JPS5948968A - Light-emitting diode - Google Patents

Abstract

PURPOSE:To obtain the light-emitting diode (LED) having rectangular light intensity distribution by a method wherein an active layer and a P-type clad layer are superposed on the N type clad layer clocated on an N type semiconductor layer through the intermediary of a P type intermediate layer, a P type current blocking layer is provided on the side face of a circular cylinder, and an N type current squeezing layer is provided on the region other than the upper surface of said circular cylinder. CONSTITUTION:An N-InP layer 21, an InGaAsP active layer 22, a P-InP intermediate layer 23, an active layer 24 and a P-InP layer 25 are superposed on an N-InP substrate 1, and a cylindrical body of 5-20mum is formed by performing a mesa etching. The horizontal leak of current injected into the active layer can be prevented by surrounding the horizontal circumference of the active layers 22 and 24 with a P-InP 26 having large Eg, an N-InP current squeezing layer 27 is provided on the region other than the top surface of the circular cylinder, and a P-InP layer 28 and a P-InGaAsP cap layer 5 are superposed. According to this constitution, as the carrier leaked on the first active layer is caught by the second active layer, a saturation tendency is low in current and optical output, and besides, light intensity distribution is rectangularly formed even when the diameter of emitted light is reduced, the coupling efficiency of optical fibers is excellent and an LED of high output power can be obtained.

Description

[Detailed description of the invention] The present invention relates to a light emitting diode for original communications.

An example of a conventional light emitting diode for optical communication is an InGaAsP/InP light emitting diode with a wavelength of 1.3 μm as shown in FIG. In the figure, 1 is an n-InP substrate, 2 is an n-InP substrate, and 2 is an n-InP substrate.
・, n-type cladding layer made of InP, 31d nGaA
Active layer consisting of sP (22-1.3 μm), 4 is p・I
p-type cladding layer made of nP, 5 is 1) InG-aA
A cap layer consisting of sP, 6 is 5io211iH,
7 is a p-electrode, and 8 is an n-electrode. In this older IL diode, the entire electrode is formed only in the circular electrode region 11 by interposing the 5iOz film 6 between the n-electrode 7 and the cap layer 5. Therefore, the active layer 3 under this circular electrode region 11 becomes a light emitting region. However, normally, the lateral spread of low flow in the p-type cladding layer 4 is 9 (arrow N), and the lateral spread of carriers in the active layer 3 (arrow 13).
), the light intensity distribution in the original light area is not rectangular, but
It becomes trapezoidal. As the diameter of the circular electrode 11 becomes smaller, such a phenomenon becomes more noticeable, and the light intensity variation a becomes closer to a Gaussian distribution.

-11 In particular, it is known that the occupancy efficiency between the original fiber and the light emitting diode improves by decreasing the light emitting diameter, but if the light diameter is made smaller, M'll:17
At tJ2 of 1i, the light intensity distribution does not have a rectangular shape.
The hexagonal alloy had the disadvantage that it had a Gaussian distribution, making it difficult to obtain good coupling efficiency. For example, when the light intensity A has a Gaussian distribution, the coupling efficiency deteriorates by about 2 dB compared to when it has a rectangular distribution.In this way, in conventional original pro diodes, the coupling efficiency decreases even if the emission diameter is made small. Since the splitting is not good, there is a drawback that the incident wave of the original fiber becomes smaller.

On the other hand 1. When the i/i: emission diameter is made smaller to improve the coupling efficiency, the frost and light density becomes very thick when the operating temperature and flow are constant, and therefore the injected carrier density in the active group layer increases. , a heterobarrier between the active layer and the cladding layer? Overcome, t- and carrier ()1! ! There is also a thing called ``re-debutsu''.

This is a phenomenon called carrier leakage (or carrier overflow). Conventional original like this)
°1-da・In the ode, % 4'l'i −/Y
: When the diameter is small, when the operating current is gradually increased, the carrier leakage becomes noticeable, so the optical output does not increase much and becomes saturated, which is a drawback.

The purpose of the present invention is to have a rectangular light intensity distribution even when the emission diameter is made small, to have good coupling efficiency with the fiber, to have little influence of carrier leakage gauge, and to have little tendency to saturation in the current-light output characteristics. An object of the present invention is to provide a light emitting diode with a large light output.

41 of the present 3G light emitting diode, a first conductivity type cladding layer formed on a first conductivity type semiconductor substrate, and at least two or more layers formed on this first conductivity type cladding layer. consisting of a disc-shaped active layer, a disc-shaped intermediate layer sandwiched between the upper and lower sides by the active layer, and having a forbidden firefly width larger than that of the active layer; the active layer and the intermediate layer; Lamination) lI! A disk-shaped second plate formed on the f-structure
a conductive type cladding layer; a second conductive type current blocking layer formed on the first conductive type cladding layer or the semiconductor substrate and extending over the side surface of the laminated structure; 1d 71'i & is entirely provided with a current confinement layer of the first conductivity type which does not fall off.
I'm with Maki.

I would like to congratulate you on the complete review of this book with the following drawings.

Figure 2 shows that the present invention has a wave of 13 μm (n(
1a-A cross-sectional view of an AsP/InP light emitting diode, i, lx t + each; m indicates a groove component; In the figure, 21 is a type 11 clad Ia consisting of n・, [nP, 22 &i J n(Ja-AsP(3g~
1\4.
23Id, p v (1, intermediate j so, 2
4 is IJ ・111Ga-AsP (λg ~ 1.3 μm
) consists of the second life 1゛Junoso, 25 is ■゛・InP
p:;W cladding layer, 26 is 1) InP
Current block consisting of 27 & J11 l, n
, a current confinement layer consisting of L', 28 a buried layer consisting of I n P, and 29 4) + 11) for current confinement.
n, j・1″・￥謂, 30 is non-reflective coating, 3
1r'' is a light emitting region, and 32 is a flat portion.

In this embodiment, the active layer 22 and the second active layer 24 of .
Because it is surrounded by a current block made of InP, it is almost impossible for the ・T Yaria injected into the active layer to leak into the active layer and spread. The light emitting region 31 is laterally surrounded by an n-type cladding layer 21, a current blocking layer 26 made of p-InP, a current confinement layer 27 made of p-InP, and a buried layer 28 made of p-InP. pnpnt? Because of the J structure 29, the current flowing around the entire light emitting area 31 is blocked. In this way, the carrier leakage that spreads laterally from the active layer and the current leakage that flows around the light emitting region 31 are almost 4( ) (), so the light intensity distribution of the light emitting region 31 becomes rectangular. It also has good efficiency and can increase the optical power input into the fiber.

The light emitting diode of this example has two active layers, and electrons and holes are first injected into the first layer 711 and the hole 22, where they recombine and emit light. At this point, when the current is gradually added to the full range, the active 1, 22, and 6' carrier intensities become [1i thick] and carrier leakage occurs. In general, a hole has a ``b,'' because the material I is thicker than the child.
Career leakage is tl'c child completion: , 1. 'P
The total amount is so small that it can be ignored. Therefore, career
Caging occurs significantly only for injected electrons, and electrons overflow from the first active layer 22 to the p-type intermediate t<:h 2 :3. This '4 [most of the overflowing 1] passes through the 1)5 intermediate layer 23 and is injected into the active/column layer 24 of @2. Since the active layer 24 of the tail 2 is not very large, the injected electrons are recombined into π5 elements without carrier leakage.

As described above, in the light-emitting diode of the non-example, even if carrier leakage occurs, the influence of carrier leakage is lj, and the effect of carrier leakage is lj, which is 1. ljE (Thus, the current-light output is saturated with poetry/l'll li,'(4 times or less ij"<golden dust.

, ] (ni/f: FU Example's house) Y, diode's ·n ° old' ``Method of ++y+'.

make light.

First, an n-type cladding layer 21 (nI
nP ) k 1~2 0 It n1lj-
4 pieces (rJ, 51Zln 4ml,
1. l31 )t+';i%ffj 2 2 (,
1nQa8s λg, 1.3 μl]l) k
'0.1~4μm preferably 1μm 4j@l
Ki, p-type intermediate 1 the i23 (p-InP) ko, 05~
3 μIY1tl-j-4: L, < is about 0.2 μnl, second active layer 24 (p-1nQsASPλR・~
1. ．． 3 tJ+i) is preferably 0.1 to 4 μm lj:
Approximately 1 μm, p.In
, P) 'e 0.1-5μm Preferably 0.5μm
The crystal grows to about m. In this case, the crystal growth method may be any method such as liquid phase growth, vapor phase growth, and molecular adaptation method. Next, the light emitting area 31 is etched by photo etching.
Mesa etching is performed, leaving only the chisel. The diameter of this mesa etching is suitably 40 μIn or less, preferably 5 to 20 μm. This mesa etching depth is the n-type cladding layer 21
Continue until you reach . During this etching, etching may be carried out to completely remove the n-type cladding layer 21 on the planar surface S32, or the etching may be carried out to the extent that the n-type cladding layer 21 is completely removed as shown in [nui].
There is no problem even if the etching is stopped in the middle or at the upper interface of 1.

Next, a second crystal growth is performed. This crystal/JIC-J
It is preferable to use the method for liquid phase formation-1. Suzu p・
Current blocking layer 26' made of InP! i? (1
, 1 to 3 μm, preferably about 1 μm, then nInP or 1
The current confinement layer 27 has a thickness of 0, i to 3 μm, preferably t
yoJl, about tm, then embedding consisting of pfnP/
G12 with 8 (] 55-10 μm or 2-: (A
Finally, a key layer 15 (22 to 12 μm) made of pIn(,+a-AsP) is formed to a thickness of 0.2 to 3 μm.
Preferably (about 1 μm crystalline)
Ru. After these two times 11 crystal growth, the diameter of the original round region is 4
As small as 0 μm 1 person, I, ・9 go, and IJ, 1,
・,] By setting a small degree of supercooling of the bath liquid, ・, 1-, flow block layer 2 (i and 'b, flow acupuncture layer 27 is 1..: in ICi area 31. Missing 11'
, 1st b1 was recovered, and uniform 'I'+l was accepted in the 21st n)
ノ、'jji h"l'j'l" (g VCS
i O2l17.5 J・L' V J) 7 left J57
．． , ) or by using a sputtering method, photoetching, or rinsing, and the p-electrode 30 is formed by using a sputtering method or the like. 1' 1 anti-reflective coating 30 for 1 poem [Sonari Sara VC
n notification 4iflv8 complete formation.

/1(Rishiku (1 case is signed fc for the 2nd layer active layer and 1st layer, or 1 does not fit this and more than 31 so)) So (1゛・￥
”? Even if it's 7, it's IJ.

In addition, between the active fourth layer and the cladding layer, there is a semi-integrated layer or split elm C which becomes a buff of 117 width (river prohibition).
It's okay to stay. The father is n-type in this example, ? +l; 14 editions in total
4, but a p-type substrate may also be used. In addition, although the p-type electrode 'zsi02 constricted structure is used in the present 77Ri example, it is not necessarily limited to this, and for example, p-type impurities may be applied to the n-type cap layer only in the vicinity of the entire light emitting region to generate current. Various structures such as a so-called planar structure forming a passage or a full-surface electrode structure can be adopted. In this example, the composition of the active layer is 1.3μrn In()aAsP.
InGa with a wavelength of 1.0 to 1.7μIn￥1: which is almost lattice matched to InP was used.
Even if used for AsP or InGaAs k active layer,
It is clear that non-invention is applicable.

In addition, in non-examples, InGa /is J
'/I n P system is used, but not limited to this, other moon phases Ga
The non-invention can also be increased in A6As/GaAs%.

[Brief explanation of the drawing]

Figure 1 shows the conventional 1 nGa A 5 at a wavelength of 1.3 μm.
A cross-sectional view of a P/I nP light emitting diode, FIG.
G a A s P/', 1 n P<it! ;)
Y; is a cross-sectional view of a diode. In the figure, 1...
... n・I n P , I,! : Board, 2, 21...
・N-type cladding layer, 3...active layer, 4.25...
.....1) type, clandestine η, 5......to cap Jt 6...5iU21 odor, 7...p electrode, 8...n fll pole, 11.・・・Circular l
-11i',,) Meat pursuit, 12...4 white light window, 22...7 fortune-telling of month number 1, 1st life, 1st adventure, 23...
...p-type intermediate layer, 24...second life 1 life 1 so,
26...Current block layer, 27...Frost; Nagasaka layer, 28...Buried layer, 29...I
) nl) IN1''#ノe-130... control (1-
Reflective coating, 31...°C range of origin, 3
It is 9 NIS per day. 71 catties) /l pc, 2y-+ 304

Claims (1)

[Claims] i group 1 guide city j! ;lj formed on the semiconductor substrate;
a conductive type cladding layer; and at least two or more disk-shaped active layers formed on the first conductive type cladding layer;
A second conductive type intermediate layer sandwiched between the upper and lower active layers and having a disk shape and a forbidden band width larger than the active layer Q, the active layer and the t'+tJ intermediate layer small intermediate layer laminated structure. a disk-shaped second conductivity type cladding layer formed on the cladding layer 11;
A first power-gaining type cladding layer or a second power-gaining type cladding layer formed on the semiconductor substrate and covering the entire side UkI of the laminated structure;
a current blocking layer and a current blocking layer formed on the current blocking layer;
A light emitting diode characterized by having a current confinement layer of a first conductivity type that does not cover a multilayer structure.