JP3150016B2 - Method for manufacturing semiconductor light emitting device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor light emitting device. More specifically, the present invention relates to a method for manufacturing a semiconductor light emitting device in which an n-type semiconductor layer and a p-type semiconductor layer are grown on a semiconductor substrate by a liquid phase epitaxial growth method.

[0002]

2. Description of the Related Art As a semiconductor light emitting device, as shown in FIG. 4, an n-type GaAs substrate 101 is formed by a liquid-phase epitaxial growth method in which an n-type epitaxial layer 102 and a p-type epitaxial layer 103 are sequentially stacked. Light emitting diodes are known.

The n-type epitaxial layer 102 and the p-type epitaxial layer 103 are formed as follows. That is, while the substrate 101 is in contact with the GaAs melt doped with a predetermined amount of Si, the substrate 101 is gradually cooled to grow the n-type epitaxial layer 102 first, and then grow the p-type epitaxial layer 103 by natural inversion. ing.

[0004] Si (IV) is formed by a liquid phase epitaxial growth method.
When growing GaAs (III-V compound semiconductor) using a group III element as a dopant, the conductivity type of the grown layer is n-type because Si enters the Ga site at high temperatures, and p-type because Si enters the As site at low temperatures. Type. By utilizing this phenomenon, as described above, an infrared light emitting diode is manufactured at low cost by using one kind of melt.

[0005]

According to the liquid phase epitaxial growth method, the p-type epitaxial layer 1
When growing 03, the Si concentration sharply increases as the growth proceeds. Therefore, the p-type epitaxial layer 1
03 near the surface, the impurity concentration (Si concentration) is 10 ¹⁹ c
m ^−3, and as a result, the energy level is degenerated and the band gap is narrowed. When the band gap is narrowed in this manner, light emitted at the junction between the n-type epitaxial layer 102 and the p-type epitaxial layer 103 during operation is
Absorption near the surface of the p-type epitaxial layer 103 causes a problem that the emission intensity of the device is reduced.

Accordingly, an object of the present invention is to provide a method of manufacturing a semiconductor light emitting device capable of suppressing an increase in impurity concentration in a growth layer when an n-type semiconductor layer and a p-type semiconductor layer are grown by a liquid phase epitaxial growth method. It is in.

[0007]

In order to achieve the above object, a method for manufacturing a semiconductor light emitting device according to the present invention comprises contacting a substrate with a gallium arsenide melt doped with a predetermined amount of silicon by a liquid phase epitaxial growth method. In the method for manufacturing a semiconductor light-emitting device, in which the n-type semiconductor layer is grown on the substrate by slow cooling while the p-type semiconductor layer is grown by natural inversion,
At the point of time when the layer is grown to a thickness of 0 μm, while cooling slowly, the atmosphere surrounding the substrate and the melt is placed so that the increase in the concentration of silicon taken in the p-type semiconductor layer is slowed down. It is characterized by introducing ammonia gas.

In one embodiment of the present invention, the method of manufacturing a semiconductor light-emitting device is characterized in that the concentration of silicon introduced into the p-type semiconductor layer during growth reaches 10 ¹⁹ cm ^-3 before reaching the concentration of 10 ¹⁹ cm ^-3.
The method is characterized in that the growth is stopped when the mold semiconductor layer reaches a predetermined thickness.

[0009]

According to the method for manufacturing a semiconductor light emitting device of the present invention, p
When the mold semiconductor layer is grown to a thickness of 10 to 20 μm, ammonia gas is introduced into the atmosphere surrounding the substrate and the melt while gradually cooling to convert the silicon in the melt into nitride. Thereby, the concentration of silicon in the melt is reduced as compared with the prior art, so that the increase in the concentration of silicon taken into the p-type semiconductor layer during growth is reduced. Thereby, the thickness of the p-type semiconductor layer is set to several tens μm.
In the case where the silicon concentration is within the range of about 100 μm (level set in a general semiconductor light emitting device), the silicon concentration does not exceed 10 ¹⁹ cm ⁻³ near the surface of the p-type semiconductor layer, and the high impurity The generation of a degenerate layer due to the concentration does not occur, and the energy band gap is prevented from being narrowed. Therefore, during operation, light emitted at the junction surface between the n-type semiconductor layer and the p-type semiconductor layer (hereinafter, referred to as “pn junction”) is not absorbed near the surface of the p-type semiconductor layer and is directly outside the chip. Outgoing to Therefore, the light emission intensity of the element is higher than in the related art.

In operation, the distance (diffusion distance) at which minority carriers (electrons) diffuse from the pn junction into the p-type semiconductor layer is estimated to be about 10 μm. If ammonia gas is introduced before the p-type semiconductor layer grows by the diffusion distance, nitrogen atoms may be doped within the diffusion distance, and the light emitting characteristics of the device may be impaired.
On the other hand, it is meaningless to introduce ammonia gas after the impurity concentration of the p-type semiconductor layer exceeds 10 ¹⁹ cm ^-3 .
Therefore, the ammonia gas is introduced at the time when the p-type semiconductor layer grows about 10 to 20 μm.

In one embodiment of the present invention, in the method of manufacturing a semiconductor light emitting device, the p-type semiconductor layer before the concentration of silicon taken into the p-type semiconductor layer as it grows reaches 10 ¹⁹ cm ^-3. Since the growth is stopped when the thickness reaches a predetermined thickness, in the manufactured semiconductor light emitting device, the energy band gap is reliably prevented from being reduced near the surface of the p-type semiconductor layer. Is reliably prevented from being absorbed near the surface of the p-type semiconductor layer.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a method for manufacturing a semiconductor light emitting device according to the present invention will be described in detail with reference to embodiments.

FIG. 2 shows a carbon boat for performing liquid phase epitaxial growth. This boat comprises a boat body 32 having a substrate receiving portion 32a and a melt reservoir 3.
It has a boat slider 33 having 3a. The boat slider 33 can be slid with respect to the boat body 32 by a slide bar 35.

It is assumed that a GaAs infrared light emitting diode is manufactured using this boat.

First, an n-type GaAs substrate 1 is set in a substrate receiving portion 32a, and a GaAs melt 31 doped with Si element and GaAs polycrystal is set in a melt reservoir 33a, respectively. (Not shown). By elevating the temperature of the electric furnace, as shown in FIG. 3, the predetermined time (time t ₀ ~
The temperature is kept at 920 ° C. for t ₁ ).

Next, at 2.0 ° C./min. Immediately (time t ₁ ), and immediately or after several minutes, the boat slider 33 shown in FIG. 2 is slid with respect to the boat body 32 to bring the melt 31 into contact with the surface of the GaAs substrate 1. Let it. Thus, an n-type epitaxial layer 2 is grown on the surface of the GaAs substrate 1 as shown in FIG.

[0017] n-type after the growth of the epitaxial layer 2, by natural inversion in the p-type epitaxial layer 3 a of 10~20μm thickness (3a partial) growth of course grown at time t _2,
As shown in FIG. 3, ammonia gas (N
H ₃ ). Thereby, the Si element in the melt is converted into a nitride, and the Si concentration is reduced. Then, until time t ₃ , as shown in FIG. 1A, the surface-side portion 3b of the p-type epitaxial layer 3 is grown.

When a GaAs infrared light emitting diode is manufactured in this manner, an impurity profile as shown by a solid line in FIG. 1B is obtained. That is, the GaAs substrate 1
The impurity concentration N ₁ of is constant. The impurity concentration N ₂ of the n-type epitaxial layer 2 monotonously decreases toward the surface side (that is, as it grows). The degree of the decrease gradually increases toward the surface side. The impurity concentration of the p-type epitaxial layer 3 monotonously increases toward the surface side. The degree of the increase is as steep in the 3a portion (impurity concentration N _3a ) grown without flowing NH ₃ as in the conventional case, but is increased in the 3b portion (impurity concentration N _3b ) grown by flowing NH _3. Is slower than
The broken line in the figure indicates a conventional impurity profile, and DG indicates a degenerated portion. ). As a result, the Si concentration near the surface of the p-type epitaxial layer 3 was 10 ¹⁹ cm ^−3.
It becomes below. That is, a degenerate layer caused by the high impurity concentration is not generated, and the energy gap is prevented from being narrowed. Therefore, during operation, n-type epitaxial layer 2
The light emitted at the junction between the p-type epitaxial layer 3 and
The light is emitted out of the chip without being absorbed near the surface of the type epitaxial layer 3. Therefore, the emission intensity of the element can be increased as compared with the related art.

[0019]

As is clear from the above description, in the method for manufacturing a semiconductor light emitting device of the present invention, when the p-type semiconductor layer is grown to a thickness of 10 to 20 μm, the substrate and the melt are gradually cooled. Ammonia gas is introduced into the atmosphere surrounding the liquid so that the increase in the concentration of silicon taken in the p-type semiconductor layer with growth is slowed down. μm to 100μm
When the concentration is within the range (a level set in a general semiconductor light emitting device), the silicon concentration does not exceed 10 ¹⁹ cm ⁻³ near the surface of the p-type semiconductor layer, and the impurity concentration becomes high. The resulting degenerate layer is not generated, and the energy band gap is prevented from being narrowed. Therefore, during operation, light emitted from the pn junction is emitted out of the chip without being absorbed near the surface of the p-type semiconductor layer. Therefore, the emission intensity of the element can be increased as compared with the related art.

In one embodiment of the present invention, the p-type semiconductor layer before the concentration of silicon taken in the p-type semiconductor layer during growth reaches 10 ¹⁹ cm ^-3 with growth. Since the growth is stopped when the thickness reaches a predetermined thickness, in the manufactured semiconductor light emitting device, the energy band gap is reliably prevented from being reduced near the surface of the p-type semiconductor layer. Is reliably prevented from being absorbed near the surface of the p-type semiconductor layer.

[Brief description of the drawings]

FIG. 1 is a diagram showing a cross section and an impurity concentration profile of a semiconductor light emitting device manufactured by a manufacturing method according to an embodiment of the present invention.

FIG. 2 is a view showing a carbon boat used in the above manufacturing method.

FIG. 3 is a diagram showing a lapse of time of a growth temperature during liquid phase epitaxial growth.

FIG. 4 is a diagram showing a cross section of a semiconductor light emitting device manufactured by a conventional manufacturing method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 n-type GaAs substrate 2 n-type epitaxial layer 3 p-type epitaxial layer 3 a junction-side portion 3 b surface-side portion

Claims (2)

(57) [Claims] In a state where a substrate is brought into contact with a gallium arsenide melt doped with a predetermined amount of silicon by a liquid phase epitaxial growth method, the substrate is gradually cooled to grow an n-type semiconductor layer on the substrate. In a method of manufacturing a semiconductor light emitting device in which a p-type semiconductor layer is grown by natural inversion, when the p-type semiconductor layer is grown to a thickness of 10 to 20 μm, the p-type semiconductor layer is taken into the p-type semiconductor layer as the growth proceeds A method for producing a semiconductor light emitting device, characterized in that ammonia gas is introduced into an atmosphere surrounding the substrate and the melt while performing slow cooling so that an increase in the concentration of silicon is slowed down. 2. The method for manufacturing a semiconductor light emitting device according to claim 1, wherein the concentration of silicon taken into the p-type semiconductor layer during growth reaches 10 ¹⁹ cm ^−3. A method for manufacturing a semiconductor light emitting device, wherein the growth is stopped when the layer reaches a predetermined thickness.