JPH01268085A - Semiconductor laser - Google Patents

Abstract

PURPOSE:To obtain a semiconductor laser wherein a lateral single wave guiding mode is obtained with good reproducibility, leakage currents in a current blocking layer are less, parasitic capacitance is less and therefore high speed operation is possible at a low threshold value, by providing insulating organic film layers on the right and left sides of an active layer, and providing interface between the insulating organic film layer and a conductive semiconductor layer to the same plane as the lower interface of the active region. CONSTITUTION:Conductive type semiconductor layers 13 and 11 having a refractive index lower than the refractive index of an active region and a forbidden band width larger than the forbidden band width of the active region are arranged at the upper and lower parts of the active region 12 in a semiconductor laser. Semiinsulating organic film layers 17 are provided at the right and left parts of the active region 12. The interface between said insulating organic film layer 17 and said conductive type semiconductor layer 11 is provided at the same plane of the lower interface of the active layer 12. For example, an undoped InGaAsP layer is used for said active layer 12. A zinc doped InP layer is used for the clad layer 13. A zinc doped InGaAsP layer is used for a contact layer 14. Polyimide is used for the insulating organic layer 17. A sulfur doped InP substrate is used for a semiconductor substrate 10.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a semiconductor laser.

(Prior Art) A semiconductor laser using an insulating organic film layer as a current blocking layer is expected to have a low threshold and high speed operation because there is no leakage current in the current blocking layer and the parasitic capacitance is small. In addition, such a semiconductor laser has a simple blocking structure, so it is possible to reduce the cost. A conventional example of a semiconductor laser having such a structure (862
Spring Proceedings of the Japan Society of Applied Physics, Lecture No. 28p-ZH-1
) is shown in Figure 3. In FIG. 3, the active layer 12 is sandwiched between an n-type buffer layer 11 and a p-type cladding layer 13 from above and below, and current is passed through insulating organic film layers 17 located on both sides of the ridge structure including the active layer 12. narrowed. Therefore, electrons are transferred to the n-type electrode 15, the n-type semiconductor substrate 10, and the buffer layer 1.
1 into the active layer 12, while holes are injected into the p-type electrode 1
6. Active layer 1 via contact layer 14 and cladding layer 13
Injected into 2.

(Problems to be Solved by the Invention) However, the conventional semiconductor laser using an insulating organic film layer has a drawback in that it is difficult to increase the yield. This is because it is difficult to accurately control and stop etching in the middle of the p-type rad layer 13, and the shape of the ridge structure including the active layer 12 varies, making it difficult to obtain the transverse wheel-waveguide mode with good reproducibility. be.

The purpose of the present invention is to obtain the transverse wheel-waveguide mode with good reproducibility, to have low leakage current in the current blocking layer, and to have small parasitic capacitance, so low threshold and high-speed operation are possible, and a high manufacturing yield can be expected. The purpose of the present invention is to provide semiconductor lasers.

(Means for Solving the Problems) The semiconductor laser of the present invention has a refractive index lower than the refractive index of the active region above and below the active region, and a forbidden band width larger than the forbidden band width of the active region. In a semiconductor laser including a conductive semiconductor layer, an insulating organic film layer is provided on the left and right sides of the active region, and an interface between the insulating organic film layer and the conductive semiconductor layer is a lower interface of the active region. It is characterized by being on the same plane as the

(Function) In the semiconductor laser according to the present invention, when forming a mesa including an active region by etching, the mesa shape can be formed with good reproducibility by using selective etching that takes advantage of the difference in composition between the active layer and the cladding layer. In addition, since the interface between the insulating organic film layer and the cladding layer is on the same plane as the lower interface of the active region, the difference in refractive index between the insulating organic film layer and the active region is reduced and the horizontal - The width of the active region required for the waveguide mode is lpm or more. Therefore, the transverse wheel-waveguide mode can be obtained with good reproducibility. Furthermore, since the insulating property of the insulating organic film layer is sufficiently high, the injection current flows only to the active layer, the leakage current is significantly reduced compared to the conventional one, and a low threshold value can be obtained with good reproducibility. Furthermore, since the dielectric constant of the insulating organic film layer is smaller than that of a semiconductor, parasitic capacitance is reduced and high-speed operation is possible. In addition, compared to insulating inorganic films, the stress generated at the interface with the semiconductor and in the film is much smaller, so the effect of stress on laser characteristics can be reduced.
It has the advantage that cracks do not occur even when the film thickness is 2 pm or more.

(Example) Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a sectional view of a semiconductor laser showing an embodiment of the present invention. In this embodiment, the active layer 12 has a forbidden band width of 0.95e.
The buffer layer 11 is an InP layer doped with sulfur to I x 1018 cm', the cladding layer 13 is an InP layer doped with zinc to I x 11018 a', and the contact layer 14 is an InP layer doped with zinc to I x 10 cm'.
Polyimide was used for the 19 cm' doped InGaAsP layer and the insulating organic film layer 17. In addition, the semiconductor substrate 10
A sulfur-doped InP substrate was used. Insulating organic film layer 1
Since the interface between 8 and the buffer layer 11 is on the same plane as the lower interface of the active region, the difference in refractive index between the insulating organic film layer and the active region is reduced, and the transverse shear-waveguide mode is created. The width of the active region required for this purpose is now comparable to that of a typical buried semiconductor laser. FIG. 2 is an explanatory diagram of the relationship between the guided mode gain and the active region width of the semiconductor laser according to the present invention, calculated using the finite element method. From this, in the transverse wheel-waveguide mode condition, when the active layer thickness is 0.1 pm, the active region width is lpm-2 pm. Since it is easy to set the active layer width within this range, it is possible to easily set the width of the active layer within this range.
A guided mode was obtained. In addition, the active layer 12 is sandwiched between the buffer layer 11 and the cladding layer 13 from above and below, and between the insulating organic film layers 17 from the left and right, and the i-stream is sandwiched between the insulating organic film layers 17 located on both sides of the active layer 12. narrowed by Therefore, electrons pass through the n-type electrode 15 and the buffer layer 11 to the active layer 1.
On the other hand, holes are injected into the active layer 12 via the p-type electrode 16, the contact layer 14, and the cladding layer 13.

As a result, the injection current flows only through the active layer, the leakage current is significantly reduced compared to the conventional method, and a low threshold value of about <10 mA with good reproducibility is obtained. In addition, the parasitic capacitance is the insulating organic film layer 17.
A modulation band of 10 GHz or more was obtained.

In this example, the buffer layer 11 is an InP layer doped with sulfur to Ix11018a', and the active layer 12 is an undoped InGaAs layer with a forbidden band width of 0.95 eV.
The P layer, the cladding layer 13 is an InP layer doped with zinc at a concentration of 1 x 1018 cm-3, and the contact layer 14 is doped with zinc at IX
Using an InGaAsP layer doped with 11019a', a double heterostructure consisting of these layers was laminated on a (100) plane sulfur-doped InP substrate by hydride vapor phase epitaxy. In this hydride vapor phase growth, the growth temperature is 690°C.
In metal and Ga are used as group III materials and V raw materials.
Metal, arsine, and phosphine gas were used, respectively. Next, a mesa having a mesa width of 51.1 m, a height of 2.5 μm, and an active region width of 1.5 pm was formed on the wafer having the double heterostructure using conventional photolithography and selective chemical etching. Polyimide layers were formed as organic film layers 17 on both sides of the mesa. After this, electrodes were formed.

The reason why polyimide was used as the insulating organic film layer in the above embodiment is that it can withstand the thermal process of electrode formation. However, the process for forming the electrodes does not necessarily depend on the order and method used here, so other materials may be used as long as the dielectric constant is lower than that of the semiconductor. Although the semiconductor layer is grown using the hydride vapor phase epitaxy method, it can also be realized using an epitaxial growth method such as a liquid phase epitaxy method, an organometallic vapor phase epitaxy method, a chloride vapor phase epitaxy method, or the like.

Although InGaAsP/InP semiconductor materials were used in the above embodiments, GaAlAs/GaAs, TnGaAIA
Application is also possible to semiconductor lasers made of other III-V group raw conductor materials such as s/InP.

(Effects of the Invention) The semiconductor laser according to the present invention can obtain a transverse shear-waveguide mode with good reproducibility, has low leakage current in the current blocking layer, and has small parasitic capacitance, so it is capable of low threshold and high-speed operation.
High production yields can be expected.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a semiconductor laser which is an embodiment of the present invention, FIG. 2 is an explanatory diagram of the relationship between waveguide mode gain and active region width of the semiconductor laser according to the present invention, and FIG. 3 is a diagram illustrating a conventional example. 1 is a cross-sectional view of a semiconductor laser. 10... N-type semiconductor substrate 11... Buffer layer 12... Active layer 13... Cladding layer 14... Contact layer 15... N-type electrode 16... P-type electrode 17... Each insulating organic film layer is shown.

Claims (1)

[Claims] In a semiconductor laser in which conductive semiconductor layers having a refractive index lower than the refractive index of the active region and a forbidden band width larger than the forbidden band width of the active region are disposed above and below an active region, on the left and right sides of the active region. A semiconductor laser comprising an insulating organic film layer, and an interface between the insulating organic film layer and the conductive type semiconductor layer is on the same plane as a lower interface of an active region.