JP4742791B2 - Method for p-type activation of group III nitride compound semiconductor - Google Patents

Description

The present invention relates to a method for p-type activation of a group III nitride compound semiconductor to which a p-type impurity is added.
This method is very useful for reducing the electrical resistance of the p-type semiconductor layer based on the promotion of p-type activation of the p-type semiconductor layer.

As a method for p-type activation of the p-type semiconductor layer of the semiconductor element, a method of annealing exclusively has been conventionally employed. As a conventional technique for performing such annealing, for example, one described in Patent Document 1 below is known.
Japanese Patent No. 2540791

However, it is difficult to increase the carrier concentration of the p-type semiconductor layer to 5 × 10 ¹⁸ cm ⁻³ or more only with the above-described conventional technology. This is because, with the above-described conventional technology alone, some protons (H ⁺ ) remain in p-type impurities such as magnesium ions (Mg ⁻ ) in the p-type semiconductor layer while being constrained. Conceivable.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to promote the p-type activation of the p-type semiconductor layer by increasing the carrier concentration of the p-type semiconductor layer as compared with the prior art. It is.

In order to solve the above problems, the following means are effective.
That is, the first means of the present invention provides a first method of applying a potential to the back side of a group III nitride compound semiconductor in a method of p-type activation of a group III nitride compound semiconductor to which a p-type impurity is added. The thin film metal layer is formed on the surface of the group III nitride compound semiconductor, the group III nitride compound semiconductor is placed in the electrolytic solution, and the first electrode is higher than the thin film metal layer. By applying a voltage so as to be at a potential, a voltage is applied between the front and back surfaces of the group III nitride compound semiconductor, so that protons (H ⁺ ) in the group III nitride compound semiconductor are removed. It is drawn out to the surface of the group III nitride compound semiconductor and released into the electrolytic solution.

However, in the above-mentioned “applying a voltage between the front and back surfaces of a group III nitride compound semiconductor”, an electrode or the like is directly provided on both the front and back surfaces of the group III nitride compound semiconductor and a voltage is applied. In addition, other semiconductors or solutions are interposed between the two voltage application points between which the group III nitride compound semiconductor is sandwiched, so that it is indirectly between the front and back surfaces of the group III nitride compound semiconductor. It also includes applying a voltage.
The second means of the present invention is that, in the first means, the material of the thin film metal layer is gold (Au), platinum (Pt), or rhodium (Rh) .

The third means of the present invention is a laminate in which a group III nitride compound semiconductor layer to which an n-type impurity is added and a group III nitride compound semiconductor layer to which a p-type impurity is added are stacked on a substrate. In the method of activating the group III nitride compound semiconductor layer to which the p-type impurity is added, the group III nitride compound semiconductor layer to which the p-type impurity is added is annealed to obtain p-type activity. And etching the stack from the side of the group III nitride compound semiconductor layer to which the p-type impurity has been added to expose the group III nitride compound semiconductor layer to which the n-type impurity has been added. to form a first electrode for applying a potential, through the electrolytic solution, the opposing electrodes for applying a potential to the p-type impurity is added group III nitride compound semiconductor layer surface provided, the electrolyte laminate And the first electrode has a higher potential than the counter electrode. That by applying a voltage so as, protons are in the p-type impurity is added Group III nitride compound semiconductors (H ⁺⁾ in the electrolyte is pulled out to the surface of the group III nitride compound semiconductor It is a p-type activation method for a group III nitride compound semiconductor characterized in that it is released.

Furthermore, a fourth means of the present invention is to generate hydrogen (H ₂ ) gas in the electrolytic solution based on the three-electrode method using a reference electrode in any one of the first to third means. By optimizing the potential of the surface to be produced, the reaction of detaching protons (H ⁺ ) from the group III nitride compound semiconductor is promoted.
By the above means of the present invention, the above-mentioned problem can be effectively or rationally solved.

The effects obtained by the above-described means of the present invention are as follows.
That is, according to the first means of the present invention, at least a part of the protons (H ⁺ ) remaining in the group III nitride compound semiconductor restrained by the p-type impurity or the like are group III nitride. Since it can be forcibly taken out from an organic compound semiconductor into an electrolytic solution by using electric force, this effectively promotes the p-type activation of this group III nitride compound semiconductor as compared with the prior art. Can do. At this time, since the potential difference between the thin film metal layer and the first electrode can be set directly without using the electrolytic solution, the electric field in the group III nitride compound semiconductor is more effectively formed. be able to. For this reason, said electric force can be generated more effectively.
Further, according to the second means of the present invention, the above-mentioned thin film metal layer is effective in a non-equilibrium state between protons (ie, 2H ⁺ and 2e ⁻ ) and hydrogen gas (: H ₂ ). Since it exhibits a catalytic action, the generation efficiency of hydrogen gas can be more effectively increased.

  According to the third means of the present invention, the group III nitride compound semiconductor layer to which the n-type impurity is added and the group III nitride compound semiconductor layer to which the p-type impurity is added are stacked on the substrate. In the method of p-type activation of the group III nitride compound semiconductor layer to which the p-type impurity is added, the p-type impurity is added by using the first electrode and the counter electrode. Since a group III nitride compound semiconductor to which a p-type impurity is added can be effectively p-type activated without forming a thin film metal layer on the surface of the group III nitride compound semiconductor, the group III As compared with other methods of forming a thin film metal layer on the surface of a nitride-based compound semiconductor, it is possible to ensure a higher degree of arbitrary structure of the desired group III nitride-based compound semiconductor finally obtained.

According to the fourth means of the present invention, the potential difference with respect to the electrolyte solution on the surface where hydrogen gas is generated or the absolute potential on the surface where hydrogen gas is generated can be easily adjusted to a desired value. Therefore, by the optimization, the generation efficiency of hydrogen gas can be more effectively increased in a non-equilibrium state between protons (ie, 2H ⁺ and 2e ⁻ ) and hydrogen gas (: H ₂ ).

Hereinafter, the present invention will be described based on specific examples.
However, the embodiments of the present invention are not limited to the following examples.

FIG. 1 is a schematic circuit diagram of electrolysis showing the p-type activation processing method of the first embodiment. A light-emitting diode 100 comprising a crystal growth substrate 101, a semiconductor layer 102, a p-type semiconductor layer 103, etc. An LED having a known structure such as a heterojunction is schematically shown. On the crystal growth surface (right side of the drawing) of the crystal growth substrate 101 of the light emitting diode 100, a semiconductor layer 102 composed of an n-type semiconductor layer, a light emitting layer, and the like is laminated, and further on that (right side of the drawing). The p-type semiconductor layer 103 made of a group III nitride compound semiconductor to which a p-type impurity is added is laminated. The p-type semiconductor layer 103 may have a single-layer structure or a multi-layer structure. By adding magnesium (Mg) and performing an annealing process similar to the conventional one, the p-type semiconductor layer 103 is previously converted to a p-type structure as in the prior art. It has been activated.
However, this annealing process is not necessarily performed.

  A negative electrode 104 of the LED is formed on the etched exposed surface of the n-type semiconductor layer of the semiconductor layer 102, and this negative electrode 104 corresponds to the first electrode of the present invention. The negative electrode 104 is locally sealed with a sealing material 105. In the light emitting diode 100, at least the upper surface of the p-type semiconductor layer 103 is immersed in the electrolytic solution 2. Hereinafter, the upper surface of the p-type semiconductor layer 103 is referred to as a contact surface 103a for the reason that an electrode is formed later. The contact surface 103a corresponds to the surface of the group III nitride compound semiconductor of the present invention.

The electrolytic solution 2 is made of an aqueous hydrochloric acid solution and is diluted to about pH2. However, the electrolytic solution 2 may be composed of other aqueous solutions such as sulfuric acid.
The counter electrode 3 is made of carbon or platinum, and is connected to the negative electrode 104 via the constant voltage power source E by wires 4 and 5. That is, the negative electrode 104 is at a positive potential relative to the counter electrode 3 based on the voltage applied by the constant voltage power source E.
In view of production efficiency, these circuits are preferably configured not in units of semiconductor elements but in units of semiconductor wafers before separation.

With the above configuration, the following chemical reactions are promoted near the contact surface 103a and near the counter electrode 3, respectively.
(Chemical reaction in the vicinity of the contact surface 103a)
2H ⁺ + 2OH ⁻ → 2H ₂ O (1)
(Chemical reaction in the vicinity of the counter electrode 3)
2H ₂ O + 2e ⁻ → 2OH ⁻ + H ₂ ↑ (2)

A large number of protons (H ⁺ ) can be released from the p-type semiconductor layer 103 by these chemical reactions. Therefore, according to the above configuration, the p-type activation of the p-type semiconductor layer 103 can be greatly promoted compared to the conventional case.
After this p-type activation process, the semiconductor wafer is washed and dried, and thereafter, the positive electrode is formed or divided into element units in the same manner as in the prior art. A light-emitting diode with low resistance can be obtained.

FIG. 2 is a schematic circuit diagram of electrolysis showing the p-type activation processing method of the second embodiment. On the crystal growth surface (right side of the drawing) of the crystal growth substrate 201 of the light emitting diode 200, a semiconductor layer 202 composed of an n-type semiconductor layer, a light emitting layer, and the like is laminated, and further (on the right side of the drawing). The p-type semiconductor layer 203 is stacked. This p-type semiconductor layer 203 is activated to a p-type in advance to the conventional level by adding magnesium (Mg) and performing the same annealing treatment as in the past.
However, this annealing process is not necessarily performed.

  A negative electrode 204 is formed on the etched exposed surface of the n-type semiconductor layer included in the semiconductor layer 202, and the negative electrode 204 corresponds to the first electrode of the present invention. The negative electrode 204 is locally sealed with a sealing material 205. A thin-film metal layer 206 made of several layers of gold (Au) is formed on the upper surface (contact surface 203a) of the p-type semiconductor layer 203, and a positive electrode 207 is formed thereon. ing. The positive electrode 207 is also locally sealed by the sealing material 208.

In the light emitting diode 200, at least the exposed surface of the thin film metal layer 206 is immersed in the electrolytic solution 2. The electrolytic solution 2 is made of an aqueous hydrochloric acid solution and is diluted to about pH2. However, the electrolytic solution 2 may be composed of other aqueous solutions such as sulfuric acid.
The positive electrode 207 is connected to the negative electrode 104 via the constant voltage power source E by the wirings 4 and 5. That is, the negative electrode 204 is at a positive potential relative to the positive electrode 207 based on the voltage applied by the constant voltage power source E.
In view of production efficiency, these circuits are preferably configured not in units of semiconductor elements but in units of semiconductor wafers before separation.

With the above configuration, the following chemical reaction is promoted near the interface between the thin-film metal layer 206 and the electrolytic solution 2.
(Chemical reaction in the vicinity of the thin metal layer 206)
2H ⁺ + 2e ⁻ → H ₂ ↑ (3)

A large number of protons (H ⁺ ) can be released from the p-type semiconductor layer 203 by these chemical reactions. Therefore, according to the above configuration, the p-type activation of the p-type semiconductor layer 203 can be greatly promoted as compared with the conventional case.
After this p-type activation treatment, the semiconductor wafer is washed and dried, and thereafter, through a process of dividing into element units as in the past, it is possible to obtain a light emitting diode having a smaller electrical resistance than in the past. it can.

[Other variations]
The embodiment of the present invention is not limited to the above-described embodiment, and other modifications as exemplified below may be made. Even with such modifications and applications, the effects of the present invention can be obtained based on the functions of the present invention.
(Modification 1)
For example, although the reference electrode was not used in Example 2 described above, a reference electrode may be further introduced according to the three-electrode method (fourth means of the present invention). As a result, the absolute potential of the surface where the hydrogen gas is generated can be easily adjusted to a desired value. Therefore, by optimizing the proton or the like in the vicinity of the surface where the hydrogen gas is generated (ie, 2H ⁺ and 2e ⁻ ) and hydrogen gas (H ₂ ), the generation efficiency of hydrogen gas can be more effectively increased in a non-equilibrium state (eg, formula (3)). Therefore, in this case, the desired group III nitride compound semiconductor can be activated p-type more efficiently and effectively.

In this case, the potential of the surface where the hydrogen gas is generated (for example, the potential of the thin film metal layer 206) is the thermodynamic equilibrium potential of the electrochemical reaction of the following formula (3) ′ (: the potential V0 of the standard hydrogen electrode). It is desirable to set the potential to be lower than that of the thermodynamic equilibrium potential (V0 + 1.23 V) of the electrochemical reaction (: electrolysis of water) of the following formula (4). . Further, if the dissolved oxygen in the solution is removed by dry nitrogen bubbling or the like, the above-mentioned potential can be made lower, so that the desired p-type activation treatment can be performed more efficiently and effectively.
(Expression of equilibrium state of electrochemical reaction)
2H ⁺ + 2e ⁻ ⇔ H ₂ (3) ′
_{O 2 + H 2 O + 2e} - ⇔ HO 2 - + OH - ... (4)

  In each of the above embodiments, the p-type activation method of each p-type semiconductor layer (103, 203) in the light-emitting diodes 100, 200 has been illustrated. Of course, the present invention can be applied to a single group III nitride compound semiconductor having a multilayer structure in substantially the same manner.

At this time, for example, when the counter electrode is used in substantially the same manner as in FIG. 1, the surface of the p-type group III nitride compound semiconductor facing the counter electrode is the front surface, and the opposite surface (back surface) is the back surface. The first electrode of the present invention corresponding to the negative electrode 104 may be formed on the back surface of the p-type group III nitride compound semiconductor.
Further, when the thin film metal layer (206) is used in substantially the same manner as in FIG. 2, the opposite side (back side) of the thin film metal layer (206) is used as the back side, and the negative electrode described above is formed on the back side of the p-type group III nitride compound semiconductor. The first electrode of the present invention corresponding to the electrode 204 may be formed.

  The present invention relates to a method for p-type activation of a group III nitride compound semiconductor to which a p-type impurity is added. Therefore, the application field is not limited to the light emitting element and the light receiving element, and the present invention can be used for any semiconductor element having a group III nitride compound semiconductor.

Electrolytic circuit diagram showing the p-type activation processing method of Example 1 Electrolytic circuit diagram showing the p-type activation processing method of Example 2

100, 200: Light emitting diode 101, 201: Crystal growth substrate 102, 202: Semiconductor layer (n-type semiconductor layer and light emitting layer)
103, 203: p-type semiconductor layer 104, 204: negative electrode 105, 205: sealing material
206: Thin metal layer
207: Positive electrode
2: Electrolytic solution

Claims (4)

In a method for p-type activation of a group III nitride compound semiconductor to which a p-type impurity is added,
Providing a first electrode for applying a potential to the back side of the group III nitride compound semiconductor;
Forming a thin metal layer on the surface of the group III nitride compound semiconductor;
Put the group III nitride compound semiconductor in the electrolyte,
By applying a voltage between the front and back surfaces of the group III nitride compound semiconductor by applying a voltage so that the first electrode has a higher potential than the thin film metal layer, the group III nitride P-type activation of a group III nitride compound semiconductor, characterized in that protons (H ⁺ ) in a group III compound semiconductor are drawn out to the surface of the group III nitride compound semiconductor and released into the electrolytic solution Method. 2. The method of activating a group III nitride compound semiconductor according to claim 1, wherein the material of the thin film metal layer is gold (Au), platinum (Pt), or rhodium (Rh). . A layered product in which a group III nitride compound semiconductor layer to which an n-type impurity is added and a group III nitride compound semiconductor layer to which a p-type impurity is added is laminated on a substrate is added with the p-type impurity III In the method of activating the group nitride compound semiconductor layer by p-type activation,
Annealing the III-nitride compound semiconductor layer to which the p-type impurity is added to perform p-type activation;
Wherein from the side of the p-type impurity is added Group III nitride compound semiconductor layer by etching the laminate, exposing the group III nitride compound semiconductor layer in which the n-type impurity is added, the exposed surface a first electrode for applying a potential is formed on,
Through the electrolytic solution, it provided the opposing electrodes for applying a potential to the p-type impurity is added Group III nitride compound semiconductor layer surface,
Put the laminate into the electrolyte,
By applying a voltage so that the first electrode has a higher potential than the counter electrode, protons (H ⁺ ) in the group III nitride compound semiconductor to which the p-type impurity is added are A p-type activation method for a group III nitride compound semiconductor, characterized in that the group III nitride compound semiconductor is drawn to the surface of the group III nitride compound semiconductor and released into the electrolytic solution. Based on the three-electrode method using a reference electrode,
By optimizing the potential of the surface that generates hydrogen (H ₂ ) gas in the electrolyte,
The group III nitride compound semiconductor according to any one of claims 1 to 3, which promotes a reaction in which protons (H ⁺ ) are eliminated from the group III nitride compound semiconductor. p-type activation method.

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