JP3376007B2 - 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 semiconductor light emitting device having an active layer made of an InGaAlP-based material, and an object of the present invention is to provide a semiconductor light emitting device capable of stably improving luminous efficiency.

[0002]

2. Description of the Related Art A semiconductor light emitting device having an active layer made of InGaAlP material is disclosed in Japanese Patent Laid-Open No. 4-2124.
As described in No. 79, the carrier concentration and the film thickness of the active layer are specified.

[0003] For the carrier concentration in the active layer, defined as 5 × 10 ¹⁶ Quai / cm ³ at 1 × 10 ¹⁷ Quai / cm ^3, N-type in P-type, and for the film thickness is from 0.15 to 0. 75μ
It is defined as m. However, in particular, regarding the carrier concentration, both are apparent concentrations in consideration of compensation of P-type and N-type impurities or a relatively deep level.
When the carrier concentration and the quantum efficiency of the light emitting device are taken into consideration, the characteristic correlation cannot be obtained and stable light emitting characteristics cannot be obtained.

[0004]

The inventor of the present invention is InGa
A light emitting device having an active layer made of an AlP-based material has been developed for a long time, and the correlation between the light emitting characteristics of a semiconductor light emitting device and the epitaxial structure, crystallinity, doping characteristics, etc. is investigated. Among them, it has been found that the luminous efficiency of the light emitting device is influenced by impurities not intentionally added, rather than the carrier concentration of the active layer, and thus the quality is not stable.

FIG. 8 shows the structure of the semiconductor light emitting device to be investigated. An n-clad layer 13 made of n-type InGaAlP and an undoped InGaAlP are formed on a semiconductor substrate 12 doped with silicon (Si) at a concentration of about 1 × 10 ¹⁸ / cm ^3.
Active layer 14 made of P, P made of P-type InGaAlP
The clad layer 15 and the current diffusion layer 16 made of P-type AlGaAs are both formed in lattice matching. A first electrode 17 and a second electrode 18 are formed on the current diffusion layer 16 and the substrate 12, respectively. The active layer 14 and the n-clad layer 13 and the p-clad layer 15 that sandwich the active layer 14 from above and below constitute a double heterostructure.

During the development of such a semiconductor light emitting device, the brightness of the semiconductor light emitting device varied, and in some cases, a phenomenon in which no light was emitted occurred. In view of such a problem, as a result of conducting a process history investigation, as shown in FIG. 11, especially when TMA (trimethylgallium) and TMI (trimethylindium), which are the source gases used in the manufacturing process of the semiconductor light emitting device, are replaced, It was found that the luminous efficiency was remarkably varied.

Further, as a result of disassembling and examining the non-defective and defective semiconductor light emitting devices by the SIMS method, as shown in FIG.
Compared to the good semiconductor light emitting device (FIG. 9B), the defective semiconductor light emitting device (FIG. 9A) has AlGaAs and In
It was found that Si and O were mainly mixed in GaAlP as impurities, and the concentration was considerably higher than that of a good semiconductor light emitting device.

Further, in order to investigate whether such a phenomenon is caused by a large change in the carrier concentration of the active layer or whether the impurities determine whether the product is a good product or a defective product, the impurity concentration in the active layer is determined. The correlation between the carrier concentration and the carrier concentration and the luminous efficiency of the semiconductor light emitting device are graphed. The result is shown in FIG. As shown in FIG. 10, it was revealed that the semiconductor light emitting device having a luminous efficiency of 1% or more is dominated by the impurity concentration in InGaAlP.

FIG. 10 shows the carrier of the active layer measured by CV, in which the higher impurity of the oxygen and Si impurities of the active layer obtained by the SMIS analysis of each semiconductor light emitting device is step-etched along the horizontal axis. The concentration is plotted on the vertical axis, and the luminous efficiency of each semiconductor light-emitting device is further classified into 1% or less and 1% or more,
This is a plot of the luminous efficiency. In FIG. 10, it can be clearly seen that the luminous efficiency is lowered in the semiconductor light emitting device under the condition that the carrier concentration of the active layer is about 5 × 10 ¹⁶ cells / cm ³ or less.

As described above, in the double-heterostructure semiconductor light emitting device having the active layer made of InGaAlP, stable emission efficiency cannot be obtained only by controlling the carrier concentration of the active layer, which causes quality problems. There are problems such as reduced productivity.

The present invention has been made in consideration of the above points, and an object thereof is to provide a semiconductor light emitting device having an active layer made of InGaAlP, which can obtain stable light emitting efficiency. And

[0012]

SUMMARY OF THE INVENTION The present invention comprises a semiconductor substrate, a double heterostructure provided on the semiconductor substrate,
The double heterostructure includes a first electrode and a second electrode respectively provided on the semiconductor substrate, and the double heterostructure includes an active layer made of an InGaAlP-based material,
The active layer of the InGaAlP-based material is composed of a pair of cladding layers sandwiching the active layer from both sides, and the element concentrations of oxygen and silicon contained in the active layer of the InGaAlP-based material are 5 × 10 ¹⁶ pieces / cm ^{3 respectively.}
The semiconductor light emitting device is characterized by the following.

[0013]

According to the present invention, the luminous efficiency of the semiconductor light emitting device can be improved in a stable state by setting the residual impurity concentration of the active layer made of InGaAlP-based material to 5 × 10 ¹⁶ parts / cm ³ or less. it can.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 1 to 7 are views showing an embodiment of a semiconductor light emitting device according to the present invention.

The basic structure (layer structure) of the semiconductor light emitting device according to the present invention is substantially the same as that of the conventional device shown in FIG. That is, as shown in FIG. 8, the semiconductor light emitting device has n-Ga
A semiconductor substrate 12 made of As, and an n-clad layer 13 made of n-InGaAlP disposed on the substrate 12.
And an active layer 14 made of undoped InGaAlP
And a P clad layer 15 made of P-InGaAlP,
And a current diffusion layer 16 made of P-AlGaAs.

The first electrode 1 is formed on the current spreading layer 16.
7 is provided, and the second electrode 11 is provided below the substrate 12. Further, the active layer 14 and a pair of clad layers 13 and 1 that sandwich the active layer 14 from above and below.
5 and 5 form a double heterostructure.

Note that, in FIG. 8, a P-GaAs layer may be interposed between the first electrode 17 and the current diffusion layer 16.

In the present invention, in the semiconductor light emitting device having the above structure, in order to suppress variations in quality of the semiconductor light emitting device, defective products are analyzed, raw material gases are analyzed, epitaxial growth parameters are analyzed, and substrate characteristics are analyzed. The identities and conditions of the impurities that control the characteristics were obtained.

As described above, it is known that the luminous efficiency is governed by the oxygen or silicon (Si) concentration rather than the carrier concentration of the active layer (see FIG. 10).

To investigate which impurities are more predominant or have no correlation with luminous efficiency, In
The correlation between Si impurities and oxygen impurities contained in the active layer 14 made of GaAlP was investigated, and the result is shown in FIG. In FIG. 1, oxygen is plotted on the horizontal axis and Si is plotted on the vertical axis, and the luminous efficiency of the semiconductor light emitting device is classified into 1% or less and 1% or more, and the luminous efficiency is plotted. As shown in FIG. 1, Si and oxygen have almost no correlation and are independent of each other.
Also, it can be seen that the semiconductor light emitting device which can be said to be a good product is in the region of 5 × 10 ¹⁶ cells / cm 3 or less in both cases of oxygen and Si.

Next, FIG. 2 shows the relationship between the consumption of the material gas used in the manufacturing process of the semiconductor light emitting device and the amount of mixed impurities. Figure 2 shows trimethylindium (TM
I) The relationship between the consumption rate and the oxygen concentration in InGaAlP was investigated. In FIG. 2, the initial concentration with low consumption is 3.6 × 10 ¹⁶ cells / cm ³ for lot B and 5.3 × 10 ¹⁶ cells / cm ³ for lot A. rare. However, compared with the rod B having 4 × 10 ¹⁶ pieces / cm ³ when consuming about 90% of TMI,
Lot A is 2.5 × 10 ¹⁷ cells / cm ^{3, which} is close to 1 digit, and it has been found that it is necessary to thoroughly examine the raw material gas and obtain a (low impurity) semiconductor light emitting device.

From the above investigation, it was found that the impurities mixed in the active layer independently affect the luminous efficiency, and that there is a difference in the time-dependent change in the amount of raw material gas mixed depending on the lot (including bottle). I found that there was a need for measures.

Next, the correspondence between the amount of mixed impurities and the luminous efficiency was examined, and the conditions were found. First, a semiconductor light emitting device having the structure shown in FIG. 8 was manufactured by the following procedure. Epitaxial growth was performed using a normal MOCVD apparatus and H ₂ flow rate of 10 l.
/ Min Trimethylindium (TMI) 0.5 to 0.
8CCM, trimethylgallium (TMA) 20-400
CCM, A _s H ₃ is 500~800CCM, PH ₃ 250
˜400 CCM was flowed and the substrate was grown at a substrate temperature of 720 to 890 ° C. The N-type layer is 10 to 15 CCM of SiH ₄ , and the P-type layer is D
It was formed by flowing MZ (dimethyl sink) at 0.3 to 0.6 CCM.

Thereafter, the back surface lap and the first and second electrodes 17 and 11 are attached, and after dicing,
A 400 μm square and 200 μm high pellet was prepared and resin-molded to manufacture a semiconductor light emitting device.

Next, the luminous efficiency of the semiconductor light emitting device at the time of energization of I _F = 20 mA (V to 5 V) was determined. In addition, SIMS analysis was performed on a part of the pellets to measure the amounts of impurities and dopants in each layer.

In the above manufacturing process, TM of the raw material gas is used.
As I, its purity is Si by atomic absorption spectrometry,
There were prepared oxygen and heavy metals having detection limits (10 ppm) and impurities in the active layer after epitaxial growth of about 1.5 × 10 ¹⁶ pieces / cm ³ . Furthermore, a small amount of oxygen was introduced into the furnace during the manufacturing process to determine the relationship between the luminous efficiency of the semiconductor light emitting device and the impurities in the active layer,
The conditions under which the efficiency does not drop abnormally are defined and shown in FIGS. 3 and 4.

FIG. 3 and FIG. 4 show that when SiH is grown,
₄ is a plot of the luminous efficiency of a semiconductor light emitting device obtained by independently introducing a small amount of ₄ and oxygen and the respective impurity concentrations of oxygen and Si contained in the active layer made of InGaAlP. As shown in FIGS. 3 and 4, the concentration of both oxygen and Si is 5 × 10 ¹⁶ cells /
Luminous efficiency dropped to 1% or less at cm ³ or more. According to FIGS. 3 and 4, it became clear that 5 × 10 ¹⁶ cells / cm ³ is the threshold value of oxygen and Si at which the luminous efficiency is not significantly lowered.

The residual impurity concentration in the n-clad layer 13 and the p-clad layer 15 is 1 × 10 ¹⁷ pieces / cm ³ or less.

However, the luminous efficiency may be distributed to 1 to 3.5% even below this threshold value, and the following measures were taken against this.

First, the purity of TMA was checked as in the case of TMI, and the relationship between the respective concentrations of oxygen and Si in the current diffusion layer and the luminous efficiency was obtained. At this time, as the TMI, one whose purity has been confirmed is used, and AlGaA forming the current diffusion layer is used.
A small amount of oxygen and Si were mixed only during the s growth. 5 and 6 show the results in this case. The purity of oxygen and Si in the active layer of the semiconductor light emitting device is suppressed to 5 × 10 ¹⁶ or less, and the oxygen contained in the current diffusion layer is 2 ×.
10 ¹⁹ pieces / cm ³ or less, 1 × 10 ^{17 for} Si
When it was set to be not more than K / cm ³ , the luminous efficiency of 1.2 to 3.5% could be surely obtained.

Next, the relationship between the luminous efficiency and the impurity concentration of the active layer when the plane orientation of the semiconductor substrate was changed was examined.

Regarding the plane orientation of the semiconductor substrate, the luminous efficiency and InGaAl were changed by changing the plane orientation of the (100) just that is normally used to 5 ° to 20 ° in the [011] direction.
The relation of impurities contained in the active layer made of P was obtained.
The result is shown in FIG. 7. As shown in FIG. 7, as it turns off from [100] in the (011) direction (as it shifts),
It was found that the luminous efficiency was increased, and at the same time, the amount of oxygen taken into the active layer was decreased. For Si, there was no dependence on changes in the plane direction. It was found that by inclining the plane orientation of the semiconductor substrate from [100] to the (011) direction by 10 to 20 °, it becomes difficult for oxygen to be taken into the active layer, and a semiconductor light emitting device with a luminous efficiency of 1 to 3% can be obtained. It was

It has been found that also in the semiconductor light emitting device having the active layer having the multiple quantum well structure, the threshold value for the luminous efficiency exists with respect to the impurities in the active layer as described above.

In SIMS analysis, the measurement limit is about 1 × 10 ¹⁵ cells / cm ³ , but the above-mentioned increase in luminous efficiency is within the range of 1 × 10 ^{15 to} 5 × 10 ¹⁶ cells / cm ³ . It was noticeable in. In addition to oxygen or Si, Z
Similar threshold values were obtained with respect to luminous efficiency for P-type impurities such as n and Mg or other n-type impurities such as Te.

According to the present embodiment, by controlling the residual impurities in the active layer made of the InGaAlP layer and further the impurities in the current diffusion layer made of AlGaAs, it is possible to reduce the amount of impurities in FIG.
As shown in, extremely stable luminous efficiency was obtained.

[0036]

As described above, according to the present invention,
By setting the residual impurity concentration of the active layer made of the InGaAlP-based material to be 5 × 10 ¹⁶ / cm ³ or less, the luminous efficiency can be improved in a stable state. Therefore, the semiconductor light emitting device does not have problems such as quality troubles and reduction in productivity.

[Brief description of drawings]

FIG. 1 InGaAlP of a semiconductor light emitting device according to the present invention
FIG. 5 is a diagram showing the relationship between the impurity concentration in the active layer made of and the luminous efficiency.

FIG. 2 is a diagram showing a relationship between TMI consumption and oxygen concentration in an active layer.

FIG. 3 is a diagram showing a relationship between oxygen concentration in an active layer and luminous efficiency.

FIG. 4 is a diagram showing the relationship between the Si concentration in the active layer and the luminous efficiency.

FIG. 5 is a diagram showing a relationship between oxygen concentration in a current diffusion layer made of AlGaAs and luminous efficiency.

FIG. 6 is a diagram showing the relationship between the Si concentration in the current diffusion layer and the luminous efficiency.

FIG. 7 shows the off angle of the plane orientation of the semiconductor substrate and the luminous efficiency.
The figure which shows the relationship with an active layer impurity.

FIG. 8 is a diagram showing a basic structure of a semiconductor light emitting device.

9A and 9B are diagrams showing results of detecting matrix elements and impurity concentrations of a semiconductor light emitting device by SIMS.

FIG. 10 is a diagram showing the relationship between the impurity concentration in the active layer, the carrier concentration, and the luminous efficiency.

FIG. 11 is a diagram showing the relationship between TMI consumption and oxygen concentration in the active layer.

[Explanation of symbols]

12 Semiconductor substrate 13 n cladding layer 14 Active layer 15 p clad layer 16 Current spreading layer

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-6-268322 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 33/00

Claims (5)

(57) [Claims] 1. A double hetero structure comprising: a semiconductor substrate; a double hetero structure provided on the semiconductor substrate; and a first electrode and a second electrode provided on the double hetero structure and the semiconductor substrate, respectively. The structure is composed of an active layer made of InGaAlP-based material and a pair of clad layers sandwiching the active layer from both sides. The element concentrations of oxygen and silicon contained in the active layer of the InGaAlP-based material are respectively. A semiconductor light emitting device characterized by being 5 × 10 ¹⁶ cells / cm ³ or less. 2. The semiconductor substrate is made of GaAs, and the plane direction of the semiconductor substrate is 10 from (100) to [011] direction.
The semiconductor light emitting device according to claim 1, wherein the semiconductor light emitting device is inclined at an angle of -20 °. 3. Between the double heterostructure and the first electrode,
A current diffusion layer made of AlGaAs is provided, and the element concentration of oxygen in this current diffusion layer is 2 × 10 ¹⁹ cells / cm ³ or less, and the element concentration of silicon is 1 × 10 ¹⁷ cells / cm ³ or less. The semiconductor light emitting device according to claim 1. 4. The pair of clad layers are made of InGaAlP-based material, and the residual impurity concentration of the pair of clad layers is 1 or less.
2. The method according to claim 1, wherein the density is × 10 ¹⁷ cells / cm ³ or less.
The semiconductor light-emitting device described. 5. The semiconductor light emitting device according to claim 1, wherein the active layer has a multiple quantum well structure.