JPS63314875A - Light emitting diode chip structure - Google Patents

Abstract

PURPOSE:To reduce the content of aluminum as much as possible and to enhance durability without varying an emitting light intensity by reducing the x value of a Ga1-xAlxAs light confinement layer to a predetermined value or smaller. CONSTITUTION:An LED 10 is formed as a laminated structure of a p-type Ga1-xAlxAs (x=0.7 or less) as a light confinement layer 12, a p-type Ga1-xAlxAs (x=0.35) as a light emitting layer 13 laminated thereon, and an n-type Ga1-xAlxAs (x=0.7 or smaller) as a light confinement layer 14 laminated on the layer 13, and a p-n junction is formed between the layers 13 and 14. An LED 10 is covered with a protective film 15 formed of an oxide film on the whole periphery except metal electrodes 16, 17, and a reflection of the light from a crystal end is regulated. The content of the aluminum is set to x=0.7 to obtain its durability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of a light emitting diode chip, particularly a GaAlAs double heterojunction light emitting diode chip.

・[Prior art and problems] In recent years, the luminous efficiency of light emitting diodes (hereinafter abbreviated as LEDs) has significantly improved, and for example, LEDs with a pn junction structure using m-v group compound semiconductors have It is widely used in display devices for symbols, etc., and is also being put into practical use as a light source for optical communications and a light source for illumination.

The material for such LEDs is generally 1n+-xGa.
, p, Ga+-xAl, w^Sv In+-x G
ag AS+-y Using mixed crystals of different types of m-v group compound semiconductors such as Py, by changing the component ratio (X or y value), crystal layers with different forbidden band widths and refractive indexes are stacked, so-called. LEDs configured with a double heterojunction are known.

By forming such a double heterojunction,
LEDs now have a carrier confinement function and a light confinement function, and various performances such as luminous efficiency, luminous intensity, and luminous wavelength are significantly improved. Among them, Ga1-xAll
LEDs using As crystals emit red light in the visible range (approximately 6
LEDs are in great demand because they emit light in a wide wavelength range from around 50nm to the infrared region of about 900r+s.
It is attracting attention as

Visible range with conventional double heterostructure (approximately 650 to 6
70n+m) Ga1-, ^1. AsLED is the third
As shown in the figure, mainly p-type Ga+ of the substrate that becomes the light-transmitting layer
-xAlx AsJli 1 (component ratio is usually x-
0,65), p-type Ga+-X which becomes an optical confinement layer
AIX As layer 2 (x = 0.8) is laminated by liquid phase growth, etc., and on top of that is a p layer that becomes a light emitting layer called an active layer.
Type GaAlAs, As layer 3 (x = 0.35)
and further form a pn junction on top of it,
n-type Ga+-, Alx As layer 4 as an optical confinement layer
(x = 0.8) is grown in layers to form an LED. Metal electrodes 6 and 7 for ohmic contact are formed on the light emitting surface and the back surface of the LED. Furthermore, the entire periphery of the crystal except for these two electrodes 6 and 7 is covered with a protective film 5 formed of an oxide film, etc., which protects the LED from moisture etc. and also reflects light from the crystal edges. It is now possible to adjust the

The composition ratio of gallium (Ga) and aluminum (AI) (that is, the value of This is to improve the performance such as the luminous efficiency of the
And 4 is! -0.8, the content rate of AI is set high.

However, in conventional LEDs with such a high AI content, the following problems have arisen because ^l is active or easily oxidized.

In other words, the light confinement layers 2 and 4 have a high ^l mixed crystal ratio, so they have high hygroscopicity, and by adsorbing moisture, light absorption layers are easily generated on the front and back surfaces of the layers, which absorb light and cause the LED to emit light. The strength often decreased over time. In order to prevent such a reduction in luminous intensity, a protective film 5 such as an oxide film is formed to seal the entire area except for the 8i 6.7, but this is not sufficient in terms of moisture proofing and causes a decline in the performance of the LED. It was inevitable. Also, At
Due to the high content of the optical confinement layer 4, the surface of the optical confinement layer 4 is easily oxidized, and it is difficult to make ohmic contact with the electrode 7, resulting in a decrease in yield.

[Purpose of the invention]

In view of the above points, it is an object of the present invention to provide a Gap-Jlw AsL ED with almost no change in emission intensity and high durability by reducing the aluminum content as much as possible.

[Means and effects for solving the problem] According to the present invention, the above object is achieved by forming a G
a, □A1. This is achieved by a double heterojunction light emitting diode chip in which the As optical confinement layer has an X value of x=0.7 or less, preferably x-0.65 or less.

According to this invention, optical confinement rMGap-Jim A
Since the X value of s is reduced, the rate of decrease in initial luminous intensity is suppressed even when the LED is used in high temperature conditions, and ohmic contact is improved.

〔Example〕

Hereinafter, the present invention will be further explained with reference to FIG. 1, which shows a cross-sectional example of a GaAlAs LED obtained according to the present invention.

LEDIO uses p-type Ga as optical confinement l112
p-xAlx As (x-0.7 or less) and p-type Ga+-Jlx A as the light emitting layer 13 laminated thereon
s (x −0,35), and n-type Ga+− as the optical confinement layer 14 layered on the light emitting layer 11113,
It is made of a laminated structure of AlxAs (x = 0.7 or less), and a pn junction is formed between the p-type light emitting layer 13 and the n-type confinement layer 14. 16.17 is LE
These are metal electrodes for ohmic contact formed on the light emitting surface and back surface of the DIO.

Furthermore, the LEDIO of this embodiment has both the electrodes 16°1
The entire surrounding area except for the part 7 is covered with a protective film 15 formed of an oxide film, etc., and the LE is protected from external moisture.
It protects the DIO and adjusts the reflection of light from the crystal edges.

Here, since the emission wavelength of LEDlo is mainly influenced by the forbidden band width of the light emission 7113, the amount of ^l of the light emitting layer 13 is designed and set according to the purpose of use. When LEDlo emits light in the visible range, the ratio of 1 to 1 is! = about 0.35, and when emitting light in the infrared region, the A1 ratio of the light emitting layer 13 can be further lowered, so that almost no light absorption layer is generated in the light emitting layer 13.

Therefore, when forming the optical confinement layers 12 and 14, the question is how much the forbidden band width should be widened and the refractive index should be changed compared to the above-mentioned light emitting layer 13. In the past, due to the initial performance concerns, an optical confinement layer containing a higher proportion of AI than necessary was formed, resulting in the above-mentioned problems.

The present inventors have repeatedly conducted various experiments on LED performance, temporal changes in light intensity, and yield while gradually lowering the AI content of the optical confinement layer 12.14 from the conventional value, and have determined the optimal AI content. I found out.

That is, the content of AI in the optical confinement layer (AI relative to Ga)
It has been found that the object of the present invention can be achieved by setting the composition ratio (x=o) to 7 or less.

Now, ^l of pH 12 and 1 layer 14, which will become the optical confinement layer.
Let the content rate of x=0.65, Gas, 3sA1*,
An LED using a crystal layer made of 6SA3 was fabricated, and the temporal change in luminescence intensity was measured in an operating state (forward current Iv = 30 taA) at a high temperature (85°C) and high temperature (RH = 85%) when the AI ratio was 0. Conventional Gats, which is as high as .8,
xAle, *LED with As optical confinement layers 2, 4
compared with. At that time, 25 pieces each were manufactured, one with a protective film formed thereon and one without it.

The results are shown in FIG. In the figure, A is an LED according to the present invention with a protective film formed thereon, the opening is a glue without a protective film according to the present invention, ED, and C is a conventional LED with a protective film formed thereon.
The second is a conventional LED without a protective film.

As is clear from this figure, the LED according to the present invention is
Not only does the absolute value of the emitted light intensity remain the same compared to conventional LEDs, but even after 500 hours of operation time, the intensity changes are much smaller than with conventional LEDs. It can be seen that the light emission intensity of the LED port of the invention did not decrease much.

Furthermore, what is the AI content of the optical confinement layer 12.14? -0.7
There is no practical problem if it is below, but! =0.65 or less is optimal.

In this way, the light confinement layers 12 and 1 sandwich the light emitting layer 13.
The content of AI in No. 4 is set to X = 0.7 or less, preferably X = 0.
．． By setting the AI content to 65 or less, the temporal decrease in emission intensity can be minimized, but to explain how much this AI content can be reduced, it is necessary to The purpose of this is to make the forbidden band width wider and the refractive index smaller than that of the light emitting layer 13 in order to confine carriers in the light emitting layer. Therefore, the AI content of the optical confinement layer should be determined within that range, and in any case, x = 0.7, preferably x - 0.65 or less. It's good. Therefore, the present invention is an LED in the infrared region.
Of course, it can also be applied to

According to the present invention, it is possible to lower the AI content of the p-type light confinement layer 12, so that the p-type light transmitting layer 1, which is a substrate formed in a conventional LED, and the above-mentioned light confinement layer 12 according to the present invention The AI content is the same as that of the p-type optical confinement layer 12, and as a result, the two layers can be grown simultaneously under the same manufacturing conditions. Therefore, the number of growth materials, jigs, manufacturing steps, etc. can be reduced.

〔Effect of the invention〕

As described above, according to the present invention, the
-0.7, preferably x-0.65 or less, the lower AI content makes it difficult for the surface of the crystal layer to oxidize (which makes it easier to form ohmic contact electrodes, resulting in lower yields). improves.

Furthermore, the stability against moisture is improved and the formation of a light absorption layer can be prevented. Therefore, the luminous intensity does not change for a long time even in a harsh operating environment of high temperature and high humidity, so that the display device using this LED has enough reliability to withstand outdoor use, such as when mounted on a vehicle or the like.

Furthermore, according to the present invention, sufficient quality can be ensured without forming a protective film around the LED, so manufacturing costs can be reduced, and by providing the above protective film, temporal changes in emission intensity can be reduced. It can be made smaller and reliability can be further increased.

[Brief explanation of the drawing]

FIG. 1 is a side cross-sectional view of the GaAlAs L E D according to the present invention, and FIG. 2 shows the temporal change in emission intensity of the GaAlAs L E D according to the present invention compared to that of the conventional GaAlAs L E D.
This is a graph compared with D. FIG. 3 is a side sectional view of a conventional GaAlAs LED. 10-- GaAlAs LED; 12--
-p-type Gap-++AIx As optical confinement Iti;
13-p-type Ga1-, A1. As light emitting layer; 14-
- n-type Gap-XAim As optical confinement layer; 1
5.--Protective film i 16.17--Electrode. Patent applicant: Stanley Electric Co., Ltd. Representative: Patent attorney Hirayama - Distance: Patent attorney Tamotsu Kaizu Figure 1b Figure 2

Claims (2)

[Claims] (1) GaAlAs light emitting layer is Ga_1_-_xAl_x
GaA sandwiched from above and below by As optical confinement layers
In the lAs double heterojunction light emitting diode, the Ga_1_-_xAl_xAs optical confinement layer has an x value of x=0.7 or less.
Light emitting diode chip structure. (2) The GaAlAs according to claim 1, wherein the entire circumference of the GaAlAs light emitting diode except for the electrodes is covered with a protective film such as an oxide film.
s Light emitting diode chip structure.