JPH02105485A - Buried type semiconductor laser - Google Patents

Abstract

PURPOSE:To further improve a response characteristic by forming a plurality of PN junctions having the sufficiently small capacity in an anticurrent region. CONSTITUTION:Two grooves are provided in a multilayer construction having an active layer between a buffer layer 2 and a clad layer 4, while a block layer 5, a undoped layer 6 and a block layer 7 are provided on both side grooves of a striped multilayer construction lying between these grooves, while providing the block layers 5a, 5b and the nondoped layers 6a, 6b between the nondoped layer 6 and the block layer 7 thereto respectively. In this case, the undoped layers 6, 6a and 6b have all got an n-type InP layer having concentration of 1X10<15>cm<-3>. On the other hand, 5, 5a and 5b are all a p-type InP layer having concentration 1X10<17>cm<-3>. Here, each p-n junction consisting of 5 and 6, 5a and 6a and 5b and 6b gets a reverse bias in the state of operation of an element and a depletion layer largely spreads especially on the sides of 6, 6a and 6b so that the junction capacity of p-n junction 10, 11 and 12 is sufficiently small.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an embedded semiconductor laser.

[Conventional technology]

FIG. 3 shows a cross-sectional view of a conventional InP/InGaAsP double channel type brainer buried semiconductor laser (hereinafter abbreviated as semiconductor laser). This semiconductor laser has a striped multilayer structure on a semiconductor substrate 1 in which an active layer 3 is sandwiched between a buffer layer 2 and a cladding layer 4, and on both sides of the striped multilayer structure, a block layer 5, a non-doped layer 6, a block layer 7, It has a structure including a current blocking region made of a semiconductor layer 8 and a cap layer 9 on the top.

In Figure 3, 1, 2.7 are N type 1nP type, 3 is In
GaAsP active layer, 4.5.8.9 is P-type InP M,
6 is a non-doped InP calendar. Here, 5.7.8 is a blocking layer for confining the current, and the non-doped layer 6 is formed for the purpose of improving the response characteristics of the semiconductor laser and reducing the parasitic capacitance of the semiconductor laser.

That is, the non-doped layer 6 usually has a thickness of 1 to 10×101
An N-type 1nP layer with a concentration of 6 cm-3 and an adjacent P-type 1
A PN junction 10 is formed with the nP layer 5, but since the PN junction 10 is in a reverse bias state in the operating state of the semiconductor laser, and the non-doped layer 6 has the lowest concentration among the semiconductor layers in the semiconductor laser, it forms a PN junction. The capacitance due to 10 is the smallest among the capacitance due to other PN junctions in the semiconductor laser.

Here, since the overall capacitance of the semiconductor laser is considered to be the capacitance of the capacitors arranged in series by each PN junction, the smallest capacitance among the capacitors greatly influences the capacitance of the entire semiconductor laser.

On the other hand, the area where the PN junction]0 is not formed is small in terms of area as a whole of the element, and therefore has a small capacitance. Therefore, the capacitance due to the PN junction 10 largely influences the capacitance of the entire semiconductor laser.

[Problem to be solved by the invention]

However, with the demand for faster response, it is not easy to reduce the concentration of the non-doped InP layer 6 in semiconductor lasers with conventional structures.Therefore, it is difficult to reduce the parasitic capacitance of semiconductor lasers, and faster response is required. The drawback was that it could not be handled.

The object of the present invention is to improve the structure of a semiconductor laser, solve the above problems, and obtain a semiconductor laser capable of high-speed response.

[Means to solve the problem]

The semiconductor laser of the present invention has a striped multilayer structure containing an active layer that emits light by current injection, and on both sides of the stripe-shaped multilayer structure, the concentration of P is less than or equal to I x 1017 cm-3.
The semiconductor laser has a structure in which at least a plurality of sets of type semiconductor layers and N-type semiconductor layers are formed such that their PN junctions are reverse biased in the operating state of the semiconductor laser.

[Example 1] FIG. 1 shows a cross-sectional view of a semiconductor laser according to an example of the present invention. The semiconductor laser of this embodiment shown in FIG. 1 has a non-doped InP1 structure compared to the conventional semiconductor laser shown in FIG.
6a, 6b and P-type 1nP layers 5a, 5b are added. That is, buffer layer 2 and cladding N
Two grooves are provided in the multilayer structure with the active layer sandwiched between the two grooves, and a block layer 5, a non-doped layer 6, and a block layer 7 are provided in the grooves on both sides of the striped multi-layer structure sandwiched between the grooves. Block layer 5 between block N7 and block N7
a, 5b, non-doped layer 6a.

6b are provided in pairs. The rest is the same as the conventional example. In this case, undoped InP
Layers 6.6a and 6b both have a concentration of 1 x 1016 cm
-3 N-type InP layer. Also, both thicknesses are 0
．． It is 3 μm. On the other hand, 5.5a.

5b both have a concentration of I x 1017 cm-3 and a thickness of 0.5b.
It is a 1 μm P-type 1nP layer. Here, as shown in FIG. 1, in the operating state of the element, each PN junction consisting of 5 and 6, ra and 6a, and 5b and 6b is reverse biased,
Since the depletion layer spreads greatly especially on the 6.6a and 6b sides, the PN
The junction capacitance of junction 10.11.12 is sufficiently small Furthermore, since the above three PN junctions 10.11.12 are arranged in series, assuming that their respective capacitances are equal, the three P
The capacitance of the entire N junction is 1/3 that of one PN junction. As a result, the parasitic capacitance of the entire semiconductor laser can be reduced to 1/2 to 1/3 compared to the conventional one, and the response characteristics of the semiconductor laser cannot be significantly improved.

[Embodiment 2] Next, FIG. 2 shows a cross-sectional view of a semiconductor laser according to a second embodiment of the present invention. In this embodiment, a multilayer structure including an active layer formed on a semiconductor substrate 1 is mesa-etched to form a striped multilayer structure, and block layers and non-doped layers are alternately laminated on both sides of this striped multilayer structure. It has a structure in which striped N structures are embedded. Block layer 7. Semiconductor M8. The cap layer 9 is the same as the conventional one. In FIG. 2, 6c, 6d.

6e, 6f, and 6g all have a thickness of Ojμm and a concentration of 1X
It is an N-type InP layer of 1016 cm-3 and 5c.

5d, 5e, 5f, and 5g are all P-type InP Jil with a thickness of 0.1 μm and a concentration of I×10 16 cm −3 . Although the semiconductor laser of the second embodiment has a buried cross-sectional shape different from the semiconductor laser of the first embodiment, it has a PN junction 10 with a sufficiently small capacitance in a region other than the region serving as a current path.
, 11, 12, 13, 14, and has the same effect as the semiconductor laser of the first embodiment.

Furthermore, the semiconductor laser of this example has P-type 1nP layers 5c, 5d, 5e, 5f, and 5g forming the above-mentioned PN junction.
and N-type InP layers 6c, 6d, 6e, 6f, and 6g are all 1
Since the semiconductor layer has a low concentration of x10110l6', the capacitance of each PN junction is further reduced, and the semiconductor laser has a further improvement effect compared to the semiconductor laser of Example 1, which has a large number of PN junctions.

〔Effect of the invention〕

As explained above, in the semiconductor laser of the present invention, by forming a plurality of PN junctions with sufficiently small capacitance in the current blocking region, the capacitance of the above-mentioned added PN junctions as a whole is proportional to the reciprocal of the formed PN junctions. Furthermore, since the capacitance of the above-mentioned PN junction is smaller than the capacitance of other PN junctions in the semiconductor laser, there is an effect that the capacitance of the entire semiconductor laser can be reduced.

As a result, the response characteristics could be further improved.

[Brief explanation of drawings]

1 and 2 are cross-sectional views of a semiconductor laser according to the present invention, and FIG. 3 is a cross-sectional view of a semiconductor laser having a conventional structure. 2... Semiconductor substrate, 2... Buffer layer, 3... Active layer, 4... Cladding layer, 5.5a, 5b, 5c. 5d, 5e, 5f, 5g... Block layers of conductivity type opposite to the substrate, 6.6a, 6b, 6c, 6d. 6e, 6f, 6g... Non-doped layer, 7... Block layer of the same conductivity type as the substrate, 8... Semiconductor layer of the opposite conductivity type to the substrate, 9... Cap layer, 10, 1, 112 ．．
13.14...PN junction.

Claims (1)

[Claims] In a buried semiconductor laser having a current blocking region formed by stacking a plurality of semiconductor layers on both sides of a striped multilayer structure containing an active layer that emits light by current injection, the current blocking region is provided with a plurality of PN contacts. The PN junction is formed so as to be reverse biased in the operating state of the semiconductor laser, and the concentration of at least one of the P-type semiconductor layer and the N-type semiconductor layer constituting the PN junction is 1×10^1^
An embedded semiconductor laser characterized by having a diameter of 7 cm^-^3 or less.