JP4823698B2 - Nitride semiconductor device manufacturing method - Google Patents

Description

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

  As a semiconductor light emitting element such as a semiconductor laser element or a light emitting diode emitting blue or violet light, there is a gallium nitride semiconductor light emitting element. When manufacturing a GaN-based semiconductor element, it is difficult to manufacture a substrate made of GaN. Therefore, a GaN-based semiconductor layer is epitaxially grown on a substrate made of sapphire, SiC, Si, or the like.

For example, using MOCVD (metal organic chemical vapor deposition) on the (0001) surface of a sapphire substrate, a GaN low-temperature buffer layer, an n-GaN contact layer, an n-AlGaN cladding layer, an n-GaN light guide layer, an InGaN multiple layer A quantum well (MQW) active layer and the like are sequentially formed, and a p-AlGaN layer, a p-GaN contact layer, and the like are sequentially formed on the active layer (see, for example, Patent Document 1).
JP 2001-77416 A

  However, since the formation conditions of the p-AlGaN layer and the p-GaN layer are usually greatly different, after forming the p-AlGaN layer, it is necessary to interrupt the film formation and switch the formation conditions. At this time, if Al is present on the surface, Al is combined with O or C, which is a factor that hinders light emission.

  In view of the above problems, an object of the present invention is to provide a method for manufacturing a nitride-based semiconductor element that suppresses a decrease in luminous efficiency due to Al bonding.

In order to achieve the above object, the present invention is characterized in that at least one nitride-based semiconductor layer is formed on a substrate, and an active layer is formed on the nitride-based semiconductor layer. A step of supplying Al and forming an AlGaN layer on the active layer using a carrier gas composed of H ₂ and N _{2 under a} condition that the flow rate of N ₂ is larger than H ₂ in the carrier gas ; On top of this, the step of forming only the first GaN layer by stopping the supply of Al under the same conditions as those for forming the AlGaN layer, and using a carrier gas composed of H ₂ and N _{2 in the} carrier gas The present invention is summarized as a method for manufacturing a nitride-based semiconductor device including a step of forming a second GaN layer on the first GaN layer under a condition that the flow rate of N ₂ is smaller than H ₂ .

  According to the method for manufacturing a nitride-based semiconductor device according to the features of the present invention, only the supply of Al is stopped under the same conditions as for the AlGaN layer, and the surface layer is covered with the first GaN layer, thereby emitting light by bonding of Al. A decrease in efficiency can be suppressed.

In the method for manufacturing a nitride-based semiconductor device according to the feature of the present invention, the nitrogen component of the nitride-based semiconductor is included under the same conditions as those for forming the AlGaN layer in the step of forming the first GaN layer. The flow rate ratio of the raw material gas to be contained and H ₂ and N ₂ may be included .

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the nitride-type semiconductor element which suppresses the fall of the luminous efficiency by the coupling | bonding of Al can be provided.

  Next, embodiments of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions and the like are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(Nitride light emitting diode device manufacturing method)
FIG. 1 is a cross-sectional view for explaining a method for manufacturing a nitride-based light emitting diode device according to an embodiment of the present invention. FIG. 2 shows the transition of the growth temperature in the method for manufacturing a nitride-based light emitting diode device according to the embodiment of the present invention, and FIG. 3 shows the supply amount of each raw material in the stage A of FIG. .

  First, as shown in FIG. 1A, an n-type semiconductor layer 102, an active layer 103, and a p-type AlGaN layer 104 are formed on a sapphire substrate 101 using a MOCVD (Metal Organic Chemical Vapor Deposition) method.

For example, in a state where the sapphire substrate 101 is held at a temperature of about 400 to 700 ° C., a source gas composed of NH ₃ and TMG (trimethylgallium) is used to form an undoped non-single layer on the (0001) surface of the sapphire substrate 101. A buffer layer made of crystalline GaN is grown.

Next, in a state where the sapphire substrate 101 is maintained at a growth temperature of about 900 to 1200 ° C. (for example, 1050 ° C.), an undoped single crystal GaN is formed on the buffer layer using a source gas composed of NH ₃ and TMG. A base layer made of is grown.

Next, in a state where the sapphire substrate 101 is held at a growth temperature of about 900 to 1200 ° C. (for example, 1050 ° C.), a base layer is formed using a source gas composed of NH ₃ and TMG and a dopant gas composed of SiH _4. An n-type contact layer made of single-crystal GaN doped with Si is grown thereon.

Next, in a state where the sapphire substrate 101 is maintained at a growth temperature of about 900 to 1200 ° C. (for example, 1050 ° C.), a source gas composed of NH ₃ , TMG and TMA (trimethylaluminum), a dopant gas composed of SiH ₄ , Then, an n-type cladding layer made of single-crystal AlGaN doped with Si is grown on the n-type contact layer.

  As described above, the n-type semiconductor layer 102 includes a buffer layer, a base layer, an n-type contact layer, an n-type cladding layer, and the like. The thickness of the n-type semiconductor layer 102 is preferably about 5 μm.

Next, in a state where the sapphire substrate 101 is held at a growth temperature of about 700 to 800 ° C. (for example, 760 ° C.), a source gas made of NH ₃ , TMG, or TMI (trimethylindium) is used to form the n-type semiconductor layer 102. On top, a barrier layer made of undoped single crystal GaN or InGaN and a well layer made of undoped single crystal InGaN are grown alternately. Thereby, for example, an active layer 103 having an MQW structure having four barrier layers and three well layers is grown (201 in FIG. 3). The thickness of the active layer 103 is preferably about 0.1 to 0.2 μm.

Next, with the sapphire substrate 101 held at a growth temperature of about 900 to 1200 ° C. (for example, 1010 ° C.), a carrier gas composed of H ₂ and N ₂ , a source gas composed of NH ₃ , TMG and TMA, A p-type AlGaN layer 104 made of single-crystal AlGaN doped with Mg is grown on the active layer 103 using a dopant gas made of CP ₂ Mg (202 portion in FIG. 3). At this time, the flow rate ratio of each gas is about H ₂ : N ₂ : NH ₃ = 4: 30: 4, the flow rate of TMG is about 3.83 × 10 ⁻⁵ mol / min, and the flow rate of TMA is It is preferably about 1.72 × 10 ⁻⁶ mol / min. Further, the growth time of the p-type AlGaN layer 104 is preferably about 4 to 8 minutes. The thickness of the p-type AlGaN layer 104 is preferably about 0.2 μm.

  Next, as shown in FIG. 1B, a first p-type GaN layer 105 is formed on the p-type AlGaN layer 104 by using a MOCVD (Metal Organic Chemical Vapor Deposition) method.

For example, with the sapphire substrate 101 held at a growth temperature of about 900 to 1200 ° C. (eg, 1010 ° C.), a carrier gas composed of H ₂ and N ₂ , a source gas composed of NH ₃ and TMG, and CP ₂ Mg The first p-type GaN layer 105 is grown on the p-type AlGaN layer 104 using a dopant gas made of (203 in FIG. 3). The formation conditions of the first p-type GaN layer 105 are the same as the formation conditions of the p-type AlGaN layer 104 except that the supply of TMA is stopped. Therefore, the flow rate ratio of each gas is preferably about H ₂ : N ₂ : NH ₃ = 4: 30: 4, and the flow rate of TMG is preferably about 3.83 × 10 ⁻⁵ mol / min. Further, the growth time of the first p-type GaN layer 105 is preferably about 1 minute. The thickness of the first p-type GaN layer 105 is preferably about 0.001 to 0.05 μm, and more preferably about 0.05 μm.

  Next, as shown in FIG. 1C, a second p-type GaN layer 106 is formed on the first p-type GaN layer 105 by using a MOCVD (Metal Organic Chemical Vapor Deposition) method.

For example, in a state where the sapphire substrate 101 is held at a growth temperature of about 900 to 1200 ° C. (for example, 1010 ° C.), a carrier gas composed of H ₂ and N ₂ and a source gas composed of NH ₃ and TMG are used. A second p-type GaN layer 106 is grown on the first p-type GaN layer 105 (204 portion in FIG. 3). At this time, the flow rate ratio of each gas is preferably about H ₂ : N ₂ : NH ₃ = 4: 1: 2, and the flow rate of TMG is preferably about 8.93 × 10 ⁻⁵ mol / min. The growth time of the second p-type GaN layer 106 is preferably about 6 minutes. The thickness of the second p-type GaN layer 106 is preferably about 0.05 to 0.2 μm, and more preferably about 0.1 μm.

  Thereafter, for example, a p-type electrode composed of an Ag layer, a Pt layer, and an Au layer is sequentially formed by a vacuum deposition method.

(Function and effect)
Conventionally, since the formation conditions of the p-type AlGaN layer 104 are different from the formation conditions of the p-type GaN layer, after the p-type AlGaN layer 104 is formed, the film formation is once interrupted and the formation conditions are switched. At this time, if Al is present on the surface, Al and impurities such as O and C are combined to cause light emission.

  According to the method for manufacturing a nitride-based semiconductor device according to the present embodiment, only the supply of Al is stopped under the same conditions as the p-type AlGaN layer 104, and the surface layer is covered with the first p-type GaN layer 105. A decrease in light emission efficiency due to bonding of Al can be suppressed.

  This is also effective because it is confirmed that the recombination of the active layer 103 can be suppressed by inserting an AlGaN electron blocking layer under the p-type GaN layer by simulation from a band diagram in an InGaN-based LED. There is expected.

  The first p-type GaN layer 105 is different from the p-type AlGaN layer 104 only in the supply of Al, and other formation conditions (growth temperature, flow rate of each gas, etc.) are all the same. Therefore, the first p-type GaN layer 105 can be formed continuously without interruption after the p-type AlGaN layer 104 is formed. Therefore, even if Al is present on the surface of the p-type AlGaN layer 104, the possibility of bonding with O or C is low.

  Further, since the first p-type GaN layer 105 is grown under the growth conditions of the p-type AlGaN layer 104, the characteristics are worse than those of the second p-type GaN layer 106. For this reason, the film thickness of the first p-type GaN layer 105 is preferably as thin as 0.001 to 0.05 μm.

(Other embodiments)
Although the present invention has been described according to the above-described embodiments, it should not be understood that the descriptions and drawings constituting a part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art.

  For example, in the embodiment of the present invention, the method of manufacturing a light emitting diode that mainly uses light emitted from the active layer of the nitride semiconductor element layer is exemplified. However, the present invention is not limited to this, and the present invention is not limited thereto. The present invention can also be used for manufacturing a light-emitting element that combines a phosphor that uses light emitted from the light-emitting element as excitation light. Further, it can be applied to electronic devices such as HEMT (High Electron Mobility Transistor) having a nitride-based semiconductor element layer, SAW (Surface Acoustic Wave) devices, and light receiving elements.

  In the embodiments of the present invention, the MOCVD method is used to describe the crystal growth of each nitride semiconductor layer. However, the present invention is not limited to this, and the HVPE method, the gas source MBE method, etc. Each semiconductor layer may be crystal-grown. The crystal structure of the nitride compound semiconductor may be a wurtzite type or a zinc blende type structure. Further, the growth plane orientation is not limited to (0001), and may be (11-20) or (1-100).

  In the embodiment of the present invention, a nitride-based semiconductor element layer including a layer made of GaN, AlGaN, InGaN, AlN, or the like is used. However, the present invention is not limited to this, and GaN, AlGaN, InGaN, and AlN A nitride-based semiconductor element layer including a layer other than the layer to be formed may be used. The semiconductor element layer may have a current confinement structure such as a mesa structure or a ridge structure.

  In the embodiment of the present invention, the sapphire substrate is used as the growth substrate for the nitride-based semiconductor element layer, but the present invention is not limited to this, and a substrate capable of growing a nitride-based semiconductor, for example, Si, SiC, GaAs, MgO, ZnO, spinel, GaN, etc. can be used.

In the embodiment of the present invention, TMG is used as the Ga source of the source gas and TMA is used as the Al source. However, the present invention is not limited to this. Similarly, although CP ₂ Mg is used as the Mg source of the dopant gas, it is not limited to this.

  As described above, the present invention naturally includes various embodiments not described herein. Therefore, the technical scope of the present invention is defined only by the invention specifying matters according to the scope of claims reasonable from the above description.

It is sectional drawing for demonstrating the manufacturing method of the nitride type semiconductor element which concerns on embodiment of this invention. It is a graph which shows transition of the growth temperature in the manufacturing method of the nitride type semiconductor device concerning an embodiment of the invention. It is a time chart which shows the change of the growth temperature and the supply amount of each raw material in the A stage of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 ... Substrate 102 ... N-type semiconductor layer 103 ... Active layer 104 ... AlGaN layer 105 ... First GaN layer 106 ... Second GaN layer

Claims (2)

Forming at least one nitride-based semiconductor layer on a substrate;
Forming an active layer on the nitride-based semiconductor layer;
Forming AlGaN layer on the active layer by supplying Al using a carrier gas composed of H ₂ and N _{2 at} a flow rate of N ₂ larger than H ₂ in the carrier gas ;
On the AlGaN layer, under the same conditions as the conditions for forming the AlGaN layer, stopping only the supply of Al and forming the first GaN layer;
Forming a second GaN layer on the first GaN layer using a carrier gas composed of H ₂ and N _{2 under a} condition that the flow rate of N ₂ is smaller than H ₂ in the carrier gas. A method for producing a nitride-based semiconductor device characterized by the above. The conditions similar to the conditions for forming the AlGaN layer in the step of forming the first GaN layer include the flow rate ratio between the source gas containing the nitrogen component of the nitride semiconductor and the H ₂ and the N _2. The method for producing a nitride semiconductor device according to claim 1, wherein:

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