium is stopped to stop the growth of the quantum well layer 2.

  Subsequently, after the growth of the quantum well layer 2, the lower barrier layer 3d is grown, and then the supply of triethylgallium is stopped and the growth of the barrier layer 3 is interrupted for 3 minutes, for example.

  Next, after the temperature is raised to 770 ° C. during this interruption, the supply of triethylgallium is started to grow the barrier layer 3A, and then the supply of triethylgallium is stopped to grow the barrier layer 3 to, for example, 3 Break for a minute.

  Next, after the temperature is lowered to 700 ° C. during the interruption, the supply of triethylgallium is started to grow the upper barrier layer 3c, and then the supply of triethylgallium is stopped to grow the upper barrier layer 3c. Stop.

  Next, the supply of trimethylindium is started to grow the quantum well layer 4, and then the supply of trimethylindium is stopped to stop the growth of the quantum well layer 4.

  Subsequently, after the growth of the quantum well layer 4, the lower barrier layer 5 d is grown, and then the supply of triethylgallium is stopped and the growth of the barrier layer 5 is interrupted for 3 minutes, for example.

  Next, after the temperature is raised to 770 ° C. during this interruption, the supply of triethylgallium is started to grow the barrier layer 5A, and then the supply of triethylgallium is stopped to grow the barrier layer 5 to, for example, 3 Break for a minute.

  Next, after the temperature is lowered to 700 ° C. during this interruption, the supply of triethylgallium is started to grow the upper barrier layer 5 c, and then the supply of trimethylindium is started to grow the quantum well layer 6. Then, the supply of trimethylindium is stopped and the growth of the quantum well layer 6 is stopped.

  Subsequently, following the growth of the quantum well layer 6, the temperature is increased to 770 ° C. after the growth of the barrier layer 7 is started. After the barrier layers 7 a and 7 are grown, the barrier layer is maintained at the growth temperature of 770 ° C. End the growth of 7.

  In the subsequent manufacturing steps, the second cladding layer (p-type GaN: Mg) 26, the p-electrode 77, and the n-electrode 74 are sequentially formed in the same manner as in Example 1 described above, thereby completing the manufacturing of the light-emitting element 28C. .

  According to this example, the growth temperature of each quantum well layer 2, 4, 6 is 700 ° C., whereas the growth temperature of each barrier layer 3A, 5A, 7 is sufficiently high, 770 ° C. As described in the first embodiment, each barrier layer grows with good crystallinity.

  In addition, the growth of each lower barrier layer and each barrier layer is temporarily interrupted during the growth, and the growth temperature is lowered or raised during this time, and then the upper barrier layer and the barrier layer are grown. By interrupting the growth of the barrier layer or the lower barrier layer during the warm period, a part of the barrier layer having poor crystallinity that grows unevenly or grows at a low temperature (ie, the upper barrier layer and the lower barrier layer) is removed. As little as possible. As a result, the green luminous efficiency was about 130 mW / A equivalent to that in Example 2.

  Further, as in the second embodiment described above, the thickness of the lower barrier layer is preferably 3 nm or more in order to protect the quantum well layer from damage.

  In addition, in this embodiment, the same operations and effects as described in the first embodiment can be obtained.

  As mentioned above, although this invention was demonstrated based on embodiment and an Example, it cannot be overemphasized that these examples can be suitably changed in the range which does not deviate from the main point of this invention.

  For example, the above-described growth conditions for each layer, the constituent materials used, and the like may be variously changed. In FIG. 7 described above, as indicated by a broken line, the temperature may be raised from the beginning of the growth of the lower barrier layer, but in this case, the crystallinity of the lower barrier layer is improved. Note that the present invention can also be applied to a semiconductor device using another material having a quantum well layer having a large lattice mismatch in addition to the above-described materials.

  The method for manufacturing a semiconductor device according to the present invention is suitable for manufacturing a light emitting diode, a laser and the like for light emission with a long wavelength emission with improved luminous efficiency.

It is a flowchart which shows the manufacturing process of the light emitting element by Example 1 of this invention. It is a graph which shows the correlation with luminous efficiency and the growth temperature difference of a barrier layer and a quantum well layer. It is a flowchart which shows the manufacturing process of the light emitting element by Example 2 of this invention. 3 is a graph showing comparison of X-ray diffraction spectra of GaN layers. 3 is a graph showing the correlation between the PL emission wavelength and the PL emission intensity and the GaN thickness from the QW to the growth interruption interface. 3 is a graph showing the correlation between EL efficiency and emission wavelength. It is a flowchart which shows the manufacturing process of the light emitting element by Example 3 of this invention. It is sectional drawing (A) and the top view (B) of the light emitting element by a prior art example. FIG. 3 is a partial detailed cross-sectional view of the light emitting element. 4 is a flowchart showing a manufacturing process of the light emitting element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Barrier layer, 2 ... Quantum well layer, 3 ... Barrier layer, 3a, 3b ... A part of barrier layer,
3c ... Upper barrier layer, 3d ... Lower barrier layer, 4 ... Quantum well layer, 5 ... Barrier layer,
5a, 5b ... part of the barrier layer, 5c ... upper barrier layer, 5d ... lower barrier layer,
6 ... quantum well layer, 7 ... barrier layer, 7a ... part of barrier layer, 10 ... GaN layer, 21 ... substrate,
22 ... buffer layer, 23 ... first cladding layer, 25A, 25B, 25C ... active layer,
26 ... second cladding layer, 26a, 26b ... part of the second cladding layer,
28A, 28B, 28C ... Light emitting element

Claims (9)

Upon manufacturing a semiconductor device to place across the multiple layered structure formed by laminating a quantum well layer and a barrier layer between the first cladding layer and the second cladding layer, and the growth temperature of the quantum well layer A method for manufacturing a semiconductor device, wherein a growth temperature of the barrier layer is different, and the barrier layer is grown by increasing the temperature after the growth of the quantum well layer ,
Subsequent to the growth of the quantum well layer composed of the first and second group III elements and the group V element which are different from each other , the temperature after the start of the growth of the barrier layer composed of the second group III element and the group V element. from grown the barrier layer is raised to interrupt the growth of the barrier layer, after lowering the temperature, to grow a top barrier layer of the barrier layer and the same composition, followed by pre-Symbol quantum well layer Grow,
A method for manufacturing a semiconductor device . Subsequent to the growth of the quantum well layer, a lower barrier layer having the same composition as that of the barrier layer is grown, the growth is interrupted, the temperature is increased, and then the barrier layer is grown. The method for manufacturing a semiconductor device according to claim 1, wherein the growth is interrupted and the temperature is lowered, and then the upper barrier layer is grown, and then the quantum well layer is grown.   The method of manufacturing a semiconductor device according to claim 1, wherein a difference between a growth temperature of the barrier layer and a growth temperature of the quantum well layer is set to 30 ° C. or more. 4. The method of manufacturing a semiconductor device according to claim 3 , wherein a growth temperature of the quantum well layer is 600 ° C. to 800 ° C., and a growth temperature of the barrier layer is 630 ° C. to 950 ° C. 5. Wherein after formation of the quantum well layer, interrupting its growth after said lower barrier layer or the barrier layer is grown to a thickness of at least 3 nm, a manufacturing method of a semiconductor device according to claim 1 or 2.   The method for manufacturing a semiconductor device according to claim 1, wherein a gallium nitride compound semiconductor element is manufactured. An InGaN the material of the quantum well layer, Ru using GaN as the material of the barrier layer, a method of manufacturing a semiconductor device according to claim 6. The method for manufacturing a semiconductor device according to claim 7 , wherein a composition ratio of the indium in the quantum well layer is 18% or more. The method for manufacturing a semiconductor device according to claim 8 , wherein a light emitting element having an emission wavelength of 480 nm or more is manufactured.

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