JPS58148481A - Semiconductor laser having embedded heterogeneous structure - Google Patents

Abstract

PURPOSE:To improve resproducibility of crystal growth and to improve a manufacuturing yield rate of BH-LD, by forming a groove which is held between two narrow mesa stripes so as to pierce through a second conductive semiconductor layer, and embedding an active layer in said groove part. CONSTITUTION:The two very narrow mesa stripes 251 and 252 having a thickness of 2mum are provided in advance. An An0.72Ga0.28As0.61P0.39 active layer 205 is grown in the part of the V groove 253 held between the two stripes 251 and 252. Owing to the property of the crystal growth characterized by the fact that the active layer is not laminated on the upper surface of a mesa, the active layer is embedded in a split form in the V groove 253 and is not grown continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a buried heterostructure semiconductor laser in which the shoulder circumference of the active layer is covered with a semiconductor material having a larger energy gap and a smaller refractive index than the active layer.

The integrated heterostructure semiconductor (BH-LD) has excellent characteristics such as low oscillation threshold current, stabilized oscillation transverse mode, and high-temperature operation. It has attracted attention as a light source for AIPA communications. For example, Kaze Omura et al.
electronics Letters) magazine-hlHsl
As reported in Surei No. 14, pages 566 to 568, we have developed an advanced semiconductor laser called the Be laser. K on the Kn-1nP substrate 101 as shown
P-1n1-xGAx%P1-, current plotter layer i
02* p -I mP 1llILpvxyp layer 10
3 is grown in a series of nine semiconductor wafers parallel to the K<011) direction in a striped shape with a radius of 2svxslkk.
is formed by etching to a depth reaching the n-InP substrate 101K, and the n-IrJP buffer layer 104. And a part of the Tnt-zαazAswPt-w active layer 105 is grown so as to be embedded in this layer 110.
It is H-LD. In this case, striped stripes 110 are formed by etching.
A pn-pn junction is automatically formed around the trench 110 containing the zAiwPl-w active layer 105, which automatically becomes a current blocking region.

Shiki Omura et al. obtained a chamber ICW oscillation threshold of 20 snA with a BH-LD having this structure.

However, this type of BH-LD has the following manufacturing drawbacks. In other words, the active layer is separated and buried in the semiconductor, resulting in a BH-LD with good characteristics.
In order to realize this, it must be formed on a semiconductor wafer with a width of only 2 μmIi! In1-zGazA at the edge of the groove
It is necessary to grow the swPl-w active layer 105 in an intermittent manner. Regardless of the situation, in this night, I n
s -z Gax AswP t-gy active layer 105
The drawbacks include poor crystal growth reproducibility, such as continuous growth without being drilled, and poor manufacturing yield.

The purpose of the present invention is to eliminate the above-mentioned drawbacks by providing a semiconductor with an I72 buried hetada structure in which the active layer is reliably embedded in the groove and has good crystal growth reproducibility and manufacturing yield. It is said that the laser is provided.

The structure of the buried heterop-structure semiconductor laser according to the present invention is that the active layer is l18! In a buried heterostructure semiconductor laser in which the active layer is covered with a semiconductor material having a smaller refractive index and a larger energy gap than the active layer, the first
Conductive type semiconductor--A 112 conductive type semiconductor layer is formed in contact with KII, two parallel mesa stripes are formed in the second conductive type semiconductor layer, and a deep layer sandwiched between the two mesa stripes is A cladding layer of III conductivity type and an active layer are laminated at least inside the trench, except for the top surface of the two female stripes, and an active layer is formed by penetrating the II2 conductive semiconductor layer into a nine-structure structure. A cladding layer of the second conductivity type is formed over the entire surface of the mesa stripe, and has a nine-structure structure.

The present invention will be described below with reference to drawings showing embodiments.

Figure 2 shows a sectional view of a BH-LD which is a first embodiment of the present invention. K to obtain H-LD in this way is first
n-4nP substrate 201 with conductivity type (100)
InP buffer layer 202. The p-InP current blocking layer 203, which is a w1212 conductivity type semiconductor, is sequentially laminated and etched twice using a normal photolithography method on a nine-layered semiconductor wafer with a μ width of 2JIm, starting from the flat part. Two parallel mesa stripes 251 and 252 with a height of 0.5 μm are formed between them, and a V 253 with a width of 2 m and a depth of 2 Jlm is formed by pJnP.
11 so as to pass through the current blocking layer 203
Form parallel to the direction. p-rnP current blocking layer 20
3 is made to pass through because otherwise, current will not be efficiently injected into the active layer that undergoes radiative recombination. The thus obtained semiconductor wafer [1114 type cladding layer, n-4nP current blocking layer 2049, In00 layers corresponding to the emission wavelength of 1.3 μm]. Ga6. @A s6. @@ Based on the NH active layer 205, two parallel mesa stripes 251 and 252 are laminated except for only the upper surfaces. This is extremely easy if the mesa stripes are not convergent. Furthermore, a pJnP buried layer 206°, which is a second conductivity type cladding layer, is P-Tnl1410aQ with a composition of 1.1 μm emission wavelength, 11λ
The kss Po, sy electrode layer 207 is continuously laminated over the entire surface.

In this way, in the BH-LD of the embodiment of the present invention, the width is extremely narrow -2 μm to form the buried active layer.
The mesa stripes of the book are prepared in advance, and the In6. g
G4. HAS6. A method of growing the @IP@4 active layer 203 is used. In other words, the present invention utilizes the property of crystal growth in which the active layer is not stacked on the top surface of the mesa, and is formed by cutting off and inserting the active layer inside v#I.

Therefore, unlike conventional examples, the active layer does not grow continuously and the reproducibility of BH-LD crystal growth and manufacturing yield9 deteriorate, and high-performance H-LDs can be produced with extremely high reproducibility. can get. Finally, P type electric fi 208. ya
1i209 of the present invention is formed and the manufacturing is completed.
In the O-order Kl!3 diagram, a BH-LD with an oscillation threshold current of 1 (?"!0rnA at room temperature and a differential quantum efficiency of 5 to 0%) was obtained with an extremely high yield in the dedicated hAsPBH-LD. BH-LD of the second embodiment of the present invention
This can also be done in almost the same way as BH- and LD shown in the first O embodiment. In this case, it is the first conductivity type.

P is applied to the (100) a-TnP substrate 301, which is a conductor substrate.
A Cd diffusion layer 302, which is a second conductivity type semiconductor layer, is formed by dispersing cdt-g, which is a type impurity. The thickness of the layer was 1.5 μm, and as in the tIMl example,
Two parallel mesa stripes 351 and 352 and a stripe 303 sandwiched between them are formed by etching. At this time, by using, for example, a By methanol-based etching solution for etching the grooves 303, it is possible to form an etching field in the shape of an inverted mesa as shown in the figure.

On the thus obtained semiconductor wafer, two mesa stripes 351°35
Except for two parts, the conductive layer is n-TnP.
Current pro, da layer 3o49 emission wavelength 1.3 xm WC equivalent In6y2 o-le & U po, trout active layer 30
5 are sequentially laminated, and a p-InP cladding layer 30 & p-Lk which is a second conductivity type cladding layer is formed over the entire surface.
yt Ga64AI&lIj p and a nodal electrode layer 307 are laminated to obtain the desired BH-LD. Like this K11I2
In the example, Cd is used as the #g2 conductivity type semiconductor layer.
O-diffused Cd diffusion layer 302 on n-TnP substrate 301
However, the epitaxial growth process is a one-time process and has one advantage. In this case as well, of course, the active layer is reliably formed buried inside the etching layer 303, so the manufacturing yield of BH-LD with crystal growth reproducibility has improved by more than 50% compared to the conventional example. Even in the BH-LD manufactured by K in this way, I! Nine structures with the same characteristics as those shown in Example 1 were obtained.

In addition, in the above-mentioned embodiment, an element with a wavelength band of 91 μm was shown using 1ot-xGax material 37P''7 as an active layer and InP as a substrate, but it is not limited to these semiconductor materials.
, GaArAs thread, or other semiconductor materials. Furthermore, in the examples, the part in which the active layer is embedded was formed into a continuous shape and an inverted mesa shape, but the shape is not limited to this, and the groove may have a trapezoidal shape with a flat bottom or a groove of other shapes. I can't help it.

Etching of trout is not limited to wet chemical etching, and techniques such as dry etching may also be used.

A feature of the present invention is that a groove sandwiched between two mesa ribs of different widths formed on the second conductivity type semiconductor layer is formed so as to penetrate through the second conductivity type semiconductor layer. This is because the active layer is partially buried. This is K
Therefore, it is possible to prevent the active layer from growing on the top surface of the narrow mesa stripe, and the active layer is reliably buried in the groove portion, greatly improving the reproducibility of crystal growth and improving BH-L.
D

[Brief explanation of drawings]

Claims (1)

[Claims] In a buried heterostructure semiconductor laser in which the periphery of an active layer is covered with a semiconductor material that has a smaller refraction angle and a larger energy gap than the active layer, a conductive semiconductor and a J12 conductive semiconductor laser are provided. The lid semiconductor layer and the semiconductor layer are
Formed and said #! Two parallel mesa stripes are formed between the two conductive conductive conductor layers, and the part sandwiched between the two mesa stripes has a structure in which the IIM2 conductive conductor semiconductor layer is removed. Except for the upper surface of the mesa stripe, a conductive top layer and an active layer are formed at least inside the layer, and a second conductive top layer is formed on the active layer and the top surface of the stripe. What is claimed is: 1. A semiconductor laser with a diagonal hetagonal structure, characterized in that it has a structure in which: