JP2014225575A - Semiconductor laminate structure, surface emitting laser array and optical apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor laminate structure which can inhibit warpage of a substrate and inhibit deterioration in basic characteristics caused by increase in heat resistance and heat.SOLUTION: A semiconductor laminate structure of the present invention comprises: a semiconductor substrate; a semiconductor multilayer film arranged on the semiconductor substrate; a strain compensation layer arranged between the semiconductor substrate and the semiconductor multilayer film. The semiconductor multilayer film includes a stacked plurality of paired layers of a layer having first strain and a layer having second strain, in which a sum of the first strain and the second strain is a sum of compression strain or extensional strain and strain of the strain compensation layer has a sign opposite to a sign of the sum of the first strain and the second strain.

Description

  The present invention relates to a semiconductor multilayer structure, a surface emitting laser array, and an optical apparatus.

As one of surface emitting lasers, a vertical cavity surface emitting laser (VCSEL) is known. In this surface emitting laser, light can be extracted in a direction perpendicular to the surface of the semiconductor substrate, so that a two-dimensional array can be easily formed only by changing a mask pattern at the time of element formation.
Parallel processing using a plurality of beams emitted from the two-dimensional array enables high density and high speed, and various industrial applications are expected. For example, when a surface emitting laser array is used as an exposure light source of an electrophotographic printer, a printing process using a plurality of beams can be performed at high speed and with high definition.

Such a vertical cavity surface emitting laser (hereinafter referred to as a surface emitting laser) is composed of an active layer and at least a pair of multilayer reflectors sandwiching the active layer vertically.
The multilayer-film reflective mirror is configured by repeating pairs of two kinds of layers having different refractive indexes, and the thickness of each of these layers is an optical thickness that is ¼ of the oscillation wavelength.
Generally, a dielectric or a semiconductor is used as the multilayer film reflecting mirror. When a semiconductor is used in this way, a layer capable of passing a current can be formed by doping impurities while growing a crystal on a semiconductor substrate, and current injection into the active layer is facilitated.
However, since it is necessary to obtain a single crystal layer by crystal growth, the constituent layers of the multilayer semiconductor are limited to materials that lattice-match with the substrate.
In addition, in such a combination of lattice-matching semiconductors, the refractive index difference cannot be as large as when formed by a dielectric, so that a repetitive pair is required to obtain the reflectance necessary for oscillation of a surface emitting laser. It is necessary to increase the number.

As an example of a surface emitting laser that is actually put into practical use, there is an infrared surface emitting laser that oscillates in the 850 nm or 780 nm band.
The multilayer mirror is composed of a pair of an AlGaAs layer having a high Al composition and an AlGaAs layer having a low Al composition on a GaAs substrate.
AlGaAs has a slightly larger lattice constant than GaAs. For example, even when AlAs has the largest Al composition, the lattice mismatch with the GaAs substrate is 0.143%. Such a strain is generally regarded as a lattice-matched material, and the effect of strain is small.
However, in the surface emitting laser, it is necessary to stack several tens of pairs of multilayer reflectors. Therefore, even if a single layer has a small strain, the total accumulated layer thickness becomes extremely thick by repeating the single layer having the strain. For this reason, the accumulated distortion amount has a great influence.

Taking a red surface emitting laser that oscillates in the 680 nm band as an example, in this element, AlGaAs substantially lattice-matched on a GaAs substrate is used for the multilayer reflector. Since AlGaAs having an Al composition that does not absorb at the oscillation wavelength needs to be selected, examples of the combination include Al _0.5 Ga _0.5 As / Al _0.9 Ga _0.1 As and Al _0.5 Ga _{0. .5} As / AlAs is selected.
These multilayer mirrors have an average Al composition of 0.7 or more, which is larger than that of a surface emitting laser that oscillates in the infrared region. This is about 0.1% in terms of average strain.
In the 680 nm band, since the difference in refractive index between the two semiconductor materials constituting the multilayer mirror is small, it is necessary to increase the number of pairs in order to ensure the reflectance leading to oscillation.
Specifically, about 30 pairs are required on the side where light is extracted, and about 60 pairs are required on the side where light is not extracted, for a total thickness of approximately 10 μm.
In this case, the cumulative amount of strain, which is the cumulative amount of strain and the total thickness of the underlying layer, is a large value of 0.1% × 10 μm = 1% · μm.

The epitaxial wafer is warped due to the large amount of accumulated strain, but in the case of a 650 μm-thick GaAs substrate, it is estimated that the warp is up to a radius of curvature of 7 m.
Since the AlGaAs layer has a slightly larger lattice constant than the GaAs substrate, the epi-wafer warps in a convex shape.
A value of a radius of curvature of 7 m corresponds to the generation of a gap close to 70 μm at the center of a 3-inch wafer. Actually, when the warpage of the epi-wafer is measured, a gap of 70 to 80 μm is generated, and it is confirmed that the substrate warps in a convex shape due to the accumulated strain amount.
Thus, when the warp occurs in the epi-wafer, it becomes a cause of deviation during pattern alignment in the photolithography process.
Further, when a wafer heating process is required in the element manufacturing process, in-plane unevenness of the temperature distribution occurs, resulting in in-plane variations in processing.
As a result, there arises a problem that the yield in element formation is reduced. Furthermore, the influence on the reliability of the element due to the existence of the accumulated strain amount is also a major concern.

Several methods have been disclosed as solutions to such substrate warpage.
For example, Patent Document 1 discloses a method of selecting a material that compensates for distortion between pairs of multilayer reflectors.
In this disclosed method, when a layer having compressive strain such as AlGaAs on a GaAs substrate is selected as one layer of the pair, a method using a layer having tensile strain is used for the remaining layer. Taken.
Specifically, since the thickness of the constituent layer of the multilayer mirror is adjusted to an optical thickness that is ¼ of the oscillation wavelength, the layer thickness differs according to the magnitude of the refractive index, In the case of a semiconductor material, since the refractive index difference is not so large, each layer thickness is almost equal.
For example, in the case of a red surface emitting laser, the ¼ optical thickness of the oscillation wavelength is approximately 50 nm.
Therefore, in order to compensate for the distortion, in the layers constituting the pair, the absolute values of the respective distortions are approximately equal. Thus, in Patent Document 1, by taking distortions whose signs, that is, directions are opposite to each other, The pair compensates for distortion.

JP 2006-310534 A

However, the method of selecting a material that compensates for distortion between pairs as in Patent Document 1 of the conventional example has the following problems.
That is, it is not always sufficient to simply provide a layer having substantially the same value and opposite signs as in the conventional example.
It is desired that the layer constituting the semiconductor multilayer structure is a material that does not absorb at the oscillation wavelength, can ensure a sufficient difference in refractive index, and exhibits good electrical conductivity by doping.
As a material that satisfies these conditions at the same time, a binary compound (mixed crystal semiconductor) or a ternary mixed crystal semiconductor is limited.

These will be further described below. FIG. 5 is a schematic diagram illustrating the relationship between the refractive index and the lattice constant in binary, ternary and quaternary mixed crystal semiconductors.
In FIG. 5, the vertical axis indicates the refractive index, and the horizontal axis indicates the strain with respect to the GaAs substrate. Here, a strain having a positive sign is a tensile strain, and a strain having a negative sign is a compressive strain.
As shown in FIG. 5, the binary compound has a refractive index and a strain that have a point relationship and is uniquely determined.
Even in the case of a ternary mixed crystal semiconductor, the refractive index and the strain are in a line relationship and cannot be controlled independently. When a quaternary or more mixed crystal semiconductor is used, the refractive index and the strain are in a plane relationship for the first time, and each can be controlled independently.
However, when a quaternary or higher mixed crystal semiconductor is used, the refractive index and strain can be controlled independently, but the thermal resistance increases as compared with binary compounds and ternary mixed crystal semiconductors.
Therefore, when a mixed crystal semiconductor of quaternary or higher is applied to the multilayer film reflector and arranged adjacent to the active region, heat dissipation is hindered and the element internal temperature rises, and the element characteristics are lowered accordingly. .

  In view of the above-described problems, an object of the present invention is to provide a semiconductor multilayer structure that can suppress warping of a substrate, increase thermal resistance, and suppress deterioration of basic characteristics of an element due to heat.

The semiconductor multilayer structure of the present invention includes a semiconductor substrate, a semiconductor multilayer film disposed on the semiconductor substrate, and a strain compensation layer disposed between the semiconductor substrate and the semiconductor multilayer film. In the semiconductor multilayer film, a plurality of pair layers of a layer having a first strain and a layer having a second strain are stacked, and a sum of the first strain and the second strain is compressed. The strain of the strain compensation layer has a sign opposite to the sum of the first strain and the second strain.
Another semiconductor laminated structure of the present invention is a semiconductor substrate, a semiconductor multilayer film disposed on the semiconductor substrate, and a surface facing the surface side of the semiconductor substrate on which the semiconductor multilayer film is disposed. A semiconductor multilayer structure having a strain compensation layer disposed on the side, wherein the semiconductor multilayer structure layer is formed by laminating a plurality of pair layers of a layer having a first strain and a layer having a second strain, A sum of the first strain and the second strain is a sum of compressive or tensile strains, and the strain of the strain compensation layer is the strain of the first strain and the second strain. It is the same sign as the sum.

  ADVANTAGE OF THE INVENTION According to this invention, the semiconductor laminated structure which can suppress the curvature of a board | substrate and can suppress the increase in thermal resistance and the deterioration of the basic characteristic of an element by a heat | fever can be implement | achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic cross-sectional view for explaining a configuration example of a vertical cavity surface emitting laser in Example 1 of the present invention. The conceptual diagram which shows the relationship between the refractive index in the binary compound in Example 1 of this invention, a ternary, and a quaternary mixed crystal semiconductor, and the distortion with respect to a GaN board | substrate. Sectional schematic diagram for demonstrating the structural example of the vertical cavity surface emitting laser in Example 2 of this invention. Schematic for demonstrating the optical apparatus (electrophotographic recording type image forming apparatus) provided with the surface emitting laser array comprised by the vertical cavity surface emitting laser in Example 3 of this invention as a light source. The conceptual diagram which shows the relationship between the refractive index and the distortion with respect to a GaAs substrate in a binary compound, a ternary, and a quaternary mixed crystal semiconductor for demonstrating the technical subject of this invention.

Next, a configuration example in the embodiment of the present invention will be described.
The semiconductor multilayer structure of the present embodiment has a semiconductor multilayer film on a semiconductor substrate, and is stable by inserting a strain compensation layer composed of a pair of quaternary or more mixed crystal semiconductors in a region away from the active layer. It is possible to suppress the warpage of the substrate with good reproducibility. In addition, according to this, it is possible to prevent an increase in thermal resistance and suppress deterioration of the basic characteristics of the element due to heat.
Specifically, for example, when suppressing warpage of a substrate and suppressing deterioration of element characteristics due to heat, unlike the conventional example, the following semiconductor stacked structure using a strain compensation layer is configured.
That is, this semiconductor multilayer structure includes a semiconductor multilayer film disposed on a semiconductor substrate, and a strain compensation layer disposed between the semiconductor substrate and the semiconductor multilayer film.
At that time, the semiconductor multilayer film is formed by stacking a plurality of pair layers of a layer having a first strain and a layer having a second strain.
The sum of the first strain and the second strain is the sum of compressive or tensile strains.
The strain of the strain compensation layer is
The sign is opposite to the sum of the first distortion and the second distortion.
The strain compensation layer is formed by stacking a plurality of pair layers of a third strain layer and a fourth strain layer, and the sum of the third strain and the fourth strain is the first strain and the second strain. It is comprised so that it may become a code | symbol opposite to the sum of distortion of.
Further, as a form different from the above form, the semiconductor multilayer structure has a semiconductor multi-layer film disposed on a semiconductor substrate and a strain disposed on the surface side of the semiconductor substrate opposite to the surface side on which the semiconductor multi-layer film is disposed. A configuration having a compensation layer can be employed.
The strain of the strain compensation layer at this time has the same sign as the sum of the first strain and the second strain.
The strain compensation layer is formed by stacking a plurality of pair layers of a third strain layer and a fourth strain layer, and the sum of the third strain and the fourth strain is the first strain and the second strain. It is comprised so that it may become the same code | symbol as the sum of distortion.
In any form, the absolute value of the sum of the third distortion and the fourth distortion is larger than the absolute value of the sum of the first distortion and the second distortion.

With the above configuration, it is possible to suppress the warpage of the substrate, and it is possible to obtain a semiconductor multilayer structure that can suppress the deterioration of the basic characteristics of the element due to heat.
Note that the semiconductor stacked structure may have an active layer. In particular, the semiconductor laminated structure having an active layer has an upper reflecting mirror and a lower reflecting mirror disposed on the semiconductor substrate so as to face each other with the active layer interposed therebetween, and at least one of the upper reflecting mirror and the lower reflecting mirror is provided. It is possible to obtain a surface emitting laser composed of a semiconductor multilayer film.
In addition, a surface emitting laser array can be configured by arranging a plurality of such surface emitting lasers.
Moreover, it becomes possible to constitute an optical apparatus provided with such a surface emitting laser array as a light source.

Examples of the present invention will be described below.
[Example 1]
In the first embodiment, a case will be described in which a strain compensation layer is formed between a semiconductor substrate and a semiconductor multilayer mirror.
Further, in Example 1, a vertical cavity surface emitting laser that oscillates at 680 nm, which is a semiconductor multilayer structure composed of semiconductor multilayer reflectors disposed opposite to each other across an active layer on a GaAs semiconductor substrate. The configuration of will be described.
Here, the reflecting mirror close to the semiconductor substrate is the lower reflecting mirror.

FIG. 1 is a schematic diagram for explaining the configuration of a vertical cavity surface emitting laser according to this embodiment.
100 is an n-type GaAs substrate, 102 is an n-type strain compensation layer, 104 is an n-type semiconductor multilayer reflector, 106 is an n-type spacer layer, 108 is a quantum well active layer, 110 is a p-type spacer layer, and 112 is a p-type This is a semiconductor multilayer mirror.
Also, 114 is a p-type contact layer, 116 is a current confinement portion (oxidized region), 118 is a current confinement portion (selective oxide layer, non-oxidized region), 120 is an insulating layer, 122 is a p-side electrode, and 124 is an n-side Electrode.

The surface emitting laser of this example is obtained by using 38 pairs of n-type Al _0.1 on a (100) GaAs off-substrate 100 tilted by 10 degrees in the n-type (111) A plane direction using MOCVD crystal growth technology. Ga _0.5 In _0.4 P / Al _0.15 Ga _0.5 In _0.35 P strain compensation layer 102, 60 pairs of n-type Al _0.5 Ga _0.5 As / AlAs semiconductor multilayer reflector 104 Grow.
Further, an n-type AlGaInP spacer layer 106 and a GaInP / AlGaInP quantum well active layer 108 are sequentially grown thereon. Then, a p-type AlGaInP spacer layer 110 and a p-type Al _0.98 Ga _0.02 As selective oxide layer 118 are grown on the quantum well active layer 108. Further, 35 pairs of p-type Al _0.5 Ga _0.5 As / Al _0.9 Ga _0.1 As semiconductor multilayer mirror 112 and p-type GaAs contact layer 114 are grown thereon.

Next, the distortion that occurs in the n-type and p-type semiconductor multilayer mirrors will be described.
In an n-type multilayer mirror, an Al _0.5 Ga _0.5 As layer that is a high refractive index layer and an AlAs layer that is a low refractive index layer alternately have an optical thickness of ¼ of the oscillation wavelength. It consists of 60 pairs of repetitions. In addition, the p-type semiconductor multilayer mirror has an Al _0.5 Ga _0.5 As layer that is a high refractive index layer and an Al _0.9 Ga _0.1 As layer that is a low refractive index layer alternately oscillating. It consists of 35 pairs of repetitions with an optical thickness of 1/4 wavelength. Table 1 below shows the distortion of each layer constituting the semiconductor multilayer film reflecting mirror in this example with respect to the GaAs substrate and the optical thickness of ¼ of the oscillation wavelength (680 nm). Here, a strain having a positive sign is a tensile strain, and a strain having a negative sign is a compressive strain.

[Table 1]

Although the distortion of each layer constituting the n-type and p-type semiconductor multilayer reflector with respect to the GaAs substrate is slight, in the semiconductor multilayer reflector, the total accumulated layer thickness becomes extremely thick due to repetition of each layer. The amount of distortion is large.

Next, the amount of accumulated strain of each of the n-type (60 pairs) and p-type (35 pairs) semiconductor multilayer mirrors is estimated. The accumulated distortion amount can be obtained by the following equation.

Cumulative strain (μ%) = (thickness of constituent layer) x (strain of constituent layer) x (number of repetitions of constituent layer)

When the values of the respective layers shown in Table 1 are substituted into the above formula, the accumulated strain amount of each semiconductor multilayer film reflecting mirror becomes the values shown in the following Table 2.
[Table 2]

As shown in Table 2, the total accumulated strain amount of the n-type and p-type semiconductor multilayer mirrors is a large value of −1.04 μm ·%.
When a surface emitting laser having a semiconductor multilayer film reflecting mirror having such a cumulative strain amount as a constituent element is formed on a 650 μm thick GaAs substrate, it warps with a convex shape of about 70 μm at the center of the wafer. .

Next, a distortion compensation layer that compensates for distortion generated by the n-type and p-type semiconductor multilayer mirrors will be described.
By constructing the strain compensation layer so as to cancel out the large amount of accumulated strain generated by the n-type and p-type semiconductor multilayer mirrors as described above, the amount of accumulated strain in the entire wafer is suppressed, and the warpage of the substrate is suppressed. It becomes possible to solve the problem.
At this time, if the accumulated strain amount in the entire wafer can be reduced to zero μm ·%, the occurrence of warpage of the substrate can be suppressed.
On the other hand, even if the accumulated strain amount in the entire wafer is not reduced to zero μm ·%, for example, an epitaxial multilayer of 0.68 μm ·% cancels the accumulated strain amount −0.68 μm ·% generated by the n-type semiconductor multilayer mirror. Even in the case of forming a film, the warpage of the substrate can be suppressed to about 1/3, which is effective in suppressing a decrease in yield in element formation.

For example, by 35 pairs form the _{n-Al 0.1 Ga 0.5 In 0.4} P / Al 0.15 Ga 0.5 In 0.35 P as an epitaxial multilayer film, the cumulative amount of distortion in the whole wafer Can be made almost zero, and by forming 23 pairs, it becomes possible to cancel the accumulated strain produced by the n-type semiconductor multilayer mirror.
The thickness of each layer constituting the strain compensation layer in this case and the strain on the GaAs substrate are shown in Table 3 below.
Note that the accumulated strain amount generated by the n-type and p-type semiconductor multilayer mirrors of the present embodiment has a negative sign (compressibility), so the accumulated strain amount of the epitaxial multilayer film for canceling the strain amount is a positive sign ( Tensile properties).
On the other hand, when the accumulated strain amount generated by the n-type and p-type semiconductor multilayer mirrors has a positive sign (tensile property), the accumulated strain amount of the strain compensation layer has a negative sign (compressibility).

From Table 1 and Table 3, the absolute value of the sum of the third strain (for example, 0.55 (%)) and the fourth strain (1.1 (%)) is the first strain (for example, It can be seen that it is larger than the absolute value of the sum of −0.0716 (%)) and the second distortion (for example, −0.143 (%)).
The absolute value of the third strain (for example, 0.55 (%)) is the first strain (for example, -0.0716 (%)) and the second strain (for example, -0.143 (%)). It turns out that it is larger than any absolute value.
The absolute value of the fourth strain (1.1 (%)) is either the first strain (for example, -0.0716 (%)) or the second strain (for example, -0.143 (%)). It can be seen that it is larger than the absolute value of.
[Table 3]

Since the n-type semiconductor multilayer mirror having the reflectance necessary for laser oscillation is formed on the strain compensation layer, the strain compensation layer does not need to be a reflector and can be epitaxially grown. What is necessary is just to be comprised by thickness.
In this example, in order to obtain a layer having good crystallinity, the strain amount of each layer (the layer having the third strain and the layer having the fourth strain) is set to 0.02 μm ·% or less. The thickness of each layer is set.
In this embodiment, the thickness of each layer is set to 0.018 μm. However, the thickness is not limited to this, and it is not necessary that the thickness of each layer is the same.
For example, if the Al _0.1 Ga _0.5 In _0.4 P layer thickness in Table 3 is 0.036 μm, 26 pairs are formed. As a result, the absolute value of the accumulated strain amount of the n-type and p-type semiconductor multilayer mirror and the absolute value of the accumulated strain amount of the strain compensation layer can be made substantially equal, and the accumulated strain amount in the entire wafer can be made substantially zero.
The accumulated strain amount ε of the strain compensation layer can be obtained by the following equation.

ε = (ε ₃ × d ₃ × n ₃ ) + (ε ₄ × d ₄ × n ₄ )

However,
ε ₃ : third strain amount, d ₃ : layer thickness of the third strain layer, n ₃ : number of layers of the third strain layer ε ₄ : fourth strain amount, d ₄ : of the fourth strain layer Layer thickness, n ₄ : number of fourth strain layers

In the present embodiment, the absolute value of the accumulated strain amount ε of the strain compensation layer obtained by the above formula is at least 0.25 μm ·%.

In addition, the composition ratio of Al, Ga, In, and P of the quaternary mixed crystal semiconductor is not limited to that shown in Table 3, but may be a composition ratio that generates tensile strain on the GaAs substrate. It ’s fine. In that case, it is more preferable to select the layer thickness and the strain on the GaAs substrate so that the strain amount of each layer is 0.02 μm ·% or less.
In addition, the AlGaInP mixed crystal, which is a quaternary mixed crystal semiconductor used in this example, is particularly difficult to be p-type due to the influence of mixed crystal scattering.
On the other hand, since AlGaInP mixed crystals can obtain good n-type conduction by doping Si, the strain compensation layer is n-type and formed on an n-type GaAs substrate.

As shown in FIG. 1, the p-type Al _0.5 Ga _0.5 As / Al _0.9 Ga _0.1 As semiconductor multilayer mirror 112 has a p-type Al _0.9 close to the quantum well active layer 108. One of the Ga _0.1 As low refractive index layers is replaced with a p-type Al _0.98 Ga _0.02 As selective oxidation layer 118.
This layer is selectively oxidized in a high-temperature steam atmosphere and insulated from the periphery of the element, thereby forming a current confinement structure 116 in which a current flows only in the central portion.
The 108 quantum well active layers have a multiple quantum well structure composed of a plurality of GaInP quantum well layers and a plurality of AlGaInP barrier layers. The layer thicknesses of the n-type AlGaInP spacer layer 106 and the p-type AlGaInP spacer layer 110 are adjusted so that the multiple quantum well structure is positioned at the antinode of the internal optical standing wave. For the resonator constituted by these, the layer thickness is adjusted so as to have an optical thickness that is an integral multiple of the wavelength with respect to the oscillation wavelength of 680 nm.

The emission wavelength of the active layer itself is fabricated so as to have an emission peak wavelength (for example, 660 to 670 nm) on the shorter wavelength side than the resonance wavelength of the surface emitting laser resonator.
After forming the mesa structure, a current confinement structure is formed by steam oxidation, an insulating film 120 is deposited, and patterning is performed again to expose a part of the p-type GaAs contact layer 114, and a ring-shaped Ti / Au is formed thereon. The p-side electrode 122 is formed by vapor deposition.
Thereafter, the substrate is polished as necessary, AuGe / Ni / Au is vapor-deposited on the back surface of the n-type GaAs substrate 100, and annealed at around 400 ° C. to form the n-side electrode 124.
Finally, the chip is cut into a required size, die-bonded to the package, and the p-side electrode is wire-bonded to complete the device.
In addition, by appropriately designing the photomask for the array, not only a single element but also an array in which a plurality of elements are two-dimensionally arranged can be manufactured. Thus, the advantage of the surface emitting laser is that the array structure can be obtained relatively easily by changing only the photomask.

According to the configuration of this embodiment described above, it is possible to suppress an increase in the thermal resistance of the element while eliminating the warp of the substrate, and it is possible to form an element with little deterioration in characteristics due to heat with a high yield.
In this embodiment, a vertical cavity surface emitting laser oscillating at 680 nm formed on a GaAs substrate has been described. Therefore, although an AlGaInP layer is used as a quaternary or more mixed crystal semiconductor layer, a band gap (refractive index) and Any quaternary or higher mixed crystal semiconductor layer whose lattice constant can be controlled independently (for example, AlGaInPAs or AlGaInPAsN) may be used.
The contents described in this embodiment are also applicable to vertical cavity surface emitting lasers such as 780 nm band, 850 nm band, and 1300 nm band formed on a GaAs substrate.
In addition, as shown in FIG. 2, when a quaternary mixed crystal semiconductor such as AlGaInN is used, this embodiment also explains a GaN-based vertical cavity surface emitting laser having a shorter wavelength band formed on a GaN substrate. The contents can be applied.
In this embodiment, the n-type and p-type semiconductor multilayer film reflecting mirrors are employed as the upper reflecting mirror and the lower reflecting mirror of the surface emitting laser. However, the present invention is not limited to this. For example, a dielectric multilayer film or a photonic crystal mirror may be employed as the upper reflector. In this case, if the lower reflector is a semiconductor multilayer reflector, the contents described in this embodiment are applicable. .
Further, although the surface emitting laser is described in this embodiment, a semiconductor multilayer film such as a resonator type light emitting diode (RCLED) having an active layer having a structure similar to that of the surface emitting laser and a semiconductor multilayer film is used. The contents described in this embodiment can be applied to the semiconductor stacked structure.

[Example 2]
In the second embodiment, unlike the first embodiment, a case where the strain compensation layer is formed in contact with the substrate surface opposite to the surface on which the semiconductor multilayer mirror is formed will be described.
This embodiment is an effective technique for suppressing the warpage of the substrate when it is not necessary to polish the substrate.

FIG. 3 is a schematic diagram for explaining the configuration of a vertical cavity surface emitting laser according to the present invention.
200 is an n-type GaAs substrate, 202 is an n-type strain compensation layer, 204 is an n-type semiconductor multilayer reflector, 206 is an n-type spacer layer, 208 is a quantum well active layer, 210 is a p-type spacer layer, and 212 is a p-type This is a semiconductor multilayer mirror.
214 is a p-type contact layer, 216 is a current confinement portion (oxidized region), 218 is a current confinement portion (selective oxide layer, non-oxidized region), 220 is an insulating layer, 222 is a p-side electrode, and 224 is an n-side. Electrode.

Hereinafter, differences from the first embodiment will be described.
Although described in the first embodiment, the points not described below are the same in the second embodiment.
The amount of distortion generated by the n-type 204 and p-type 212 semiconductor multilayer mirror is as described in the first embodiment.
On the other hand, unlike the first embodiment, the strain compensation layer 202 is disposed on the surface opposite to the surface on which the semiconductor multilayer mirror disposed on the semiconductor substrate is disposed. The strain amount generated by the p-type semiconductor multilayer mirror 212 and the strain amount generated by the strain compensation layer 202 have the same sign.
In the case of a vertical cavity surface emitting laser in the 680 nm band as in the first embodiment, the accumulated strain amount generated by the n-type 204 and p-type 212 semiconductor multilayer reflectors is the same.
On the other hand, the distortion compensation _layer, an _{n-Al 0.1 Ga 0.25 In 0.65} P / Al 0.1 Ga 0.35 In 0.55 P by 35 pair formation, cumulative distortion for the entire wafer The amount can be made almost zero, and by forming 23 pairs, it becomes possible to cancel the accumulated strain amount generated by the n-side semiconductor multilayer mirror.
Table 4 below shows the relationship between the thickness of the n-type semiconductor layer constituting the strain compensation layer and the strain on the GaAs substrate.
Note that the accumulated strain amount generated by the n-type and p-type semiconductor multilayer mirrors of this embodiment has a negative sign (compressibility), so the accumulated strain amount of the strain compensation layer for canceling the strain amount is a negative sign ( Compressibility).
On the other hand, when the accumulated strain amount generated by the n-type and p-type semiconductor multilayer mirrors is a plus sign (tensile property), the accumulated strain amount of the strain compensation layer becomes a plus sign (tensile property).
[Table 4]

  According to the configuration of the present embodiment described above, an increase in the thermal resistance of the element can be suppressed while eliminating the warpage of the substrate, and an element with less characteristic deterioration due to heat can be formed with a high yield.

[Example 3]
As a third embodiment, a surface emitting laser array in which the vertical cavity surface emitting lasers described in the first and second embodiments are arranged in an array using FIG. 4 is provided as a light source. A configuration example of the optical apparatus will be described.
Here, a configuration example of an image forming apparatus configured using a laser array using the surface emitting laser as an optical apparatus will be described.
4A is a plan view of the image forming apparatus, and FIG. 4B is a side view of the apparatus.
In FIG. 4, reference numeral 2000 denotes a photosensitive drum (photoconductor), 2002 denotes a charger, 2004 denotes a developing unit, 2006 denotes a transfer charger, 2008 denotes a fixing unit, 2010 denotes a rotating polygon mirror, and 2012 denotes a motor.
Reference numeral 2014 denotes a surface emitting laser array, 2016 denotes a reflecting mirror, 2018 denotes a collimator lens, and 2020 denotes an f-θ lens.
In this embodiment, the rotary polygon mirror 2010 is rotationally driven by a motor 2012 shown in FIG. 4B.
The surface emitting laser array 2014 serves as a recording light source, and is configured to be turned on or off according to an image signal by a laser driver (not shown).

The laser light thus modulated is irradiated from the surface emitting laser array 2014 to the rotary polygon mirror 2010 via the collimator lens 2018.
The rotating polygon mirror 2010 rotates in the direction of the arrow, and the laser light output from the surface emitting laser array 2014 is reflected as a deflected beam that continuously changes the emission angle on the reflecting surface as the rotating polygon mirror 2010 rotates. Is done.
The reflected light is subjected to correction of distortion and the like by the f-θ lens 2020, irradiated to the photosensitive drum 2000 through the reflecting mirror 2016, and scanned on the photosensitive drum 2000 in the main scanning direction. At this time, images of a plurality of lines corresponding to the surface emitting laser array 2014 are formed in the main scanning direction of the photosensitive drum 2000 by the reflection of the beam light through one surface of the rotating polygon mirror 2010.
The photosensitive drum 2000 is charged in advance by a charger 2002 and sequentially exposed by scanning with a laser beam to form an electrostatic latent image.
Further, the photosensitive drum 2000 is rotated in the direction of the arrow, and the formed electrostatic latent image is developed by the developing device 2004, and the developed visible image is transferred to the transfer paper by the transfer charger 2006.
The transfer paper on which the visible image is transferred is conveyed to a fixing device 2008, and after fixing, the transfer paper is discharged out of the apparatus.

In the above description, an example in which an image forming apparatus is configured as an optical apparatus has been described. However, the present invention is not limited to such a configuration.
For example, the laser array of the present invention is used as a light source, and an image display body and an optical deflector are used, and light obtained by deflecting light from the light source by the optical deflector is incident on the image display body. A projection display may be configured as possible.

100: n-type GaAs substrate 102: n-type strain compensation layer 104: n-type semiconductor multilayer reflector 106: n-type spacer layer 108: quantum well active layer 110: p-type spacer layer 112: p-type semiconductor multilayer reflector 114 : P-type contact layer 116: current constriction (oxidized region)
118: Current confinement portion (selective oxide layer, non-oxidized region)
120: Insulating layer 122: p-side electrode 124: n-side electrode

Claims (17)

A semiconductor multilayer structure comprising: a semiconductor substrate; a semiconductor multilayer film disposed on the semiconductor substrate; and a strain compensation layer disposed between the semiconductor substrate and the semiconductor multilayer film,
The semiconductor multilayer film is formed by laminating a plurality of pair layers of a layer having a first strain and a layer having a second strain, and the sum of the first strain and the second strain is compressive or tensile. Having a configuration that is the sum of the distortions of
The semiconductor multilayer structure, wherein the strain of the strain compensation layer has a sign opposite to a sum of the first strain and the second strain.   The strain compensation layer includes a plurality of pairs of a layer having a third strain and a layer having a fourth strain, and the sum of the third strain and the fourth strain is the first strain. The semiconductor multilayer structure according to claim 1, wherein the semiconductor multilayer structure has a sign opposite to that of the sum of the second distortion and the second distortion. A semiconductor having a semiconductor substrate, a semiconductor multilayer film disposed on the semiconductor substrate, and a strain compensation layer disposed on a surface side of the semiconductor substrate opposite to a surface side on which the semiconductor multilayer film is disposed A laminated structure,
In the semiconductor multilayer film constituting layer, a plurality of pair layers of a layer having a first strain and a layer having a second strain are stacked, and the sum of the first strain and the second strain is compressive or tensile. Having a configuration that is the sum of sex distortion,
The semiconductor multilayer structure, wherein the strain of the strain compensation layer has the same sign as the sum of the first strain and the second strain.   The strain compensation layer includes a plurality of pairs of a layer having a third strain and a layer having a fourth strain, and the sum of the third strain and the fourth strain is the first strain. The semiconductor multilayer structure according to claim 3, wherein the same sign as that of the sum of the second distortion and the second distortion is used. The semiconductor substrate is GaAs;
The semiconductor multilayer film is composed of a binary semiconductor material composed of Ga, As constituent elements, or a ternary semiconductor material composed of Al, Ga, As constituent elements,
The sum of the first strain and the second strain is compressive,
5. The semiconductor multilayer structure according to claim 1, wherein the layer constituting the strain compensation layer is a quaternary or more mixed crystal semiconductor containing Al, Ga, In, and P. 6. The semiconductor substrate is GaN;
The semiconductor multilayer film constituting layer is composed of a binary semiconductor material composed of Ga, N constituent elements or a ternary semiconductor material composed of Al, Ga, N constituent elements,
The sum of the first strain and the second strain is tensile,
5. The semiconductor multilayer structure according to claim 1, wherein the layer constituting the strain compensation layer is a quaternary or more mixed crystal semiconductor containing Al, Ga, In, and N. 6.   The absolute value of the sum of the third strain and the fourth strain is larger than the absolute value of the sum of the first strain and the second strain. The semiconductor laminated structure according to item.   7. The semiconductor multilayer structure according to claim 1, wherein an absolute value of the third strain is larger than any one of the first strain and the second strain. .   7. The semiconductor multilayer structure according to claim 1, wherein an absolute value of the fourth strain is larger than any one of the first strain and the second strain. .   The semiconductor multilayer structure according to claim 1, wherein an absolute value of the third strain amount or the fourth strain amount is 0.02 μm ·% or less.   11. The semiconductor multilayer structure according to claim 1, wherein the accumulated strain amount ε of the strain compensation layer has an absolute value of at least 0.25 μm ·% or more.   12. The semiconductor multilayer structure according to claim 1, wherein the absolute value of the total cumulative strain amount in the semiconductor multilayer structure is substantially equal to the absolute value of the cumulative strain amount of the strain compensation layer. .   13. The semiconductor multilayer structure according to claim 1, wherein the layer having the third strain and the layer having the fourth strain are formed of an n-type semiconductor.   The semiconductor multilayer structure according to claim 1, further comprising an active layer disposed on the semiconductor substrate. The semiconductor multilayer structure according to claim 14,
A surface-emitting laser having an upper reflecting mirror and a lower reflecting mirror disposed opposite to each other across the active layer on the semiconductor substrate;
At least one of the upper reflecting mirror and the lower reflecting mirror is composed of the semiconductor multilayer film.   A surface emitting laser array comprising a plurality of the semiconductor laminated structures according to claim 15 arranged in an array.   An optical apparatus comprising the surface emitting laser array according to claim 16 as a light source.