JPS5944878A - Semiconductor light emitting diode - Google Patents

Abstract

PURPOSE:To remarkably improve the linearity of a current-optical output property by a method wherein the sectional area in the direction horizontal to the main surface of the substrate of a conductivity type semiconductor layer is more increased as it is close to an active layer. CONSTITUTION:The region of current flow in a P type clad layer 11 is strictured by a region 13 surrounded by an N type or high resistant semiconductor layer 12. The diameter of the stricture region 13 is more increased as it is closer to the active layer 15 from the point D1 nearest to a P-electrode 14. When current is made to flow from the P-electrode 14, the expansion of the current more enlarges as it is closer to the active layer 15. The expansion of the current becomes larger as the current value is smaller. The variation of this current expansion increases more remarkably than conventional, therefore the change of the luminous diameter compared with current further increases more than conventional.

Description

[Detailed Description of the Invention] The present invention relates to a semiconductor light emitting diode (hereinafter referred to as IJD).
It is related to.

LEDs are important as light sources for optical communication systems, and are being actively researched and developed. Especially the emission wavelength is 0.8
1tm band Gaks/AlGaAs IJDs have already been put into practical use. By the way, the advantages of LED as a light source for optical communication are that it is inexpensive, has high reliability, and has the advantage of having a pure current-butt1 output characteristic. It plays an important role as a light source in the I-2 communication system. Now, as optical fibers have become lower in loss in recent years, '/1 wavelength wavelength 1 control has become in the <21 region where the transmission loss is minimum. In addition to this (i'), InGa, which outputs light in this wavelength range, can also be used as a light source.
Research and development of AsP/InP-based LEDs is progressing. However, in the conventional InGaAsP/InP LED, as the current increases, the light output decreases i't
1! The sum of the 5 forces (a phase phenomenon is observed, current - light 11
The linearity of the 1st force and 4th direction was extremely poor. Unfortunately, the great advantages of LEDs have been lost in the implementation of analog RFF modulation-based T1 systems.

By the way, a recent 6-year study conducted by the present inventors revealed that the saturation of this current-light output characteristic is caused by a light emission current component proportional to approximately the square of the carriers injected into the InGaA,P active layer +QUn. This is because there is a non-luminescent current component proportional to the third power of n, and as the current increases, the proportion of this non-luminescent current component to the total current increases. It has become clear that the possibility of Auger-C coupling is the highest (at N4).Based on the research results of K-Konoshira et al., the thickness of the active layer can be increased in order to reduce the saturation of the current-light output characteristics. A possible solution is to operate with a low concentration of injected carriers by increasing the thickness or by increasing the light emitting area. In fact, the thicker the active layer and the larger the light emitting area, the better the saturation to some extent. However, if the active layer is made thicker than 2 to 3 μm, light absorption increases within the active layer and the injected carriers increase. The distribution in the thickness direction in the active layer becomes non-uniform, leading to problems such as loss of optical output. 1
However, it has been extremely difficult to significantly improve saturation by increasing the thickness of the active layer. Regarding increasing the light emitting area, in order to significantly improve light absorption and phase separation of injected carriers, it is necessary to make the light emitting area extremely large. several tens of microns
There was a problem that when coupled to an optical fiber of about m length, the coupling loss would increase and the fiber/r fiber coupling power would be significantly impaired.

Furthermore, such intra-Auger coupling is possible in InGaAsP
Not only that, but also other semiconductor phase materials that can be used as a light source with a wavelength of 1 to 1.7 μm have the same or higher occurrence of ω1 than InGaAsP, and it is difficult to solve the problem by changing the conductor layer. It is.

In this way, no practical measures have been taken to date to deal with the problem of saturation of current-light output characteristics.

The present invention has been devised to overcome these drawbacks, and provides an IJI with significantly improved precision in current-optical output characteristics without significantly impairing fiber-coupled power. ·be.

That is, it has the light-emitting quardotful structure of the present invention (27, a semiconductor substrate has a semiconductor substrate with a
In a planar light emitting type semiconductor light emitting diode that extracts light in the i direction, a first conductivity type semiconductor layer is provided between the active layer and the first conductivity type Oiy current. This is a semiconductor light-emitting tie-out characterized in that the cross-sectional area in the horizontal direction relative to the main surface of the semiconductor substrate of the side/body layer is increased as it approaches the active layer.

The present invention will be explained in detail below using the drawings.

FIG. 1 is a diagram for explaining the principle of LIID of the present invention. FIGS. 1(a) and 1(b) partially omit the cross sections of J and 18D of the present invention, respectively, compared to the conventional structure. The region where the current rA in the p-type layer 11 flows is the n-type or IJ
j11 resistance semiconductor 1fi12 l! t1 rare'I
It is narrower than the iI region 131C. In the conventional LliiD, this electric current p and the constriction region 13 are formed in a cylindrical shape, as shown in FIG. , p, and s14 are almost the same from 19((D,) closest to the active layer 15 to the location (lJt) closest to the active layer 15, that is, Dt=D2- (and r&).

On the contrary, the LT (D) of the present invention is designed to control the current spread while controlling the current spread, so that the diameter of the constriction region 13 is 1 increases as it approaches the active layer 15 from the point (D) closest to 14. When a current is passed from the p rectangle 14, the spread of the current becomes larger as it approaches the active layer 15, and the spread of the current becomes larger as the current value becomes smaller. When LEDK current is applied, 11. The current spread is large and the current constriction region J 13 hj
The area near the i-type layer 'T: is restricted, as the 1C current increases, the current spread is
7% 7: 1l-j+1.J, the current spread becomes smaller.This change in current spread becomes significantly larger than in the past, and the emission diameter increases. The change with respect to the current is shown in Figure 2, which is much larger on the 4th side than in the case of the /l comb.

By the way, when an LED is coupled to an optical fiber, the coupling efficiency is approximately equal to the inverse ratio of the square of the emission diameter, and becomes larger as the emission diameter becomes smaller. Therefore, as shown in Figure 2,
In the case of the present invention (LE1) in which the emission diameter becomes significantly smaller by α1 when the current is increased by fK x jL, the coupling efficiency becomes significantly larger by [7] as the current increases. Therefore, the fiber-coupled power saturates significantly as the current increases in conventional IJDs, whereas the fiber-coupled power in 1. T(D, the bonding effect f, r
: By increasing with M-i flow l and 1 addition,
At 4+, simple frost and flow-fiber coupled power linearity is obtained.

The following is an outline of the operating principle of the IJD of the present invention.

An example will be described using an lnG2AsP/lnP-based LED as an example. FIG. 3 shows a cross-sectional structure of an LED according to an embodiment of the present invention. , n-type 1
on the nP substrate 31. The mold 11Pi32, the n-type InGaAsPR33 that will become the active layer, and the p-type InPr@34 are successively formed by liquid phase epitaxy (Shall method, vapor phase epitaxy, Le method, etc.).
, A mask with a target diameter of several 10 μm is formed using photoresist. By science engineering, chi or - Dry Ewo, p
Selective etching l1 on M I n P M'1341 to form a mesa shape.

This mesa-shaped region 35 has an In(3aA, sP active layer 33
The diameter at the point closest to is InGaAs)' activated stone 33
Vμm~10μm distance compared to the west longitude at the farthest point from
Make sure to heat it up. After removing the mask, nm, In]:') f 3 fi ? Form. Next, the n-type 1 and Pl layers 36 are etched 7 to expose gold y on the upper surface of the p-type 1nP mesa region 35. Next 1/Cn
On the surface of type 1nPi plate 36 and p type 1nl'35,
An Au Zn film 37 is formed using a vapor shield, and heat treated in an atmosphere of 1. Type ohmic electrical wall 3
7 in the form f2ν. Subsequently, n-type 1nP group IX, (3
1 was polished to a p4j thickness of approximately 100 μm. After that, this surface was coated with A+IG e Ni vapor>VllF38'G.
Form. By photoresist, p)j, 9. l
In line with the circular Bakun of jNi above the nP meza region 35,
AH (by forming Bac-7 on the jeNi film 38, the target is about 1
2 (Remove A, (jeNi) from the circular ring of Jin+ to form light extraction Yu 39. Finally, R7 or N,
'jJ, heat treated in an ambient atmosphere to form an n-type ohmic electric current 38
'5I: Form. When a forward mechanical current is applied to this LHI), as shown in Fig. 4, in the low current range, the emission diameter increases from 1υ to
The light emitting diameter expands rapidly by about 30 μm, and as the current increases, the light emitting diameter becomes smaller. In the ll-b current range of around -100 mA, the light emitting diameter expands by several/1 m or more. When the diameter of the p-type electric tower 37 is 20 μm, the emission diameter is from about 45 μm to 2511
It changes greatly until it reaches about m. Therefore, this)
For example, when an ED is coupled to a 1':1' core (Mo 50 μm graded index ink), as the current increases, the coupling efficiency increases, so the coupling is cut, Figure 5. As shown above, at 100 mA 1 degree, a market value comparable to that of a conventional LED with a single 20 μm current can be obtained, and moreover, the linearity of the current - line characteristic is significantly improved. The improved G1 leakage Ll characteristics were underestimated in the past.

FIG. 6 shows another implementation of the invention.

This embodiment improves on the embodiment of FIG.
On the substrate 61 is p-type [++PI so62, I) type InGa.
AsP layer 63, r, type IMP Iiii! 64, p type] 0
It is made up of two layers of 6st swords. If the carrier concentration is the same, n
Type InPC)! (conductivity is 11, G is several ten times larger than that of p-type InP). Therefore, in this embodiment, 11. Compared to p-type, I Gl
There is a great advantage in terms of crystal growth that the amount of doping is smaller than i and only the amount of s doping is required.Also, if the amount of doping is the same as that for p-type, the iv of the n-type InP layer 64 can be made thinner. If the column resistance can be reduced (
I),,)! There are also advantages in terms of I'N properties.

In the previous examples, I nGaA4], ' / I
Although we have talked about HP-based LEDs, other Ill-V group compound semiconductor materials can also be used.1. The present invention can also be applied to El).

As mentioned above, the present invention significantly improves the linearity of the output characteristic without impairing the fiber-coupled power. I was able to do it.

[Brief explanation of drawings]

11. Figure 2 is the operating principle 911 of the present invention, and Figure 3.
81.1 implementation of the present invention (X+
of. FIG. 6 is a diagram showing the second embodiment. In the figure, 15, 33, 63 are the lines → 4, 31, 61 is the semiconductor substrate, 11, 13, 34, 35, 62, 65 is the n-type semiconductor layer, 12.36 64 is the n-type semiconductor layer, 14, 37
．． 38 opens the military envoy, and 39 opens the 17 light extraction windows. Representative Patent Attorney Susumu Uchihara (CO) Figure 4 Current (mA) Figure 5 Current (mA)

Claims (1)

[Claims] In a flat light emitting type semiconductor light emitting diode having a double heterostructure and emitting light in one direction perpendicular to the main surface of a semiconductor substrate, a first conductive type ohmic electric tree is disposed between an active layer and a first conductivity type ohmic electric tree. A semiconductor light-emitting diode, characterized in that the cross-sectional area of the first conductive type semiconductor layer in the horizontal direction with respect to the main surface of the semiconductor substrate is made thicker as it approaches the active layer. -Do.