JP2000031604A - Photosemiconductor crystal and semiconductor element using the same, and manufacture of photosemiconductor crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a means for eliminating the dependence on the temperature of the wavelength for light emission of a photosemiconductor element being manufactured, using a photosemiconductor crystal. SOLUTION: This photosemiconductor crystal is constituted by stacking successively an InGaAsP light confinement layer 20 which has a composition of 1.3 μm in wavelength for light emission, an InGaAsP active layer 30 which has the composition of 1.5 μm for light emission wavelength, with its composition separated by the immiscibility that the crystal has, an InGaAsP light confinement layer 40 which has the composition 1.3 μm for wavelength of light emission, a p-type InP clad layer 50, and a p-type InGaAs electrode layer 60 in this order.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical semiconductor device used for optical communication and the like, a semiconductor crystal as a base thereof, and a method of manufacturing an optical semiconductor crystal. The present invention relates to an optical semiconductor crystal capable of providing an optical semiconductor element and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, an optical communication system has become important as an infrastructure. The development of this optical communication technology has been accompanied by a reduction in loss of an optical fiber and InGaAsP which becomes a material of a semiconductor laser and a photodetector. It largely depends on the research and development of mixed crystal semiconductors. InGaAsP is
Today, many optical semiconductor devices made of InGaAsP mixed crystal semiconductors are used in optical communication systems because their emission wavelengths completely cover the wavelength range used in optical communication systems and high-quality crystals can be easily manufactured by epitaxial growth. It is used for

Further, in order to cope with the trend of an era in which multimedia technology has been remarkably developed in recent years, it is expected that large-capacity information such as image information will be frequently communicated in the optical communication system in the future. Therefore, it is necessary to increase the speed of information transmission and increase the capacity of transmission information. A wavelength division multiplexing (WDM) communication system is considered to be the most promising method for dramatically increasing communication capacity and enabling flexible communication network management. Requirements for semiconductor lasers used in this WDM communication system Is that the fluctuation of the oscillation wavelength due to temperature is small.
Since the band gap of an nGaAsP mixed crystal semiconductor decreases as the temperature rises (the temperature dependence is negative), the temperature dependence of the oscillation wavelength of a semiconductor laser using this as an active layer is inevitable.

_{Meanwhile, In 1-x Ga x As} y P -y (0
≤ x ≤ 1, 0 ≤ y ≤ 1) Mixed crystal semiconductors are important as materials for semiconductor lasers for optical communication, and many practical semiconductors having an oscillation wavelength of 1.3 μm and 1.55 μm using InGaAsP mixed crystal semiconductors. Lasers have been manufactured. This I
An advantage of the nGaAsP mixed crystal semiconductor is that the band gap can be changed over a wide range by changing the composition (x, y). It is to be. Since the InGaAsP mixed crystal semiconductor having the composition of the immiscible region is thermodynamically unstable, it is not a uniform composition, but a portion where GaP is larger than the average composition and InAs is higher than the average composition.
Tends to separate the composition from the portion where the amount is large.

[0005] The existence of this composition separation is based on the liquid phase growth method (LP
E), an InGaAsP mixed crystal semiconductor grown by metal organic chemical vapor deposition (MOVPE) or gas source molecular beam epitaxy (GSMBE).

[0006] Conventionally, InG has no composition separation.
An optical semiconductor device has been manufactured using an aAsP mixed crystal semiconductor. Further, although composition separation of an InGaAsP mixed crystal semiconductor has already been known, it has been conventionally avoided to use this as deteriorating crystal quality.
As a method of eliminating the composition separation, a method of increasing the growth temperature to a temperature at which the immiscible region disappears has been adopted.

On the other hand, attempts have been made to eliminate the temperature dependency of the band gap by using a mixed crystal of a material having a negative band gap and a material having a positive temperature dependency. As a material having a positive temperature dependence of the band gap, an HgCdTe mixed crystal and a III-V compound semiconductor mixed crystal containing Bi are known. The HgCdTe mixed crystal is liable to have crystal defects, and it is not easy to obtain a high-quality crystal. Actually, research is being conducted with the aim of realizing a current injection laser, but even room-temperature oscillation has not been reported. In fact, in a III-V compound semiconductor mixed crystal containing Bi, a crystal having a large Bi composition in which the temperature dependence of the band gap is positive is obtained because the immiscibility of the crystal is extremely large. Absent.

[0008]

SUMMARY OF THE INVENTION In view of the above-mentioned prior art, an object of the present invention is to provide a means for eliminating the temperature dependence of the emission wavelength of an optical semiconductor crystal and an optical semiconductor device manufactured using the same. As a first subject.

A second object is to provide means for controlling the degree of composition separation in a compound semiconductor mixed crystal.

[0010]

SUMMARY OF THE INVENTION The present invention has been made based on the following findings and considerations. That is, if the degree of compositional separation in a mixed crystal of a compound semiconductor such as InGaAsP increases, the temperature dependence of the band gap near room temperature changes from negative to positive.
The temperature dependence of the band gap disappears or becomes extremely small.

Therefore, if such a compound semiconductor whose composition is separated is used as an optical semiconductor crystal and an active layer of an optical semiconductor device manufactured using the same, the emission wavelength has no or no temperature dependence. The optical semiconductor crystal and the optical semiconductor element having an extremely small value are obtained.

Further, as the growth rate of a compound semiconductor such as InGaAsP is increased, the temperature dependence of the band gap near room temperature changes from negative to positive. This makes it possible to manufacture an optical semiconductor crystal and an optical semiconductor element having no or little temperature dependence of the emission wavelength.

The invention according to claim 1 of the present invention for solving the first problem is characterized in that an optical semiconductor crystal is provided with an active layer of a compound semiconductor whose composition is separated by immiscibility of the crystal. Optical semiconductor crystal.

According to a second aspect of the present invention, in the first aspect, the degree of the composition separation is set so that the band gap of the active layer has no temperature dependency.

A third aspect of the present invention is an optical semiconductor device manufactured by using the semiconductor crystal according to any one of the first and second aspects. According to a fourth aspect of the present invention, there is provided a method of manufacturing an optical semiconductor crystal, comprising a step of growing an active layer of a compound semiconductor compositionally separated by immiscibility of the crystal. It is.

According to a fifth aspect of the present invention for solving the above second problem, in the fourth aspect, the step of growing the active layer comprises controlling a growth rate.
It is characterized by a step of controlling the degree of composition separation.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic explanatory view of a cross section of an optical semiconductor crystal according to an embodiment of the present invention. As a typical example, an optical semiconductor crystal having an emission wavelength of 1.5 μm is shown.

This optical semiconductor crystal has a double hetero structure, and is formed on an n-type InP (100: Miller index) substrate 10 by using InGaAsP having a composition having an emission wavelength of 1.3 μm.
A light confinement layer 20, an InGaAsP active layer 30 having a composition of an emission wavelength of 1.5 μm, which is compositionally separated by immiscibility of a crystal, and InGa having a composition of an emission wavelength of 1.3 μm
AsP light confinement layer 40, p-type InP cladding layer 50,
Further, a p-type InGaAs electrode layer 60 is laminated in this order. InG having a composition with an emission wavelength of 1.5 μm
The point that the composition of the aAsP active layer is separated is different from the conventional one.

This optical semiconductor crystal is characterized in that the active layer is composed of an InGaAsP layer whose composition is separated. Conventionally, an InGaAsP layer without composition separation has been used as the active layer. The composition of the active layer has an emission wavelength of 1.5 μm.
The composition is not limited to m, but may be in the immiscible region in the phase diagram of the InGaAsP mixed crystal. Changing the composition of the light confinement layer according to the composition of the active layer is within the scope of those skilled in the art.

FIG. 2 shows the temperature dependence of the photoluminescence peak energy of the photosemiconductor crystal shown in FIG. The temperature dependence of the photoluminescence peak energy indicates the temperature dependence of the band gap.

The square plot in the figure indicates the temperature dependence when the active layer was grown at a growth rate of 4.6 (Å / sec), and the circle plot indicates the growth rate of 2.5 (Å / sec).
This is the case. Room temperature important for practical use (300K)
Focusing on the temperature dependence of the peak energy in the vicinity, in the case of a growth rate of 4.6 (Å / sec), the photoluminescence peak energy decreases with an increase in temperature, so the temperature dependence is negative. On the other hand, when the growth rate is 2.5 (Å / sec), the photoluminescence peak energy increases as the temperature increases, so that the temperature dependency is positive.

Therefore, according to FIG. 2, first of all,
It can be seen that the temperature dependence of the band gap near room temperature changes from negative to positive through zero depending on the growth rate of the active layer. This means that the temperature dependence of the band gap can be easily controlled by the growth rate. Second, it can be seen that by appropriately controlling the growth rate, the degree of compositional separation can be controlled and the temperature dependence of the band gap near room temperature can be eliminated.

Therefore, if an optical semiconductor device is manufactured using such an optical semiconductor crystal, the temperature dependence of the emission wavelength can be eliminated. In this embodiment, the case where the active layer is InGaAsP has been described.
The active layer is not limited to InGaAsP, but a mixed crystal semiconductor having an immiscible region in the phase diagram, for example, PInG
aAs, AlGaAs, InGaP, AlGaInP,
The present invention can be applied to other compound semiconductors such as GaAsSb, GaN, and InGaN, and similar effects can be obtained. Further, as a method of controlling the composition separation, it goes without saying that other methods such as temperature control may be used in addition to the method of controlling the growth rate.

In applications where the negative temperature dependence is positively utilized, conditions may be selected to further promote compositional separation. FIG. 3 is a schematic explanatory view showing a configuration example of a semiconductor laser as an example of an optical semiconductor device manufactured using the optical semiconductor crystal shown in FIG.

This semiconductor laser has a substrate 10 shown in FIG.
The upper laminated portion is formed in a mesa structure using a known manufacturing process, and Fe-doped InP 70 is provided on both sides thereof, and the lower surface of the substrate 10 and the p-type InGaAs electrode layer 6 are formed.
In this configuration, an n-type electrode 80 and a p-type electrode 81 are provided on each of the upper surfaces of 0.

The active layer of this semiconductor laser is made of InGaAs.
If sP is compositionally separated by the immiscibility of the crystal, and if the degree of this composition separation is set to a value that does not have the temperature dependence of the band gap, a semiconductor laser having no temperature dependence of the oscillation wavelength can be realized. It becomes possible. In addition,
This semiconductor laser is merely an example of an optical semiconductor device manufactured using the optical semiconductor crystal of FIG. Depending on the application, in the optical semiconductor crystal of FIG. 1, the n-type InP (100) substrate 10 and the 1.3 μm composition InGaAsP optical confinement layer 20 are used.
It is also possible to form a diffraction grating at the interface between the InGaAsP light confinement layer 40 and the p-type InP cladding layer 50 having a composition of 1.3 μm.

[0027]

As described above, according to the present invention,
Conventionally, as a cause of crystal deterioration, a compound semiconductor that has not been conventionally used, and has a compositionally separated compound semiconductor, is used as an active layer. An optical semiconductor device using this can be realized. Also,
By controlling the growth rate, it is also possible to control the degree of composition separation in the compound semiconductor mixed crystal.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a structure of a semiconductor crystal according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the temperature dependence of band gap energy.

FIG. 3 is a schematic explanatory view of a configuration example of a semiconductor laser manufactured using the optical semiconductor crystal shown in FIG.

[Explanation of symbols]

Reference Signs List 10 n-type InP (100) substrate 20 1.3 μm composition InGaAsP light confinement layer 30 1.5 μm composition InGaAsP active layer 40 with composition separation 40 1.3 μm composition InGaAsP light confinement layer 50 p-type InP cladding layer 60 p-type InGaAsP electrode layer 70 Fe-doped InP 80 n-type electrode 81 p-type electrode

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Manabu Manabu 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo F-term within Nippon Telegraph and Telephone Corporation (reference) 5F041 AA14 CA04 CA34 CA36 CA39 CA40 CA62 5F073 AA22 AA45 CA02 CA05 CA06 CA07 CA12 CA14 EA29 5F103 DD05 DD08 DD13 DD30 GG10 LL01 LL03 LL04 NN02 NN10 RR05

Claims (5)

[Claims] 1. An optical semiconductor crystal, comprising: an active layer of a compound semiconductor compositionally separated by immiscibility of the crystal. 2. The optical semiconductor crystal according to claim 1, wherein the degree of the compositional separation of the active layer is set so that the band gap of the active layer does not have a temperature dependency. 3. An optical semiconductor device manufactured using the optical semiconductor crystal according to claim 1. 4. A method for producing an optical semiconductor crystal, comprising a step of growing an active layer of a compound semiconductor compositionally separated due to immiscibility of the crystal. 5. The method for manufacturing an optical semiconductor crystal according to claim 4, wherein the step of growing the active layer is a step of controlling a degree of composition separation by controlling a growth rate.