JP2007201141A - Nitride semiconductor element and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nitride semiconductor element capable of inhibiting deterioration of InGaN layer, while improving hole concentration of a p-type semiconductor layer to improve light emission in the InGaN layer. <P>SOLUTION: The nitride semiconductor element 1 consists of an n-type semiconductor layer 3, an active layer 4, and a p-type semiconductor layer 5 and these layers are laminated on a substrate 2. The active layer 4 consists of n-type InGaN layers 13, serving as a well layer and n-type GaN layers 14 serving as a barrier layer. These two are laminated periodically. The p-type semiconductor layer 5 is formed only of a p-type InGaN layer 15 with high hole concentration, even if grown under a low growth temperature. The manufacturing method of the nitride semiconductor element 1 includes the steps of forming the active layer 4, and growing the p-type InGaN layer 15, constituting the p-type semiconductor layer 5 under a low growth temperature (approx. 850°C, for example). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a nitride semiconductor device including an active layer having an InGaN layer and a method for manufacturing the nitride semiconductor device.

  Conventionally, a nitride semiconductor device such as a light emitting diode including an active layer having an InGaN layer and a method for manufacturing the nitride semiconductor device are known.

  For example, Patent Document 1 discloses a nitride semiconductor device in which a buffer layer, an n-type GaN layer, an active layer, a p-type cladding layer, and a p-type InGaN layer are sequentially stacked on a substrate. The active layer has a multiple quantum well structure in which a well layer made of an InGaN layer and a barrier layer made of a GaN layer are periodically stacked. The p-type cladding layer is composed of a p-type GaN layer and a p-type AlGaN layer.

In the nitride semiconductor device manufacturing method, after growing a buffer layer and an n-type GaN layer on a substrate, an active layer including a well layer and a barrier layer is grown at a growth temperature of 700 ° C. Next, the growth temperature is raised to 1025 ° C. to grow a p-type GaN layer, and then the growth temperature is further raised to 1050 ° C. to grow a p-type AlGaN layer. Next, the growth temperature is lowered to 700 ° C., and a p-type InGaN layer is grown to manufacture a nitride semiconductor device.
JP 2004-14587 A

However, in the nitride semiconductor device of Patent Document 1, after growing an active layer including an InGaN layer, a p-type cladding layer is grown in a state where the growth temperature is 1000 ° C. or higher. For this reason, in the InGaN layer of the active layer having a low In solubility, In is phase-separated and deteriorates due to heat at a high growth temperature. In particular, when the InGaN layer of the active layer is an In _x Ga _1-x N layer, the composition ratio of In is such as a nitride semiconductor element for emitting blue or green light where x ≧ 0.15. In a high nitride semiconductor device, In phase separation appears remarkably. As a result, there is a problem in that light cannot be emitted in many regions in the InGaN layer of the active layer, resulting in a decrease in luminance.

  In addition, when the growth temperature of the p-type cladding layer is lowered to, for example, 1000 ° C. or lower in order to prevent the deterioration of the InGaN layer of the active layer, the residual electron concentration of the p-type GaN layer is increased, and the holes of the p-type GaN layer are increased. There was a problem that the concentration was lowered.

  The present invention has been devised to solve the above-described problems, and can improve the light emission in the InGaN layer by suppressing the deterioration of the InGaN layer while increasing the hole concentration of the p-type semiconductor layer. An object of the present invention is to provide a semiconductor device.

  In order to achieve the above object, according to the first aspect of the present invention, in the nitride semiconductor device having an active layer having an InGaN layer, the active layer is formed only of a p-type InGaN layer on the surface in the growth direction side. The nitride semiconductor device is characterized in that a p-type semiconductor layer is formed.

The invention according to claim 2 is the nitride semiconductor device according to claim 1, wherein the InGaN layer of the active layer is In _x Ga _1-x N (x ≧ 0.15). is there.

  According to a third aspect of the present invention, there is provided a first step of growing an n-type semiconductor layer on a substrate, a second step of growing an active layer including an InGaN layer on the n-type semiconductor layer, and the active layer. And a third step of growing a p-type semiconductor layer comprising only a p-type InGaN layer, and the growth temperature in the third step is 900 ° C. or lower. .

  According to a fourth aspect of the present invention, a first step of growing an n-type semiconductor layer on a substrate, a second step of growing an active layer including an InGaN layer on the n-type semiconductor layer, and the active layer And a third step of growing a p-type semiconductor layer made of only a p-type InGaN layer, and the growth temperature in the third step is 150 ° C. or lower than the growth temperature of growing the active layer in the second step. This is a method for manufacturing a nitride semiconductor device.

  According to the present invention, the surface of the active layer including the InGaN layer on the growth direction side, that is, the surface on which growth is performed after the active layer, can achieve a high hole concentration even when grown at a low growth temperature. Since the p-type semiconductor layer composed only of the p-type InGaN layer is formed, the hole concentration of the p-type semiconductor layer is increased and the InGaN layer in the active layer is caused by the high growth temperature when growing the p-type semiconductor layer. Phase separation can be suppressed. As a result, deterioration of the InGaN layer in the active layer can be prevented and light can be emitted from many regions of the InGaN layer, so that the luminance can be improved.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a cross-sectional structure of a nitride semiconductor device according to the present invention.

  In the nitride semiconductor device 1, an n-type semiconductor layer 3, an active layer 4, and a p-type semiconductor layer 5 are stacked on a substrate 2. As will be described in detail later, it is assumed that an n-type semiconductor layer 3, an active layer 4, and a p-type semiconductor layer 5 are grown on the substrate 2 in this order. In addition, an n-side electrode and a p-side electrode connected to the outside are formed on the n-type semiconductor layer 3 and the p-type semiconductor layer 5, respectively, but illustration thereof is omitted.

  The substrate 2 is made of a sapphire substrate, a GaN substrate, a SiC substrate, or the like.

  In the n-type semiconductor layer 3, an n-type AlGaN layer 11 and an n-type GaN layer 12 are stacked. The n-type AlGaN layer 11 is doped with Si, which is an n-type impurity, and has an Al composition ratio of about 10% or less. The n-type AlGaN layer 11 preferably has a thickness of about 1.2 μm or less in order to prevent cracks. The n-type GaN layer 12 is doped with Si, which is an n-type impurity. Instead of the n-type GaN layer 12, an n-type InGaN layer having an In composition ratio of about 3% or less may be applied.

  The active layer 4 has a multi-well structure in which an n-type InGaN layer 13 that is a well layer and an n-type GaN layer 14 that is a barrier layer are periodically stacked in a plurality of layers (for example, three layers).

  The n-type InGaN layer 13, which is a well layer, has a smaller band gap than the n-type semiconductor layer 3. The n-type InGaN layer 13 has a thickness of about 30 mm and is doped with Si, which is an n-type impurity.

Here, the composition ratio of In in the n-type InGaN layer 13 of the active layer 4 is not particularly limited, but when the n-type InGaN layer 13 of the active layer 4 is In _x Ga _1-x N, blue X is preferably about 0.15, and when green is emitted, x is preferably about 0.20.

  The n-type GaN layer 14 has a larger band gap than the n-type InGaN layer 13 constituting the well layer, and is for confining carriers in the well layer. The n-type GaN layer 14 is doped with Si, which is an n-type impurity.

  The p-type semiconductor layer 5 is formed on the surface of the active layer 4 on the growth direction side. The p-type semiconductor layer 5 is composed only of the p-type InGaN layer 15 doped with Mg, which is a p-type impurity. The p-type InGaN layer 15 is configured so that the In composition ratio is about 3% or less. The p-type InGaN layer 15 preferably has a thickness of about 0.5 μm or less in order to prevent the formation of holes (pits).

  In the nitride semiconductor device 1, when a voltage is applied between the n-type semiconductor layer 3 and the p-type semiconductor layer 5 via the n-side electrode and the p-side electrode, the n-type semiconductor layer 3 to the active layer 4 While electrons are injected, holes are injected from the p-type semiconductor layer 5 into the active layer 4. The electrons and holes injected into the active layer 4 are combined in the n-type InGaN layer 13 that is a well layer to emit light.

  Next, with reference to FIG. 2, a method for manufacturing the nitride semiconductor device by MOCVD will be described. FIG. 2 is a graph showing the relationship between the growth temperature and time when growing each layer of the nitride semiconductor device according to the present invention.

First, after introducing the substrate 2 into the growth chamber, the temperature of the growth chamber is set to about 1050 ° C., and the substrate 2 is cleaned in an H ₂ atmosphere containing a small amount of N ₂ .

Next, the n-type semiconductor layer 3 is grown on the substrate 2 (first step). Specifically, first, NH ₃ , H ₂ , N ₂ , TMG, TMAl, and SiH ₄ were supplied to the growth chamber while maintaining the growth temperature (the temperature of the substrate 2, the same applies hereinafter) at about 1050 ° C. The n-type AlGaN layer 11 is grown. Next, after the growth temperature is lowered to about 1000 ° C., NH ₃ , H ₂ , N ₂ , TMG, and SiH ₄ are supplied to grow the n-type GaN layer 12.

Next, the active layer 4 is grown on the n-type semiconductor layer 3 (second step). Specifically, after the growth temperature is lowered to about 750 ° C., NH ₃ , H ₂ , N ₂ , TEG, TMIn, and SiH ₄ are supplied to grow the n-type InGaN layer 13 that is a well layer. Next, with the growth temperature maintained at about 750 ° C., NH ₃ , H ₂ , N ₂ , TMG, and SiH ₄ are supplied to grow the n-type GaN layer 14 that is a barrier layer. Thereafter, while maintaining the growth temperature at about 750 ° C., the n-type InGaN layer 13 and the n-type GaN layer 14 are alternately and periodically grown by a desired number of times.

Next, the p-type semiconductor layer 5 is grown on the active layer 4 (third step). Specifically, after raising the growth temperature to about 850 ° C., NH ₃ , H ₂ , N ₂ , TMG, TMIn, and Cp ₂ Mg are supplied to grow the p-type InGaN layer 15.

  Finally, after the p-type InGaN layer 15 is grown, the growth temperature is gradually lowered to complete the nitride semiconductor device 1.

  As described above, the p-type semiconductor layer 5 including only the p-type InGaN layer 15 that can be grown at a low growth temperature on the upper surface (surface on the growth direction side) of the active layer 4 including the n-type InGaN layer 13. Is forming. For this reason, when the p-type semiconductor layer is composed of a p-type GaN layer or the like, the n-type InGaN layer 13 in the active layer 4 caused by a high growth temperature (about 950 ° C. or higher) when the p-type GaN layer is grown. Phase separation can be suppressed. Thereby, degradation of the n-type InGaN layer 13 in the active layer 4 can be prevented. Therefore, since light can be emitted from many regions of the n-type InGaN layer 13 of the active layer 4, the brightness of the nitride semiconductor device 1 can be improved.

  Further, by forming the p-type semiconductor layer 5 with the p-type InGaN layer 15 that can increase the hole concentration even when grown at a low temperature, the p-type InGaN is formed at a low growth temperature (about 850 ° C.) as described above. Even when the layer 15 is grown, the p-type semiconductor layer 5 can maintain a high hole concentration.

  Next, an experiment conducted to prove the above effect will be described.

  First, a comparative nitride semiconductor element 51 manufactured for comparison with the nitride semiconductor element 1 according to the present invention will be described with reference to FIGS. 3 and 4.

  FIG. 3 is a diagram showing a cross-sectional structure of a comparative nitride semiconductor device. FIG. 4 is a diagram showing the relationship between the growth temperature and time when growing each layer of the comparative nitride semiconductor device.

  As shown in FIG. 3, a comparative nitride semiconductor device 51 includes a substrate 52, an n-type semiconductor layer 53 including an n-type AlGaN layer 61 and an n-type GaN layer 62, and an n-type InGaN layer that is a well layer. 63, an active layer 54 including an n-type GaN layer 64 serving as a barrier layer, and a p-type semiconductor layer 55 are stacked. The p-type semiconductor layer 55 is constituted by a p-type GaN layer 65 doped with Mg, which is a p-type impurity. The substrate 52, the n-type semiconductor layer 53, and the active layer 54 have the same configuration as the substrate 2, the n-type semiconductor layer 3, and the active layer 4 of the nitride semiconductor device 1 according to the present invention.

As shown in FIG. 4, in the manufacturing method of the comparative nitride semiconductor device 51, the layers up to the active layer 54 were manufactured in the same manner as the nitride semiconductor device 1 according to the present invention described above. Then, after forming the active layer 54, NH ₃ , H ₂ , N ₂ , TEG, and Cp ₂ Mg are supplied in a state where the growth temperature is raised to about 950 ° C. to grow the p-type GaN layer 65. A comparative nitride semiconductor device 51 was produced.

  Next, referring to FIG. 5, the hole concentration of the p-type InGaN layer 15 of the p-type semiconductor layer 5 of the nitride semiconductor device 1 according to the present invention described above and the p-type semiconductor layer of the comparative nitride semiconductor device 51 are described. The result of comparing the hole concentrations of 55 p-type GaN layers 65 will be described.

  FIG. 5 is a graph showing the hole concentration of the p-type InGaN layer of the nitride semiconductor device of the present invention and the hole concentration of the p-type GaN layer of the comparative nitride semiconductor device. In FIG. 5, what is plotted with squares indicates the hole concentration of the p-type InGaN layer 15 of the nitride semiconductor element 1 of the present invention, and what is plotted with rhombuses is the p-type GaN of the comparative nitride semiconductor element 51. The hole concentration of the layer 65 is shown. The p-type InGaN layer 15 of the nitride semiconductor device 1 of the present invention has an In composition ratio of 3.5% and a thickness of about 0.17 μm. The p-type InGaN layer 65 of the comparative nitride semiconductor element 51 has a thickness of about 0.39 μm.

As shown in FIG. 5, the hole concentration in the p-type GaN layer 65 of the comparative nitride semiconductor element 51 was about 7.05 × 10 ¹⁷ / cm ³ or less, whereas the nitride semiconductor according to the present invention was used. The hole concentration in the p-type InGaN layer 15 of the element 1 showed a high value of about 11.1 × 10 ¹⁷ / cm ³ or more. As described above, the p-type InGaN layer 15 of the nitride semiconductor device 1 according to the present invention has a high growth temperature (about 950 ° C.) although the p-type InGaN layer 15 is grown at a low growth temperature (about 850 ° C.). The hole concentration can be made higher than that of the p-type InGaN layer 65 of the comparative nitride semiconductor element 51 grown in step 1).

  Next, a description will be given of the results of an experiment comparing the state of light emission when a voltage is applied to the above-described nitride semiconductor device 1 according to the present invention and the comparative nitride semiconductor device 51.

  FIG. 6 is an image obtained by observing the nitride semiconductor device according to the present invention, to which a voltage has been applied, with a fluorescence microscope. FIG. 7 is an image obtained by observing a comparative nitride semiconductor element to which a voltage is applied, with a fluorescence microscope.

  As shown in FIG. 6, it can be seen that an image obtained by observing the nitride semiconductor device 1 according to the present invention emits light in all regions. In the actually observed color image, yellow or green light emission was observed.

  On the other hand, as shown in FIG. 7, in the image obtained by observing the comparative nitride semiconductor element 51, light emission is not observed in most regions, and only weak light is observed in regions where light emission is observed. In the actually observed color image, only dark yellow or dark green light emission was observed even in the light emitting region.

  From these results, in the nitride semiconductor device 1 according to the present invention, after the active layer 4 is formed, the p-type InGaN layer 15 constituting the p-type semiconductor layer 5 is grown at a low growth temperature (about 850 ° C.). Since the phase separation of the n-type InGaN layer 13 of the active layer 4 could be suppressed, it is considered that light could be emitted in many regions of the active layer 4.

  On the other hand, in the comparative nitride semiconductor device 51, after forming the active layer 54, the p-type GaN layer 65 constituting the p-type semiconductor layer 55 is grown at a high growth temperature (about 950 ° C.). The phase separation of the 54 n-type InGaN layers 65 occurred in many regions. For this reason, it is considered that light could not be emitted in most regions of the active layer 54.

  Although the present invention has been described in detail using the above-described embodiments, it will be apparent to those skilled in the art that the present invention is not limited to the embodiments described in this specification. The present invention can be implemented as modifications and changes without departing from the spirit and scope of the present invention defined by the description of the scope of claims. Therefore, the description of the present specification is for illustrative purposes and does not have any limiting meaning to the present invention. Hereinafter, modified embodiments in which the above-described embodiment is partially modified will be described.

  For example, in the embodiment described above, the p-type InGaN layer 15 of the p-type semiconductor layer 5 is grown at a growth temperature of about 850 ° C., but the growth temperature of the p-type InGaN layer 15 is limited to about 850 ° C. If it is about 900 degrees C or less, the effect mentioned above can be show | played.

  In the above-described embodiment, the difference between the growth temperature of the active layer 4 (about 750 ° C.) and the growth temperature of the p-type semiconductor layer 5 (about 850 ° C.) was about 100 ° C. The difference in temperature is not limited to about 100 ° C., and if the difference between the two growth temperatures is about 150 ° C. or less, the above-described effects can be obtained.

  Moreover, the configuration of each layer of the nitride semiconductor device 1 described above can be changed as appropriate.

  Moreover, the manufacturing process of the nitride semiconductor device 1 described above can be changed as appropriate.

1 shows a cross-sectional structure of a nitride semiconductor device according to the present invention. It is the figure which showed the relationship between the growth temperature at the time of growing each layer of the nitride semiconductor element by this invention, and time. 2 shows a cross-sectional structure of a comparative nitride semiconductor device. It is the figure which showed the relationship between the growth temperature at the time of growing each layer of the nitride semiconductor element for a comparison, and time. It is a graph which shows the hole concentration of the p-type InGaN layer of the nitride semiconductor element of this invention, and the hole concentration of the p-type GaN layer of the nitride semiconductor element for a comparison. It is the image which observed the nitride semiconductor element by this invention to which the voltage was applied with the fluorescence microscope. It is the image which observed the comparative nitride semiconductor element to which the voltage was applied with the fluorescence microscope.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Nitride semiconductor element 2 Substrate 3 n-type semiconductor layer 4 Active layer 5 p-type semiconductor layer 11 n-type AlGaN layer 12 n-type GaN layer 13 n-type InGaN layer 14 n-type GaN layer 15 p-type InGaN layer

Claims (4)

In a nitride semiconductor device including an active layer having an InGaN layer,
A nitride semiconductor device, wherein a p-type semiconductor layer made of only a p-type InGaN layer is formed on a surface of the active layer on the growth direction side. 2. The nitride semiconductor device according to claim 1, wherein the InGaN layer of the active layer is In _x Ga _1-x N (x ≧ 0.15). A first step of growing an n-type semiconductor layer on the substrate;
A second step of growing an active layer including an InGaN layer on the n-type semiconductor layer;
A third step of growing a p-type semiconductor layer made of only a p-type InGaN layer on the active layer,
The method for manufacturing a nitride semiconductor device, wherein a growth temperature in the third step is 900 ° C. or lower. A first step of growing an n-type semiconductor layer on the substrate;
A second step of growing an active layer including an InGaN layer on the n-type semiconductor layer;
A third step of growing a p-type semiconductor layer made of only a p-type InGaN layer on the active layer,
The growth temperature in the third step is 150 ° C. or lower than the growth temperature for growing the active layer in the second step.