JPS584987A - Semiconductor light-emitting device and its manufacture - Google Patents

Abstract

PURPOSE:To obtain the LED, luminous color therefrom is completely green and luminous power conversion efficiency thereof is high, by using a GaAlP crystal as the mixed crystal of a Gap crystal and an AlP crystal as the P-N junction forming material of the LED. CONSTITUTION:An N type GaPAlP crystal growing layer 3' and the P type GaAlP crystal growing layer 2' are shaped onto an N type GaP crystal substrate 4. An electrode 5 as a cathode and an electrode 1 as an anode are attached. Since the forbidden band width of the AlP crystal is wider than that of the GaP crystal, the forbidden band width of the Ga1-xAlxP crystal as the mixed crystal is wider than that of the GaP crystal, and approaches to the forbidden band width of the AlP crystal when the ratio of components x is increased. Accordingly, the luminous wavelength of the LED can be brought to a deep green band by properly selecting the value of x.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a display device using a light emitting diode, and in particular to a display device using a green light emitting diode.As is well known, a light emitting diode forms a pn* junction in a semiconductor crystal, and It emits light by applying a forward voltage, and the emission wavelength is determined by K, such as the forbidden band width of the semiconductor material used, the type of impurity, and the difference in the recombination process. Among these, a light emitting diode that is generally known as a light emitting diode that emits green light is a diode that uses GaP as a semiconductor material and nitrogen as an added impurity. The structure of this green light emitting diode will be briefly explained.

FIG. 1 is an example of a cross-sectional view of a conventional green light emitting diode. That is, a pn junction is formed by growing an n-type GaP growth layer 3 and a p-type GaP growth layer 2 on an n-type GaP crystal substrate 4 by J-growth such as liquid phase growth. An electrode 1 as an anode and an electrode 5 as a cathode are attached to this.

Problems and drawbacks in the emission wavelength characteristics of a conventional green light emitting diode using a GaP crystal will be described below.

The first problem is the size of the forbidden band width of the GaP crystal. A material with a larger forbidden band width can shorten the emission wavelength of a light emitting diode. The forbidden band width of GaP crystal is approximately 2.26
eV, so if a light emitting diode was manufactured using this as a pn junction forming material, the light would be emitted at a shorter wavelength than the absorption edge wavelength, that is, from approximately 555 nm, which is on the longer wavelength side in the edge color band. However, it is not possible to obtain light emission at short wavelengths. Therefore, even if this green light emission at approximately 555 rfm can be observed, the luminous efficiency is extremely low and cannot reach a practical value.

The second problem is the wavelength component of the emission wavelength and efficiency. As mentioned above, the luminous efficiency of green light is too low, so in order to increase the efficiency, nitrogen as an impurity is generally added to the NFI/p-type growth layer. When this nitrogen is added, nitrogen (6) can be used as the emission center, so relatively efficient light emission can be obtained, but the emission wavelength is longer than the absorption edge wavelength of about 555 nm. The color shifts toward the wavelength side, resulting in a green color that contains a considerable amount of yellow, rather than approximately. As described above, even in light emitting diodes using Gap crystals, which are most commonly put into practical use as green diodes, it has not been possible to emit light of a completely green color and with high efficiency.

An object of the present invention is to provide a light emitting diode that emits completely green (dark green) and has high luminous efficiency, or a display device using the same.

The present invention is characterized in that a GaAtP crystal, which is a mixed crystal of a GaP crystal and an AtP crystal having a wider forbidden band width than an AAP crystal (3.1 eV forbidden band width), is used as a pn junction forming material for a light emitting diode. However, the details thereof will be explained by the following examples including the manufacturing method.

FIG. 2 shows an example of the structure of a light emitting diode according to the present invention.

That is, an n-type GaAtP crystal growth layer 3' and a p-type GaAAP crystal are grown on an n-type GaP crystal substrate 4 by one liquid phase growth method.
The crystal growth layer 2' is formed and the pn junction forming material is GaAAP crystal. and electrode 5 as a cathode
and an electrode 1 as an anode is attached.

As mentioned above, the forbidden band width of the Mutp crystal is wider than that of the GaP crystal, so Ga 1-X A-11 as a mixed crystal
The forbidden band width of the P crystal is wider than that of the G1P crystal, and as the component ratio X is increased, the forbidden band width becomes closer to that of the KtP crystal. Therefore, it is considered that by appropriately selecting the value of X, the emission wavelength of the light emitting diode can be made into the desired deep fringe color band.

The details of its manufacturing method are described below.

First, n-type Ga, -xIU is deposited on an n-type GaP single crystal substrate.
,,P crystal is obtained by liquid phase growth method, but in order not to change the composition/common ratio
A liquid phase growth method called a temperature drop method is inappropriate, and a liquid phase growth method using a temperature difference method is better. Melt (solvent/solute in liquid phase growth) used in liquid phase growth using this temperature difference method
are Ga, At, GaP, impurities that determine the conductivity type, etc., but the addition of nitrogen to increase the luminous efficiency is
KNH is added in hydrogen gas by mixing the gas and growing the mixture in a liquid phase while flowing the mixed gas.

Figure II3 is an experimental result showing the change in the emission peak wavelength λ (nm) when the component ratio I of the ijn-type and p-type Ga1-XALxP growth layers is changed. In this figure, the solid line is when the atmospheric gas during liquid phase growth is H gas (no nitrogen addition).
The dotted line shows the results when the atmospheric gas during liquid phase growth was a mixed gas of H8 and NH (mixture ratio NH,/H, = 0.004 in this case) (with nitrogen addition).

As this result shows, [, pn junction constituent material is Ga,
-, Aj, and P crystals, the emission peak wavelength could be shifted from about 555 nm to the shorter wavelength side, and the emission wavelength could be completely set in the green wavelength band. Also nitrogen (goods)
The addition of impurities has the same effect as that in conventional GaP crystal light-emitting diodes, and the light emission peak wavelength of the light-emitting diode of the present invention doped with nitrogen is about 2 to 4 times higher than that of the light-emitting diode without nitrogen addition. nm It is moving to the long wavelength side. The degree of this movement is determined by the amount of nitrogen added.

In this way, the K 2 Ga, xALxP crystal also emits light through the same recombination process as in the case of the GaP crystal, and it is thought that nitrogen (he) contributes as a luminescent center, resulting in improved luminous efficiency.

Figure 4 shows an example of the results. In other words, the component ratio X is X=0
．． This figure shows the distribution of external quantum efficiency values when a light emitting diode is cut out from Ueno-- grown at a constant value of 0.06. The solid line #i is the case without the addition of nitrogen, and the dotted line is the case with the addition of nitrogen.

As can be seen from the peak of the distribution, the external quantum efficiency is improved by approximately twice by adding nitrogen.

The conditions for obtaining the results shown in FIGS. 3 and 4 above are as follows.

Growth source 9 degrees is 910 degrees Celsius, temperature difference between source part and growth part is 5
℃, component ratio x t x = 0.2, the composition ratio of the melt material is Ga: AA: GaP = 90: 0
．． 09:2 with ib, the thickness of the n-type Ga1-xAtxP growth layer is approximately 100-120 μm%pm Ga1-XA
The thickness of the P growth layer is approximately 70 to 90 μm. Makun
The type impurity was 8, and the p-deaf impurity #iZn was used.

H supplied as atmospheric gas when adding nitrogen toughness
The mixing ratio of 7 and NH gas is dish, /H, = 0.003 to 0.
It is 004.

Next, in order to obtain a diode of the present invention that efficiently emits light completely in the green wavelength region with even higher performance, the following considerations should be made.

When the ratio of NH,/H was N)Iv/H≦0.002, sufficient nitrogen was not added to the growth layer, and therefore the luminous efficiency was hardly improved. Conversely, Nu(,/H1≧0.
At the time of 005, the carbon jig used in the temperature difference liquid phase growth method reacts with the glass and the gas, so the growth substrate is moved and the p-type Ga1 is deposited on the n-type Ga1-xjuxP growth layer.
It is difficult to adopt a continuous growth method such as obtaining a -xAAxP growth layer. Therefore, NH,/mixed crystal Ga, -
Changing the component ratio X of the xALxP crystal can be achieved by changing the composition ratio in the melt, but as shown in Figure 5, an example of the experimental results, as the component ratio X increases, the external quantum efficiency decreases. It was discovered that this could be done. This is based on the lattice constant of the n-type GaP substrate used during growth and the growth layer Ga 1-x A
If the strain caused by the different lattice constants of the txP crystal or the difference in thermal expansion coefficient during cooling after growth remains in the pn junction or causes defects, the luminous efficiency will decrease due to K. GaP
When a crystal is used as a substrate, the component ratio X is preferably 03 or less.

In addition, based on the same idea, if the thickness of the first n-type Ga, The thicker the better, as it will affect the parts of the body. When the component ratio X of the first growth layer is X=Q, 05, this n-type Ga...@kt6. @ @ Figure 6 shows an example of the results of measuring the external quantum efficiency while increasing the thickness of the growth layer of the P crystal. As can be seen from the figure, Ga, -xA
It is sufficient that the txP growth thickness is about 50-m or more.

The gist of the present invention is that an n-type GaP crystal is used as a substrate and an n
type GaAtP, followed by p-type GaAtP tlj
, the manufacturing method for obtaining a long layer has been described by way of example.
It will be understood that there is no problem in using a manufacturing method that subsequently obtains an n-type GaAAP growth layer.

In addition, in the example, n-type Ga in the P11 junction constituent region, -
, MXP growth layer p-type Ga, -, ALP growth layer with the same component ratio Ga 1-y to increase efficiency
Needless to say, a double heterojunction such as a combination of an AtyP growth layer and a Ga1-, kl, or P growth layer may also be used. Further, although it is more efficient to add nitrogen to both growth layers, it may be added to either one of the growth layers in some cases.

Atmosphere gas is dH, gas (or NH).

Although a mixture of gases) is used, any inert gas may be used, such as Ar gas, N gas, or other gases.

The present invention has been explained as a method for obtaining Ga At P crystals by temperature difference liquid phase growth method. ) A temperature difference liquid phase growth method using so-called vapor pressure control is far more effective.

As described above, by changing the component ratio X of the Ga, -xAj, and P crystals according to the present invention, and by adding nitrogen, it is possible to obtain a deep green color with high efficiency. For example, it is possible to obtain a light emitting diode whose emission peak wavelength can be arbitrarily selected from about 555 nm to 540 nm (a value of 538 am including those without nitrogen added).

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a conventional green diode. FIG. 2 is a cross-sectional view of a green diode according to the invention. FIG. 3 is a graph showing the relationship between the component ratio X and the emission peak wavelength in a green light emitting diode using the G111-X ALxP crystal according to the present invention. FIG. 4 is a graph representing the distribution of external quantum efficiency within a wafer of a green diode according to the present invention. FIG. 5 is a graph showing the relationship between the component ratio @IP
It is a graph showing the relationship between the thickness of the first growth layer and the external quantum efficiency in a green light emitting diode using a crystal. 1.5... Electrode; 21, 31... Crystal growth layer: 4... Crystal substrate. Patent application/Person: Stanley Electric Co., Ltd. Agent: Yasushi Kaizu, Patent Attorney: Patent Attorney Hirayama ) April 16, 1931, Haruki Hatada, Commissioner of the Japan Patent Office, 1, Indication of the incident, 1986 Patent Application No. 10 Yuki No. 814, 2 m110
48 Tei conductor - Party equipment and its manufacturing method Iron 3 Person making the amendment Relationship to the case Address of applicant Address Tokyo - Mushi-ku Nakaichiboku Reicho - No. 9 IS Name Mooring (S80) Stary Denki Xushikikinsha 4, Agent 8 Contents of amendment (1) In 11111, to revise Annex O Haruken of Hall 4-9, -Wall ()l Brass Mura-Xi (No. 4-
) 1 Brass 14 Figure Patent applicant: Stanley Electric Co., Ltd.

Claims (9)

[Claims] (1) GaP crystal plate substrate, G grown on it
a I −x Atxp intracrystalline Kpn! 1. A semiconductor light-emitting device characterized by a semiconductor light-emitting device having an I-contact formed therein. (2) The semiconductor light emitting device according to claim 1, wherein nitrogen is added to the NLL region or at least one region of the NLL region of the Ga□-M txp crystal. . (3) The semiconductor light emitting device according to claim 1, wherein the component ratio X of the grown Ga 1-1kLzP crystal is different between the nfli region and the p-type region. (4) pm of the grown nine Ga 1 +XAtxP crystals! 2. The semiconductor light emitting device according to claim 1, wherein the impurity is zinc and the n-type impurity is sulfur. (5) A method for manufacturing a semiconductor light emitting device, which comprises using a GaP crystal as a substrate and growing a Ga5-xA4P crystal thereon by temperature difference liquid phase growth to form a pn junction. (6) The method for manufacturing a semiconductor light emitting device according to claim 5, wherein the temperature difference method liquid phase growth is performed under phosphorus vapor pressure control. (7) The method for manufacturing a semiconductor light emitting device according to claim 5, wherein the component ratio X of the grown Ga, AA, and P crystals is different between the nll region and the p-type region. (8) nl of the grown Ga, -xjktxP crystal
A method of manufacturing a semiconductor light emitting device according to claim S'lXK, characterized in that nitrogen is added to at least one of the l region and the p type region. (9) The semiconductor light emitting device according to claim 8, wherein the addition of nitrogen is performed by a separating gas, and the content of the gas to the carrier gas is less than or equal to O-S. Production method.