JPS5875877A - Monitor built-in semiconductor laser element - Google Patents

Abstract

PURPOSE:To build-in a high sensitivity monitor without deterioration of laser operating characteristics in a monitor built-in semiconductor laser element by integrating a phototransitor structure containing a base region formed of a collector electrode and a photo-occluding layer isolated from a current injection electrode. CONSTITUTION:This laser is composed of an active region 11 having a buried structure formed on an n type semiconductor substrate 10, a clad region 12 made of a p type semiconductor, a photoabsorbing layer 13 on the region 12, an n type side electrode 19, a current injection electrode 17, and a collector electrode 18. The layer 13 is formed of n type reverse to the region 12 at the time of growing crystal, and a current injection stripe region 15 connected to the regions 14, 12 by thermal diffusion of the p type impurity is contained therein. The electrodes 17, 18 are electrically isolated via an insulating film 16.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in semiconductor laser devices used as light sources for optical fiber communications or optical information processing.

Semiconductor laser elements have been increasingly used as light sources for optical fiber communications and optical information processing in recent years due to their small size, high power efficiency, long lifespan, and ease of maintenance not found in other lasers. However, semiconductor lasers have the characteristic that their oscillation threshold changes with changes in ambient temperature, and accordingly, their optical output fluctuates. For this reason, conventional semiconductor laser devices are used together with a photodiode to monitor variations in optical output, and a bias current adjustment circuit is added to maintain the optical output at a constant value ζ. A semiconductor laser device with a built-in monitor is also known, which monolithically integrates a photodiode and a semiconductor laser device for the purpose of reducing the number of steps for assembling the device and downsizing the device as a whole.

However, in a conventional semiconductor laser device with a built-in monitor, a monitor photodiode is formed to be cascaded with the laser in the optical output beam direction of the laser. For this reason, in the conventional example, a laser was constructed using an etched mirror surface whose characteristics were inferior to that of a cleavage plane of a crystal, and a photodiode separate from the laser was manufactured. A mirror surface with poor characteristics causes deterioration of laser operation, and the photodiode's light absorption section, which is shared with the active layer of the laser operating section, has the disadvantage of becoming an obstacle to improving the photodiode's characteristics. Ta.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a semiconductor laser device with a built-in monitor that has a built-in highly sensitive monitor and does not cause deterioration of laser operating characteristics.

According to the present invention, in a current injection type conductor laser element having a semiconductor multilayer structure including a semiconductor heterostructure, a collector electrode and a light absorption layer are formed, which are separated from a current injection electrode. A semiconductor laser device with a built-in monitor is obtained, which is characterized in that a phototransistor structure including a base region is integrated.

Next, the present invention will be described in detail with reference to the drawings.

The drawing is a cross-sectional view perpendicular to the laser light output beam direction of one embodiment of the present invention. In this embodiment, an active region 11 having a buried structure formed on an n-type semiconductor substrate IO and a cladding region 1 made of a p-type semiconductor
2, a light absorption layer 13 on the cladding region 12, an n-side electrode 19, a current injection electrode 17, and a collector electrode 18. The light absorbing layer 13 is the cladding region 11 during crystal growth! The current injection stripe region 1s is formed of n-type, which is the opposite conductivity type, and then connected to the collector region 14 and cladding region 12 by thermal diffusion of p-type impurities. Note that the current injection electrode 17 and the collector electrode 18 are electrically separated by an insulating film 16. To describe the composition and dimensions of each main part, the semiconductor substrate 10 is made of an ImP single crystal with a plane orientation (10G) and has a thickness of about 7 mm.
The active region 11 has a width of 2 pm, a thickness of go, 1 $fim, and an oscillation wavelength of 1.3.
In&ra Gate-Person 1&IlP equivalent to am
The &44s cladding region 12 is made of Zm-doped Ink with a thickness of about 2 μm on the active region 11, and the light absorption layer 13 is made of Zm-doped Ink with a thickness of about 1.5 μm.
5μm1 absorption edge wavelength 1115mIc@? Inty to A
mGaassA@a/Snow Pa5s, the current injection stripe region 1s is inverted to p-type by Zn diffusion with a depth of about 2 μm, and the width of the collector region 14 with a width of about 8 μm centered on the active region 11 is Zn diffused with a depth of 1 μm. ζ Therefore, the current injection stripe region 1b, which is inverted to p-type, is about 10 μm.
The insulating film 16 has a stripe shape with a width of about 201 sm provided at intervals of 1810 m with a thickness of $0.24 m,
The s-flow injection electrode 17 and the collector electrode 18 have a thickness of approximately 0.3
μm μm u-Zn alloy, n-side electrode, 19 has a thickness of about 0.3
It is a μm U-8N alloy. The device is cut out by cleavage and a direction perpendicular to the stripe direction of the active region 11, and its resonator length is about 250 μm.

Now, when a positive voltage is applied to the current injection electrode 17 and a negative voltage is applied to the n-side electrode 19, and a current is injected into the active region 11 through the current injection stripe region 1s and the cladding region 12. Start laser oscillation. A negative voltage is applied to the collector electrode 18 in advance. A portion of the laser light output scattered by the optical imperfection a at the interface between the active region 11 and the cladding region 12 is absorbed by the base region 11m and generates a photoexcitation current.

This photoexcited current flows through the cladding region 12 and the base region 13.
A high current amplification wheel number ζ of the transistor structure is increased by the heterojunction pup-type photoconductor formed by the collector region 14 and the collector region 14, and is taken out from the collector electrode 18. In conventional integrated photodiodes, the light absorption layer of the photodiode was often the same as the active layer of the laser, resulting in low light reception efficiency and only a small monitor current. In the embodiment, the set of light absorption layers 13-
Since the composition of the active region 11 can be optimized independently of the composition of the active region 11, high light reception efficiency can be obtained, and since it is amplified by the high amplification factor of the phototransistor structure, a sufficient monitor current can be obtained by using only a small amount of scattered light. be able to. Further, in this embodiment, since the monitor section is arranged in parallel with the laser section, there is an advantage that a resonator can be formed by cleaving the crystal, as in the conventional semiconductor laser device.

By the way, in the above embodiment, the cladding region 12 does not have a current blocking structure, but a current blocking layer made of an n-type semiconductor may be added. Furthermore, the structure of the current injection type semiconductor laser beam is not limited to the above-mentioned structure, and may be any other type of embedded structure, or may be a non-embedded structure in which the active layer has a flat width. Semiconductor materials are not necessarily I
nk/lmGamussr jl111C as well as GaAs
Any material that can be used to construct a semiconductor laser device, such as Ga AI A S type, is suitable.

Finally, to summarize the advantages of the present invention, by incorporating a highly sensitive monitor into a high-performance semiconductor laser device that uses cleavage planes, a semiconductor laser device with a built-in monitor that is convenient for stabilizing high output can be obtained. That's true.

[Brief explanation of the drawing]

Drawing is 15I! It is a sectional view of an example. In the figure, 10... semiconductor substrate, 11-... active region, 12... cladding region, 13......
Light absorption layer, 1381...Base region, 14-...
- Collector region, 15... Current injection stripe region, 16... Insulating film, 17... Current injection electrode, 18... Collector electrode, '19・
...This is an n-side electrode.

Claims (1)

[Scope of Claims] (1) A current injection type conductor laser element configured with a semiconductor multilayer structure including semiconductor heterojunction,
A semiconductor laser device with a built-in monitor, characterized in that a phototransistor structure including a collector electrode separated from a current injection electrode and a base region formed of a light absorption layer is integrated. (8) The current injection type medium conductor laser element has a buried structure active region, and the base region is provided at a position ζ apart from above the active region. The semiconductor laser device with a built-in monitor according to item 1.