JPS599984A - Gallium phosphide green light emitting diode - Google Patents

Abstract

PURPOSE:To obtain a green LED having high luminance, by sequentially growing an n<+> layer, an N layer, and a P layer on an N type GaP substrate by an epitaxial method. CONSTITUTION:The impurity concentration of an N layer 2 on a substrate 1 is 8X 10<17>cm<-3>. When its light emitting efficiency reaches about 0.42, it is saturated. Meanwhile, S pits, which are the cause of the saturating phenomenon, are quickly increased to 2-3X10<4>cm<-3>. Therefore, the concentration of the layer 2 is selected to be 5-8X 10<17>cm<-3>, which is higher than that of the substrate 1. When Si is added to S, which is a main donor, by 5-6X10<16>cm<-3>, alignment of the N type substrate and the N<+> layer can be readily obtained. Even though an N layers 3 and 4 are laminated thereon, position inversion is not accured. The layer 3 is provided so that the S is scattered at a high temperature and the concentration is decreased. The N layer 4 is a light emitting layer. When NH3 is not introduced, light emitting efficiency is decreased and moved to the side of a short wavelength. When N is 10<18>-10<19>cm<-3>, and central wavelength is 568nm and the light emitting efficiency is about 0.45%. When the N is about 10<16>cm<-3>, the central wavelength is 556nm and the efficiency is 0.15%. Since the Si does not directly contributes to the light emitting it is desirable to remove it. In this constitution, an LED having high emitting efficiency and a long life can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a high brightness phosphide gallium green light emitting diode (
-Related.

Conventionally, it was known that in order to emit green light with high efficiency in a light-emitting diode using gallium phosphide (or gallium phosphorus 1()aP), it is better to lower the n-layer temperature of the two-Pn junction. For example, Tohoku Review Vol.
] 41Y Two (2) step-like impurity concentration distribution (2) It is reported that a luminous efficiency of around 0.5% was stably obtained. However, such an impurity concentration distribution (
:Then, many of the devices behave in a swivel mode (so-called thyristor behavior), so when we investigated the cause of this through experiments, we found that lowering the concentration of the n-layer near the single-C2 pn junction caused light emission (such as non-contributing currents, etc.). It was found that a large number of impurities (2 being a small number key 9) caused transistor operation, and that it was necessary to grow an n-layer while confirming the crystallinity.

The present invention has been made in consideration of the above-mentioned points, and the present invention will be explained in detail based on two embodiments below.

Figure 2 (al is a schematic diagram of a phosphorized green light emitting diode according to an embodiment of the present invention, and Figure 1k11 is an impurity concentration distribution diagram of the light emitting diode. This is a single crystal sliced from a 3×10” (1)4 n-type substrate manufactured by a pulling method, etc. f2
1f314+ is each 5~8X1017 countries -5.1~
The n layer (epitaxially grown layer) has an impurity concentration of 2X10"-""-1 to 5X10"am-', and the growth thickness is in the order (
: 40 to 50 μm, 115 to 25 μm, and 8 to 14 μm, of which only the outermost D1gJi41 is doped with Nitsuyuki. (5) is a P layer with a thickness of about 25 μ7 and an impurity concentration of 5 to 10×10 17 cm''4.

Such a light emitting diode is grown epitaxially, for example, by bringing a thin melt containing silicon and sulfur into contact with each other on a substrate. That is, the n-layer (2) with a higher impurity concentration than the substrate grows when heated from a high temperature of about 103 [J"C to a low temperature of about 2 to 35 °C/min. After that, it is kept at a constant temperature for 45 to 120 minutes. Then, the temperature is lowered again to grow the next n-layer (3) and held at a constant temperature again.Next, when ammonia gas is introduced and nitrogen is added to the melt, silicon in particular reacts and forms precipitates such as 1315N4. occurs, and the silicon in the melt can be removed to %'.Then, the temperature is lowered again and n7 heads (41) are grown.Therefore, this n layer (4) (2 is heavily doped with nitrogen, but The silicon is only slightly doped, and the P layer (5) is grown within the metal layer (with zinc heat introduced twice).

By soldering in this way, the n-layer (21) with a high impurity concentration affects the crystallinity of the sequentially grown layers, and the dislocation density decreases by holding the temperature at a constant temperature after each n-layer grows. Since there are few impurities other than the nearby C dinitrogen, no switching action occurs.

As described above, the present invention comprises an n-type phosphorous gallium substrate, an n-layer epitaxially grown on the substrate and having an impurity concentration lower than that of the substrate, and a p-layer forming a Pn junction with the n-layer having a lower impurity concentration. Since it is a phosphorized Gadjiwam green light emitting diode with An element with a long life of more than 1 hour (high temperature large-scale flow test) was obtained.

[Brief explanation of drawings]

Figure 1 is a schematic diagram ta+ and an impurity concentration distribution diagram (1)l of a conventional light emitting diode, and Figure 2 is a schematic diagram (&) and an impurity concentration distribution diagram (b ). fl+...Substrate, T2++31+43-n layer, (5
1-P layer. Applicant: Sanyo Tsuboki Co., Ltd. and one other representative: Patent attorney: Makoto Sano Snoring 1'+':'y b;
XN1,Σ'j:ζ];5) Figure 1 (CI) Figure 2 (C1) (b) [CI' Amendment (self-motivated) dated May 1, 1980, Commissioner of the Japan Patent Office1, Indication of the case, Patent Application No. 119208 of 1982, Title of the invention: Gallium phosphide green light emitting diode6, Person making the amendment. Related Patent Applicant 4, Agent Address 2-18-5 Keihan Hondori, Moriguchi City, Specification Subject to Amendment 1, Name of Invention Gallium Phosphide Green Light-Emitting Diode 2, Claims 1 ) An n-type gallium phosphide substrate, an n layer epitaxially grown on the substrate, a substrate with a high concentration of cine particles, an n layer with a low impurity concentration laminated thereon, and an n layer with a low impurity concentration. A gallium phosphide green light emitting diode comprising: and a P layer forming a Pn junction. 3. DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high brightness gallium phosphide green light emitting diode. Conventionally, it has been known that in order to emit green light with high efficiency in a light emitting diode using gallium phosphide (or gallium phosphide: GaP), it is better to lower the n-layer concentration of the Pn junction. For example, according to Tohoku Review Vol. 67, No. 6, p. 567, if the n-layer (13) and (14) are separated into two and made into a stepped impurity concentration distribution as shown in Figure 1, the luminous efficiency will be around 0.6%. It is reported to be stable. However, with this type of impurity concentration distribution, many devices perform a switch operation (so-called transistor or silice operation), and when we investigated the cause of this through experiments, we found that it was simply by lowering the concentration of the n layer near the Pn junction. In this case, a P-inverted portion occurs in the n-layer, and therefore a nun or nPnP region is formed to cause a switching operation, and there are also many buybacks that do not contribute to light emission. The present invention was made in consideration of the above-mentioned points, and focused particularly on the need to grow the n-layer while confirming the crystallinity of the substrate and the growth layer. This will be explained in detail based on the following. FIG. 2(a) is a schematic diagram of a gallium phosphide green light-emitting diode according to an embodiment of the present invention, and FIG. 2(b) is an impurity concentration distribution diagram of the light-emitting diode. In the figure, (1) is a slice of a single crystal produced by a pulling method etc. on an n-type substrate with a fines concentration of 1 to 10 CI11.
-3 16 -310CM,
N layer (epitaxially grown layer) with an impurity concentration of 0.6 to 3 × 103, the growth thickness is 40 to 50 μm, 1
5 to 25 μm, 8 to 14 μm, among which the tension n layer (
Only 4) is doped with nitrogen. (5) is a P layer with a thickness of about 25 μm and an impurity concentration of 5 to 10×10×10 17 . Such a light emitting diode, for example, is grown epitaxially as follows by contacting a thin melt layer containing silicon and sulfur on a substrate. That is, when the temperature is lowered from a high temperature of about 1030''C at a low rate of about 2 to 6.5°C/min, an n-layer (2) with a higher impurity concentration than the substrate grows.Then, the temperature is kept at a constant temperature for 45 to 120 minutes. Then the temperature decreases again and the next n
F! (3) is grown and held at a constant temperature again. Then, when ammonia gas is introduced and nitrogen is added to the melt,
In particular, silicon reacts to produce precipitates such as 5iaN4,
The silicon in the melt 1 can be removed quickly. Thereafter, the temperature is lowered 10 times to grow an n-layer (4). Therefore, this n layer (
4) is heavily doped with nitrogen but only slightly with silicon. Next, zinc is introduced into the melt to grow the P layer (5). Of the light emitting diodes manufactured in this way, the n-layer (2) (31 (41) will be explained in detail. When the value of 1017, -3, the luminous efficiency is about 0065%, but as the impurity concentration increases, the luminous efficiency also increases, and becomes 8×1.
At 0 cPIi, it is about 0.42%. However, after that, the luminous efficiency shows a saturation phenomenon. On the other hand, the S pit, which is an impurity bit, is approximately 1Qx-2 below 5X1017m-3.
However, as the impurity concentration increases, it increases to 10 cN.
Then, it becomes 2~3×100. The above-mentioned saturation phenomenon of luminous efficiency with increase in impurity concentration is considered to be due to the rapid increase in the number of 8 pits. Therefore, the impurity concentration of this n-layer (2) is preferably 6 to 10×10 cm, which is higher than that of the n-type substrate (1), and most preferably 5 to 8×10 cm. This value is also confirmed by observing the etched surface of the light emitting diode with eight microscopic lenses. That is, the etch rate during etching differs at the junction between crystal planes, and if the crystals are poorly matched, black lines appear. When fluoronitric acid is used as an etchant, the impurity concentration of the n-layer (2) is 1
[If the value is about 117z-3 or less, it is determined that matching is achieved when the value is 17CI11-3. As a result of extensive experiments, matching is easily achieved when sulfur is used as the main donor impurity and silicon is added in a small amount of 5 to 6×10 16 ar 3 . Next, the n-layers (3) (4+) are layers formed on the fcn layer (2) that are not matched with the n-type substrate mentioned above.
P inversion did not occur even at low concentrations. The n-layer (3) is for scattering sulfur into the atmosphere at a relatively high temperature to reduce its concentration, and the n-layer (4) is effectively a light-emitting layer. Without the introduction of ammonia, the luminous efficiency decreases, but the luminous wavelength shifts to the shorter wavelength side. When the amount of nitrogen doped is 1018 to 1019G-3, a luminous efficiency of about 0.45% with a center wavelength of 568 nm can be obtained, and l'Q 16 cm-3 without active doping.
When it is about 5560m, it becomes 0.15%. In any case, silicon does not directly contribute to light emission, so it is better to remove it. As described above, the present invention comprises an n-type gallium phosphide substrate, an n-layer epitaxially grown on the substrate and having a higher impurity concentration than the substrate, and a p-layer forming a Pn junction with the n-layer having a lower impurity concentration. Since it is a gallium phosphide green light-emitting diode, it can achieve a luminous efficiency of 0.45%, which is much higher than conventional methods (0.2% to 0.6%), and it takes more than 1500 hours to reduce the brightness by 80%. (High temperature high current test)
A long-life device was obtained. 4. Brief explanation of the drawings Fig. 1 is a schematic diagram (a) and an impurity concentration distribution diagram (b) of a conventional light emitting diode, and Fig. 2 is a schematic diagram (a) of a potassium phosphide green light emitting diode according to an embodiment of the present invention. ) and impurity concentration distribution diagram (I)) 7, (1)...Substrate, (2+(3) (4)...
...n layer, (5)...P layer. Applicant Sanyo Den+; tt +'+: Shikisha IT:ill
Gai 1z Soku Tosano Shizuo 386

Claims (1)

[Claims] 1) An n-type hygallium substrate, an n-layer with a higher impurity concentration than the substrate that was grown epitaxially on the substrate, and a laminated impurity (low-quality n-layer and its impurity concentration) A light-emitting diode made of phosphide galliwaum green f!!, characterized in that it comprises an n-layer with a low temperature and two layers forming a p-n junction.