JP2019169601A - Infrared light emitting element - Google Patents

Abstract

To provide an infrared light emitting element with improved light emission characteristics.SOLUTION: The infrared light emitting element according to the present invention includes a substrate 1, an n-type contact layer 2 formed on the substrate 1, a first barrier layer 3 having an n-type conductivity formed on the n-type contact layer including a compound semiconductor layer containing Al, In, As, and Sb, and an active layer 4 formed on the n-type barrier layer 3 containing a compound semiconductor layer including InAsSb(0≤x≤1), and a second barrier layer 5 formed on the active layer 4 including a compound semiconductor layer containing Al, Ga, As, and Sb.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an infrared light emitting device.

  An infrared light emitting element (LED: Light Emitting Diode) forms a so-called pn junction diode structure in a semiconductor having a band gap capable of emitting infrared light of a specific wavelength. The infrared light emitting element emits infrared light by flowing a forward current through the pn junction diode and recombining electrons and holes in a depletion layer at the junction.

  In Patent Document 1, in an infrared light emitting device including an n-type compound semiconductor layer and a p-type doped π layer, an n-type compound semiconductor layer and a π layer are provided between the n-type compound semiconductor layer and the π layer. Also, it is described that an n-type wide band gap layer having a large band gap is provided. This suppresses diffusion of holes generated by thermal excitation at room temperature in the n-type compound semiconductor layer in the direction of the π layer, reduces dark current of the pn diode due to holes, and generates by thermal excitation on the π layer side. The diffusion of the formed holes into the n-type compound semiconductor layer is also suppressed. The technique of Patent Document 1 realizes an infrared light emitting element with a high diode resistance in which the diffusion current of the pn diode is also reduced.

International Publication No. 2009/113585

  Infrared light emitting elements are required to have improved light emission characteristics, but the infrared light emitting elements described in Patent Document 1 have room for improvement in this respect.

  An object of the present invention is to provide an infrared light emitting device having improved light emitting characteristics.

The infrared light emitting device of the present invention includes a substrate, an n-type contact layer formed on the substrate and including at least In, As, and Sb, and formed on the n-type contact layer, and includes Al, In, As, and Sb. A first barrier layer including at least an n-type conductivity; an active layer formed on the first barrier layer and including InAs _x Sb _(1-x) (0 ≦ x ≦ 1); and the active layer And a second barrier layer containing at least Al, Ga, As, and Sb.

The infrared light emitting device of the present invention includes a substrate, a p-type contact layer formed on the substrate, and a second barrier layer formed on the p-type contact layer and including at least Al, Ga, As, and Sb. And an active layer formed on the second barrier layer and containing InAs _x Sb _(1-x) (0 ≦ x ≦ 1), and formed on the active layer and containing at least Al, In, As, and Sb. And a first barrier layer having an n-type conductivity type and an n-type contact layer formed on the first barrier layer and including at least In, As, and Sb.

  According to the infrared light emitting device of the first and second embodiments of the present invention, an infrared light emitting device having improved light emission characteristics can be obtained.

It is sectional drawing which shows the structure of the infrared rays light emitting element of a 1st aspect. It is sectional drawing which shows the structure of the infrared rays light emitting element of a 2nd aspect. It is sectional drawing which shows the structure of the infrared rays light emitting element of 1st embodiment. It is sectional drawing which shows the structure of the infrared rays light emitting element of 2nd embodiment.

  In the following detailed description, numerous specific specific configurations are described to provide a thorough understanding of embodiments of the invention. However, it will be apparent that other embodiments may be practiced without limitation to such specific specific configurations. Further, the following embodiments do not limit the invention according to the claims, but include all combinations of characteristic configurations described in the embodiments.

[First aspect]
<Configuration>
As shown in FIG. 1, the infrared light emitting device of the first aspect includes a substrate 1, an n-type contact layer 2 formed on one surface (on the substrate) of the substrate 1, and a substrate of the n-type contact layer 2. The first barrier layer 3 having n-type conductivity formed on the opposite surface (on the n-type contact layer) and the surface of the first barrier layer 3 opposite to the n-type contact layer 2 (first barrier layer) And the second barrier layer 5 formed on the surface of the active layer 4 opposite to the first barrier layer 3 (on the active layer). The first barrier layer 3 having n-type conductivity includes a compound semiconductor layer containing Al, In, As, and Sb. The active layer 4 includes a compound semiconductor layer containing InAs _x Sb _(1-x) (0 ≦ x ≦ 1). The second barrier layer 5 includes a compound semiconductor layer containing Al, Ga, As, and Sb.

  Here, the term “on” in the expression “an n-type contact layer formed on a substrate and containing at least In, As, and Sb” means that an n-type contact layer is formed on the substrate. This means that the expression includes a case where another layer is further present between the substrate and the n-type contact layer. In the relationship between other layers, the word “upper” has the same meaning.

In addition, here, the phrase “including” in the expression “active layer including InAs _x Sb _(1-x) (0 ≦ x ≦ 1)” means that In, As, and Sb are mainly included in the layer. However, the expression includes other elements. Specifically, this expression also includes cases where minor changes are made to the composition of this layer by adding a small amount of other elements (for example, elements of Al, P, Ga, N, etc., several percent or less). Is natural. In the expression of the composition of other layers, the word “including” has the same meaning.

<Action, effect>
According to the infrared light emitting device of the first aspect, the second barrier layer containing at least Al, Ga, As and Sb, the first barrier layer containing at least Al, In, As and Sb and having n-type conductivity, The band offset (ΔEc) of the conductor between the active layer (light absorption layer) and the second barrier layer, and the band of the valence band between the active layer and the first barrier layer having the n-type conductivity type. Each offset (ΔEv) can be sufficiently increased.

  Thereby, the barrier function by the 1st barrier layer and the 2nd barrier layer is improving the infrared light emitting element of the 1st mode. That is, according to the first aspect of the present invention, an infrared light emitting device with improved light emission characteristics can be obtained.

<Preferred form>
In the infrared light emitting device of the first aspect, it is preferable that the substrate is a GaAs substrate, and further includes a buffer layer formed of a compound semiconductor layer containing InAs, AlGaSb, or GaSb and formed between the substrate and the n-type contact layer. .

  The infrared light emitting device of the first aspect preferably further includes a p-type contact layer formed of a compound semiconductor layer containing InAsSb, GaSb, or GaInSb having the same composition as the active layer and formed on the second barrier layer.

[Second embodiment]
<Configuration>
As shown in FIG. 2, the infrared light emitting device of the second aspect includes a substrate 1, a p-type contact layer 6 formed on one surface (on the substrate) of the substrate 1, and a substrate of the p-type contact layer 6. The second barrier layer 5 formed on the opposite surface (on the p-type contact layer) and the surface opposite to the p-type contact layer 6 of the second barrier layer 5 (on the second barrier layer) The active layer 4 and the 1st barrier layer 3 which has the n-type conductivity type formed in the surface (on an active layer) on the opposite side to the 2nd barrier layer 5 of the active layer 4 are provided. The first barrier layer 3 having n-type conductivity includes a compound semiconductor layer containing Al, In, As, and Sb. The active layer 4 includes a compound semiconductor layer containing InAs _x Sb _(1-x) (0 ≦ x ≦ 1). The second barrier layer 5 includes a compound semiconductor layer containing Al, Ga, As, and Sb.

<Action, effect>
According to the infrared light emitting device of the second aspect, the second barrier layer including the compound semiconductor layer including Al, Ga, As, and Sb, and the n-type conductivity type including the compound semiconductor layer including Al, In, As, and Sb. A first barrier layer having a band offset (ΔEc) of a conductor between the active layer and the second barrier layer, and a valence band between the active layer and the first barrier layer having the n-type conductivity type. The band offset (ΔEv) can be made sufficiently large.

  Thereby, the infrared light emitting element of the 2nd aspect has improved the barrier function by the 1st barrier layer and the 2nd barrier layer. That is, according to the second aspect of the present invention, an infrared light emitting device with improved light emission characteristics can be obtained.

<Preferred form>
In the infrared light emitting device of the second aspect, the substrate is preferably a GaAs substrate, and the p-type contact layer preferably includes a compound semiconductor layer containing GaSb.

  The infrared light emitting device of the second aspect preferably further includes an n-type contact layer formed on the first barrier layer made of a compound semiconductor layer containing InAsSb and having an n-type conductivity type.

[Common to the first and second embodiments]
<Background to knowledge>
In order to realize an infrared light emitting element having good characteristics, the barrier layer plays an important role. The barrier layer is a layer formed in contact with the active layer and has a function of preventing diffusion current. The second barrier layer preferably has a sufficiently large band offset (ΔEc) in the conduction band with the active layer. The first barrier layer having n-type conductivity preferably has a sufficiently large band offset (ΔEv) in the valence band with the active layer. Since electrons have a longer diffusion length than holes, it is preferable that the barrier layer is sufficiently thick, particularly in the second barrier layer.

  It is conceivable to select a material having a larger band gap than the active layer as the material of the barrier layer, but the mixed crystal composition is obtained by adding a certain amount of Al or Ga to the material of the active layer as the material of the barrier layer. In many cases, the band gap, the conduction band offset (ΔEc), and the valence band offset (ΔEv) are greatly increased by increasing.

  However, the lattice mismatch with the active layer tends to increase as the mixed crystal composition of Al or Ga in the barrier layer increases. As a result, the critical film thickness of the barrier layer becomes small, which causes a problem that a barrier layer having a sufficient film thickness cannot be formed. That is, particularly in the second barrier layer, it is important to select a material having a lattice constant close to that of the active layer and a large band offset (ΔEc) of the conduction band.

On the other hand, in the infrared light emitting device of the first aspect and the second aspect, the material including at least Al, Ga, As, and Sb is the material of the second barrier layer, so that the band offset of the conduction band with the active layer (ΔEc) can be increased. Further, since the material containing at least Al, Ga, As, and Sb has a lattice constant close to that of InAs _x Sb _(1-x) (0 ≦ x ≦ 1) that is the material of the active layer, the film of the second barrier layer The thickness can be increased. The second barrier layer is often p-type doped to further increase the band offset (ΔEc) of the conduction band. However, the material including at least Al, Ga, As, and Sb can increase the band offset (ΔEc) of the conduction band with respect to InAs _x Sb _(1-x) (0 ≦ x ≦ 1) that is the active layer, The band offset (ΔEv) of the valence band is very small. When the second barrier layer is p-type doped, the band offset (ΔEv) of the valence band becomes too small, and there is a risk of causing a leakage current due to the band offset. In order to keep the band offset (ΔEv) of the valence band above a certain amount, the second barrier layer may be non-doped or n-type doped. Alternatively, a material containing at least Al, Ga, In, As, and Sb to which a certain amount of In is added may be used as the material of the second barrier layer. Further, by using a material containing at least Al, In, As, and Sb as the material of the first barrier layer having the n-type conductivity type, it is possible to increase the band offset (ΔEv) of the valence band with the active layer. It becomes. As a result, the function of preventing the diffusion current can be enhanced and the characteristics of the infrared light emitting element can be improved.

<Production method>
The infrared light emitting device of the first embodiment and the second embodiment is manufactured through a process of forming each layer on a substrate. This step can be performed by, for example, a molecular beam epitaxy (MBE) method or a metal organic vapor phase epitaxy (MOVPE) method.

<Additional configuration>
The infrared light emitting device of the first aspect and the second aspect can further include an electrode formed on the n-type contact layer and the p-type contact layer, and a passivation film.

  A plurality of infrared light emitting elements of the first and second embodiments may be formed on a substrate and electrically connected in series. With such a structure, it becomes possible to add the outputs of a single infrared light emitting element, and the output can be dramatically improved.

  In addition, the infrared light emitting element of the first aspect or the second aspect and the integrated circuit unit that processes an electric signal output from the infrared light emitting element may be formed in a hybrid in the same package. An electrical connection method between the infrared light emitting element and the integrated circuit portion is not particularly limited. The package is not particularly limited as long as it has a high infrared transmittance, and a hollow package or the like may be used.

<Details about each configuration>
(substrate)
The substrate is not particularly limited as long as a compound semiconductor layer can be grown thereon, and a single crystal substrate such as a GaAs substrate or a Si substrate is preferable. Further, these single crystal substrates may be doped n-type or p-type with donor impurities or acceptor impurities.

  The plane orientation of the single crystal substrate is not particularly limited, but (100), (111), (110) and the like are preferable. Further, a plane orientation inclined by 1 ° to 5 ° with respect to these plane orientations can be used.

  When a plurality of infrared light emitting elements formed on the surface of the substrate are used connected in series with electrodes, it is preferable that each infrared light emitting element is insulated and separated at portions other than the electrodes. Therefore, as the substrate, it is preferable to use a semi-insulating substrate or a substrate capable of insulating and separating the stacked body of each layer formed on the substrate and the substrate.

  Further, by using a material that transmits infrared rays as the substrate, infrared rays can be extracted from the back side of the substrate. In this case, the infrared light is not blocked by the electrode, which is preferable in that the light receiving area of the element can be increased. As a material for such a substrate, semi-insulating Si or GaAs is preferable.

  As is usually done, a substrate in which a semiconductor layer made of the same material as that of the substrate is formed for the purpose of flattening and cleaning the surface of the substrate can be used as the substrate. The most representative example of this is that a GaAs layer formed on a GaAs substrate is used as the substrate.

(Buffer layer)
The infrared light emitting device of the first aspect preferably further includes a buffer layer between the substrate and the n-type contact layer. The buffer layer is formed on the surface of the substrate. The buffer layer functions as a layer for improving all crystallinity formed thereon. Thereby, an active layer with good crystallinity (with few defects) can be obtained.

  In the infrared light emitting device of the second aspect, a buffer layer may be further provided between the substrate and the p-type contact layer.

  Examples of the material for the buffer layer include InSb, InAs, InAsSb, AlInSb, GaInSb, AlGaInSb, AlInAsSb, GaInAsSb, AlGaInAsSb, AlSb, GaSb, AlGaSb, AlAsSb, GaAsSb, and AlGaAsSb. The buffer layer may be a single layer made of one of these materials or a multilayer in which a plurality of layers are stacked. In addition, a graded buffer layer formed so that the lattice constant is brought close to the composition of the layer (n-type contact layer or p-type contact layer) formed thereon while changing the composition of the material continuously or stepwise. May be used.

  The material of the buffer layer can be confirmed by a secondary ion mass spectrometry (SIMS) method. The material of other layers can be confirmed by the same method.

  InAs single-layer film, GaSb single-layer film, and AlGaSb single-layer film can be (a) easy to form a film with good crystallinity, and (b) lattice mismatch with an active layer containing InAsSb can be close to zero. (C) A single-layer film is preferable as a material for the buffer layer from the viewpoint that a film thickness is thinner than a graded layer and the like, and the formation time is short.

When the buffer layer is an AlGaSb single layer film, the electrical resistance increases as the Al composition ratio y of Al _y Ga _(1-y) Sb (0 ≦ y ≦ 1) increases. However, crystallinity tends to deteriorate. Therefore, the Al composition ratio y is appropriately selected according to the desired resistance and crystallinity. If the Al composition ratio y of Al _y Ga _(1-y) Sb (0 ≦ y ≦ 1) is too large, oxidation corrosion tends to occur. Therefore, from the viewpoint of easy oxidation and corrosion, the Al composition ratio y is set to 0. It is preferable that it is 0.8 or more.

  Moreover, since the GaSb single layer film can be formed into a film having better crystallinity than the AlGaSb single layer film, it is more preferable to use the GaSb single layer film from the viewpoint of obtaining good crystallinity.

  If the buffer layer is too thin, the effect of improving the crystallinity of the active layer is lost. If it is too thick, it takes time to form and the mesa etching process for element isolation becomes difficult. Is preferred.

  The thickness of the buffer layer can be measured by a cross-sectional TEM (TEM: Transmission Electron Spectroscopy) method. Specifically, sample preparation can be performed by the FIB method using a Hitachi FIB apparatus (FB-2100), and the thickness can be measured by cross-sectional observation using a Hitachi STEM apparatus (HD-2300A). The film thicknesses of layers other than the buffer layer can also be measured by using the same measurement method.

  When using a GaSb single layer film and an AlGaSb single layer film as a buffer layer, the buffer layer may be non-doped, or may be doped n-type or p-type.

  When an n-type contact layer is formed on the buffer layer, the n-type contact layer may be formed on a single layer film of non-doped GaSb or AlGaSb. Also, a single layer film of GaSb or AlGaSb doped in n-type may be used as an n-type contact layer as it is.

  On the other hand, when a p-type contact layer is formed on the buffer layer, a p-type doped GaSb or AlGaSb single layer film may be used as a p-type contact layer as it is. Regarding the p-type conversion of GaSb and AlGaSb single-layer films, it is preferable because the vapor pressure is low and Si, which is the most commonly used group IV element, can be used as a dopant.

(N-type contact layer)
The n-type contact layer functions as a contact layer with the electrode. Examples of the material of the n-type contact layer include InSb, InAs, InAsSb, AlInSb, GaInSb, AlGaInSb, AlInAsSb, GaInAsSb, AlGaInAsSb, AlSb, GaSb, AlGaSb, AlAsSb, GaAsSb, and AlGaAsSb.

The sheet resistance of the n-type contact layer causes Johnson noise that is thermal noise. Therefore, the sheet resistance should be as small as possible. The n-type contact layer needs to be sufficiently doped to reduce contact resistance. Therefore, the doping concentration is preferably 1 × 10 ¹⁸ / cm ³ or more. Examples of the n-type dopant include Si, Sn, S, Se, Te, and Ge.

  As a material of the n-type contact layer, (d) InAsSb forming an active layer is close to a lattice constant, (e) a vapor pressure is low, and Si, which is the most commonly used group IV element, can be used as a dopant. (F) InAs or InAsSb is particularly preferable from the viewpoint that sheet resistance can be reduced. The use of InAsSb, which is the same material as the active layer, is more preferable because the lattice constant can be made to coincide completely.

  The thickness of the n-type contact layer is preferably as thick as possible in order to reduce the sheet resistance. However, if it is too thick, it takes time to form and a mesa etching process for element isolation becomes difficult. For this reason, as a film thickness of an n-type contact layer, 0.1 to 1 micrometer is mentioned as a preferable range.

(First barrier layer having n-type conductivity)
1st aspect and 2nd aspect The 1st barrier layer which has the n-type conductivity type of infrared light emitting element consists of a compound semiconductor layer containing Al, In, As, and Sb, and has a function which prevents the diffusion current from an active layer. By using a material containing Al, In, As, and Sb having a large band gap as a first barrier layer with respect to the active layer containing InAs _x Sb _(1-x) (0 ≦ x ≦ 1), The band offset (ΔEv) increases.

  When the lattice constants of the active layer and the first barrier layer are different, the crystallinity of the first barrier layer deteriorates when the film thickness of the first barrier layer exceeds the critical film thickness. Alternatively, it is necessary to consider both the band offset of the valence band and the deterioration of crystallinity. From the viewpoint of increasing the thickness of the first barrier layer, the difference in lattice constant between the active layer and the first barrier layer is preferably as small as possible.

Also, the first barrier layer can lower the upper end of the valence band by n-type doping, and functions more effectively as a diffusion barrier for thermally excited holes. Therefore, the first barrier layer needs to be sufficiently doped. The doping concentration is preferably 1 × 10 ¹⁸ / cm ³ or more. Examples of the n-type dopant include Si, Sn, S, Se, Te, and Ge.

  When the material of the first barrier layer is AlInAsSb, if the Al composition ratio of AlInAsSb is too small, a sufficient band offset of the valence band cannot be secured, and if the Al composition ratio of AlInAsSb is too large, the active layer containing InAsSb And the critical thickness of the first barrier layer becomes small, so that a sufficient thickness as the n-type barrier layer cannot be secured. Therefore, the Al composition ratio of AlInAsSb is preferably 0.1 or more and 0.5 or less.

  The film thickness of the first barrier layer is preferably as thin as possible in order to reduce the resistance of the infrared light emitting element. However, a film thickness that does not cause a tunnel leak between the electrode and the active layer is required. For this reason, the film thickness of the first barrier layer is preferably 0.01 μm or more, more preferably 0.02 μm or more. The upper limit of the film thickness of the first barrier layer is limited by the critical film thickness determined by the difference between the lattice constants of the active layer and the first barrier layer.

(Active layer)
The active layer of the infrared light emitting device of the first embodiment and the second embodiment includes InAs _x Sb _(1-x) (0 ≦ x ≦ 1). The As composition ratio x of the active layer is not particularly limited, but by setting the As composition ratio x to a desired value, the peak wavelength of infrared light emission can be controlled over a wide range of 3 μm to 10 μm. When InAs, AlGaSb, or GaSb is used as the buffer layer, a better crystal can be obtained when the lattice constant of InAsSb in the active layer is closer to the lattice constant of the buffer layer. Therefore, the As composition ratio x is 0.7 or more and 1 The following is preferred.

  The thickness of the active layer is preferably thick in order to increase the amount of light absorption, but if it is too thick, it takes time to form and the mesa etching process for element isolation becomes difficult, so 0.5 μm or more and 3 μm or less Is preferred.

  The active layer may be non-doped or may be doped n-type or p-type. Since InAsSb has a very small band gap, the intrinsic carrier density is very large. This results in increased diffusion current and promotion of the Auger recombination process. These effects can be reduced by doping the active layer p-type. The doping amount is set as appropriate.

In general, Be, Zn, Cd, C, Mg, Ge, or the like is preferably used as the p-type dopant of the active layer containing InAs _x Sb _(1-x) (0 ≦ x ≦ 1). Since activation rate is high and toxicity is low, it is more preferably used.

(Second barrier layer)
The 2nd barrier layer of the infrared light emitting element of the 1st aspect and the 2nd aspect consists of a compound semiconductor layer containing Al, Ga, As, and Sb, and has a function which prevents the diffused current from an active layer. By using a material containing Al, Ga, As and Sb having a large band gap as a material of the second barrier layer with respect to the active layer containing InAs _x Sb _(1-x) (0 ≦ x ≦ 1), the conduction band Band offset (ΔEc) increases.

In addition, the second barrier layer can raise the lower end of the conduction band by p-type doping and functions more effectively as a diffusion barrier for thermally excited electrons. For this reason, the second barrier layer is often p-type doped with a doping concentration of 1 × 10 ¹⁸ / cm ³ or more. However, the material including at least Al, Ga, As, and Sb can increase the band offset (ΔEc) of the conduction band with respect to InAs _x Sb _(1-x) (0 ≦ x ≦ 1) that is the active layer, The band offset (ΔEv) of the valence band is very small. When the second barrier layer is p-type doped, the band offset (ΔEv) of the valence band becomes too small, and there is a risk of causing a leakage current due to the band offset. In order to keep the band offset (ΔEv) of the valence band above a certain amount, the second barrier layer may be non-doped or n-type doped. Alternatively, a material containing at least Al, Ga, In, As, and Sb to which a certain amount of In is added may be used as the material of the second barrier layer.

Since the difference in lattice constant from InAs _x Sb _(1-x) (0 ≦ x ≦ 1) contained in the active layer is sufficiently small, the Al composition ratio of the second barrier layer is not limited by the critical film thickness. However, if the Al composition ratio is too large, there is a concern of oxidation, corrosion, and the like. Therefore, the Al composition ratio is preferably 0 or more and 0.8 or less. Further, if the As composition ratio is too small, there is a concern that the band offset (ΔEv) of the valence band with the active layer InAsSb becomes too small. On the other hand, if the As composition is too large, the difference in lattice constant from the active layer InAsSb increases and is restricted by the critical film thickness, so the As composition is preferably 0.01 or more and 0.3 or less.

  The film thickness of the second barrier layer is preferably as thin as possible in order to reduce the element resistance of the light emitting element, but it is necessary to have a film thickness that does not cause a tunnel leak between the electrode and the active layer. For this reason, the film thickness of the second barrier layer is preferably 0.01 μm or more, more preferably 0.02 μm or more. Note that the upper limit of the thickness of the second barrier layer is limited by the critical thickness determined by the difference between the lattice constants of the active layer and the second barrier layer.

(P-type contact layer)
The p-type contact layer functions as a contact layer with the electrode. Examples of the material of the p-type contact layer include InSb, InAs, InAsSb, AlInSb, GaInSb, AlGaInSb, AlInAsSb, GaInAsSb, AlGaInAsSb, AlSb, GaSb, AlGaSb, AlAsSb, GaAsSb, and AlGaAsSb.

The sheet resistance of the p-type contact layer causes Johnson noise that is thermal noise. Therefore, the sheet resistance should be as small as possible. The p-type contact layer needs to be sufficiently doped to reduce the contact resistance. Therefore, the doping concentration is preferably 1 × 10 ¹⁸ / cm ³ or more. Examples of the p-type dopant include Be, Zn, Cd, C, Mg, and Ge.

As the material of the p-type contact layer, (d) the lattice constant is close to InAs _x Sb _(1-x) (0 ≦ x ≦ 1) contained in the active layer, (e) the vapor pressure is low, and most commonly AlGaSb and GaSb are preferable from the viewpoint that Si, which is a group IV element used, can be used as a dopant, and (f) sheet resistance can be reduced. It is preferable that the material of the p-type contact layer is GaSb because sheet resistance can be reduced as compared with the case of AlGaSb.

  In addition, since lattice matching with InAsSb is possible by controlling the In composition, it is also preferable to use GaInSb as the material of the p-type contact layer.

  Of course, InAsSb having the same composition as the active layer may be used as the p-type contact layer. In this case, examples of the p-type dopant include Be, Zn, Cd, C, Mg, and Ge.

  The p-type contact layer is preferably as thick as possible in order to reduce the sheet resistance. However, if it is too thick, it takes time to form and a mesa etching process for element isolation becomes difficult. For this reason, the preferable thickness of the p-type contact layer is 0.1 μm or more and 1 μm or less.

(Passivation film)
The passivation film is not particularly limited as long as it is an insulating film. Examples of the material for the passivation film include a silicon nitride film (Si ₃ N ₄ ), a silicon oxide film (SiO ₂ ), and a silicon oxynitride film (SiON).

(electrode)
The electrodes include a p-type electrode that is electrically connected to the p-type contact layer and an n-type electrode that is electrically connected to the n-type contact layer. The electrode is not particularly limited as long as it is composed of a conductive film, and examples thereof include a laminated film in which the upper layer / lower layer is Au / Ti or Au / Cr.

[Embodiment]
Hereinafter, although embodiment of this invention is described, this invention is not limited to embodiment shown below. In the embodiment described below, a technically preferable limitation is made for carrying out the present invention, but this limitation is not an essential requirement of the present invention.

  Note that in the drawings used in the following description, the dimensional relationships of the respective parts illustrated may be different from the actual dimensional relationships.

<First embodiment>
(Constitution)
As shown in FIG. 3, the infrared light emitting device of the first embodiment includes a substrate 1, a buffer layer 7, an n-type contact layer 2, an n-type conductivity first barrier layer 3, and an active layer 4. The second barrier layer 5, the p-type contact layer 6, the n-type electrode 8, the p-type electrode 9, and the passivation film 10 are provided.

  A buffer layer 7, an n-type contact layer 2, a first barrier layer 3 having an n-type conductivity, an active layer 4, a second barrier layer 5, and a p-type contact layer 6 are formed in this order on the substrate 1. Yes. That is, the compound semiconductor stack including the buffer layer 7, the n-type contact layer 2, the first barrier layer 3 having the n-type conductivity, the active layer 4, the second barrier layer 5, and the p-type contact layer 6 is formed on the substrate 1. Formed on top.

  The widths of the buffer layer 7 and the n-type contact layer 2 are larger than the widths of the first barrier layer 3, the active layer 4, the second barrier layer 5, and the p-type contact layer 6 having n-type conductivity. That is, there is a step between the n-type contact layer 2 and the first barrier layer 3 having n-type conductivity. An n-type electrode 8 is formed on the upper surface of the n-type contact layer 2 generated by this step, and a p-type electrode 9 is formed on the upper surface of the p-type contact layer 6.

  The passivation film 10 covers the upper surface of the substrate 1, the side surfaces and the upper surface of the compound semiconductor stacked body. Upper portions of the n-type electrode 8 and the p-type electrode 9 are exposed from the passivation film 10.

The substrate 1 contains GaAs. The buffer layer 7 contains InAs, AlGaSb, or GaSb. The n-type contact layer 2 contains InAsSb containing Si (n-type dopant). The first barrier layer 3 having n-type conductivity includes AlInAsSb containing Si (n-type dopant). The active layer 4 includes InAs _x Sb _(1-x) (0 ≦ x ≦ 1). The second barrier layer 5 includes AlGaAsSb. The p-type contact layer 6 contains GaSb or GaInSb containing Si (p-type dopant) or InAsSb containing Zn (p-type dopant). The n-type electrode 8 contains Au / Ti. The p-type electrode 9 contains Au / Ti. The passivation film 10 includes silicon nitride.

(Function, effect)
According to the infrared light emitting device of the first embodiment, by providing the second barrier layer 5 containing AlGaAsSb, the band offset (ΔEc) of the conductor between the active layer 4 and the second barrier layer 5 can be sufficiently increased. it can. Moreover, by having the buffer layer 7 containing InAs, AlGaSb, or GaSb, the crystallinity of the active layer 4 containing InAs _x Sb _(1-x) (0 ≦ x ≦ 1) is improved. Further, since the n-type contact layer 2 contains the same InAsSb as the active layer 4, the lattice constants of the n-type contact layer 2 and the active layer 4 are the same.

In addition, since the first barrier layer 3 having the n-type conductivity includes AlInAsSb having a large band gap energy with respect to InAs _x Sb _(1-x) (0 ≦ x ≦ 1) forming the active layer 4, A large band offset (ΔEv) can be obtained. The p-type contact layer 6 includes GaSb, GaInSb, or InAsSb having a lattice constant close to that of InAs _x Sb _(1-x) (0 ≦ x ≦ 1) forming the active layer 4.

  From the above, according to the infrared light emitting device of the first embodiment, good light emission characteristics can be obtained.

(Production method)
First, an MBE (molecular beam epitaxy) method is used on the upper surface of a GaAs wafer (substrate 1) to form a buffer layer 7, an n-type contact layer 2, an n-type conductivity first barrier layer 3, an active layer 4, 2 barrier layer 5 and p-type contact layer 6 are formed. Next, the first barrier layer 3, the active layer 4, the second barrier layer 5, and the p-type contact layer 6 having n-type conductivity are partially formed on each element by wet etching using acid or ion milling. Then, a step for forming a contact between the n-type contact layer 2 and the n-type electrode 8 is formed. As a result, a plurality of compound semiconductor stacks having steps are formed on the GaAs wafer.

  Next, mesa etching for element isolation is performed on the plurality of compound semiconductor stacks having steps. Here, the n-type contact layer and the buffer layer appearing at the bottom of the step are partially removed sequentially. Thereby, the upper surface of the substrate 1 is exposed in the element isolation region.

  Next, a passivation film 10 containing silicon nitride covers the upper surface of the substrate 1 and the upper surface and side surfaces of the compound semiconductor stacked body from which elements have been separated.

  Next, a portion of the passivation film 10 where the n-type electrode 8 and the p-type electrode 9 are formed is etched to form a through hole. Next, an Au / Ti electrode is formed so as to fill the through hole by a lift-off method or the like.

<Second embodiment>
(Constitution)
As shown in FIG. 4, the infrared light emitting device of the second embodiment includes a substrate 1, a p-type contact layer 6, a second barrier layer 5, an active layer 4, and a first barrier layer having an n-type conductivity type. 3, an n-type contact layer 2, an n-type electrode 8, a p-type electrode 9, and a passivation film 10.

  A p-type contact layer 6, a second barrier layer 5, an active layer 4, a first barrier layer 3 having n-type conductivity, and an n-type contact layer 2 are formed on the substrate 1 in this order. . That is, the compound semiconductor stack including the p-type contact layer 6, the second barrier layer 5, the active layer 4, the first barrier layer 3 having n-type conductivity, and the n-type contact layer 2 is formed on the substrate 1. Formed on top.

  The width of the p-type contact layer 6 is larger than the width of the second barrier layer 5, the active layer 4, the first barrier layer 3 having n-type conductivity, and the n-type contact layer 2. That is, there is a step between the p-type contact layer 6 and the second barrier layer 5. A p-type electrode 9 is formed on the upper surface of the p-type contact layer 6 generated by this step, and an n-type electrode 8 is formed on the upper surface of the n-type contact layer 2.

  The passivation film 10 covers the upper surface of the substrate 1, the side surfaces and the upper surface of the compound semiconductor stacked body. Upper portions of the n-type electrode 8 and the p-type electrode 9 are exposed from the passivation film 10.

The substrate 1 contains GaAs. The n-type contact layer 2 contains InAsSb containing Si (n-type dopant). The first barrier layer 3 having n-type conductivity includes AlInAsSb containing Si (n-type dopant). The active layer 4 includes InAs _x Sb _(1-x) (0 ≦ x ≦ 1). The second barrier layer 5 includes AlGaAsSb. The p-type contact layer 6 contains GaSb containing Si (p-type dopant). The n-type electrode 8 contains Au / Ti. The p-type electrode 9 contains Au / Ti. The passivation film 10 includes silicon nitride.

(Function, effect)
According to the infrared light emitting device of the second embodiment, by providing the second barrier layer 5 containing AlGaAsSb, the band offset (ΔEc) of the conductor between the active layer 4 and the second barrier layer 5 can be sufficiently increased. it can.

Further, since the n-type contact layer 2 contains the same InAsSb as the active layer 4, the lattice constants of the n-type contact layer 2 and the active layer 4 are the same. In addition, since the first barrier layer 3 having the n-type conductivity includes AlInAsSb having a large band gap energy with respect to InAs _x Sb _(1-x) (0 ≦ x ≦ 1) forming the active layer 4, A large band offset (ΔEv) can be obtained. The p-type contact layer 6 contains GaSb having a lattice constant close to that of InAs _x Sb _(1-x) (0 ≦ x ≦ 1) forming the active layer 4, so that InAs _x Sb _{(1 -x)} The crystallinity of (0 ≦ x ≦ 1) can be improved.

  From the above, according to the infrared light emitting device of the second embodiment, good light emission characteristics can be obtained.

(Production method)
The infrared light emitting device of the second embodiment differs from the infrared light emitting device of the first embodiment in the configuration of the compound semiconductor laminate, so the formation order of each layer is different, but basically the method described in the first embodiment. Can be manufactured.

  Examples of the present invention will be described below.

[Example 1]
An infrared light emitting device having the structure shown in FIG. 3 was produced as follows.

  By the MBE method, a buffer layer 7, an n-type contact layer 2, a first barrier layer 3 having an n-type conductivity, an active layer 4, and a second layer are formed on a substrate 1 containing a semi-insulating GaAs single crystal. By sequentially laminating the barrier layer 5 and the p-type contact layer 6, a compound semiconductor multilayer body having a PIN structure was formed.

In this stacking step, an n-type InAs layer doped with Si at 7 × 10 ¹⁸ / cm ³ was formed as the buffer layer 7 to a thickness of 0.5 μm. As the n-type contact layer 2, an n-type InAs _0.87 Sb _0.13 layer doped with Si of 7 × 10 ¹⁸ / cm ³ was formed with a thickness of 0.7 μm. As the first barrier layer 3 having n-type conductivity, an n-type Al _0.3 In _0.7 As _0.87 Sb _0.13 layer doped with Si at 7 × 10 ¹⁸ / cm ³ was formed to a thickness of 0.02 μm. As the active layer 4, a non-doped InAs _0.87 Sb _0.13 layer was formed with a thickness of 2 μm. As the second barrier layer 5, a non-doped Al _0.4 Ga _0.6 As _0.15 Sb _0.85 layer was formed with a thickness of 0.02 μm. As the p-type contact layer 6, a p-type InAs _0.87 Sb _0.13 layer doped with Zn at 3 × 10 ¹⁸ / cm ³ was formed to a thickness of 0.5 μm.

With respect to the active layer 4 containing InAs _0.87 Sb _0.13 in the obtained compound semiconductor laminated body, the half width (FWHM value) of the rocking curve of the X-ray diffraction peak was 380 arcsec.

  The infrared light emitting element of Example 1 was produced by performing the following steps on this compound semiconductor laminate.

  First, step formation for making contact with the n-type contact layer 2 was performed by wet etching using an acid or ion milling. Next, mesa etching for element isolation was performed on the compound semiconductor stacked body on which the step was formed. Thereafter, the upper surface of the substrate 1 and the upper surface and side surfaces of the compound semiconductor stacked body from which the elements were separated were covered with a passivation film 10 containing SiN. Next, a through hole was formed in the electrode formation portion of the passivation film 10. Next, Au / Ti is deposited by EB (electron beam) deposition on the step portion of the n-type contact layer 2 and on the p-type contact layer 6, and the n-type electrode 8 and the p-type electrode are formed in each through hole by a lift-off method. 9 was formed respectively.

  In this way, an infrared light emitting device having the structure shown in FIG. 3 was obtained.

[Example 2]
In the lamination process of the PIN structure, a non-doped Al _0.55 Ga _0.45 Sb layer was formed as the buffer layer 7 with a thickness of 0.5 μm. As the n-type contact layer 2, an n-type InAs _0.87 Sb _0.13 layer doped with Si of 7 × 10 ¹⁸ / cm ³ was formed with a thickness of 0.7 μm. As the first barrier layer 3 having n-type conductivity, an n-type Al _0.3 In _0.7 As _0.87 Sb _0.13 layer doped with Si at 7 × 10 ¹⁸ / cm ³ was formed to a thickness of 0.02 μm. As the active layer 4, a non-doped InAs _0.87 Sb _0.13 layer was formed with a thickness of 2 μm. As the second barrier layer 5, a non-doped Al _0.4 Ga _0.6 As _0.15 Sb _0.85 layer was formed with a thickness of 0.02 μm. As the p-type contact layer 6, a p-type InAs _0.87 Sb _0.13 layer doped with Zn at 3 × 10 ¹⁸ / cm ³ was formed to a thickness of 0.5 μm.

With respect to the active layer 4 containing InAs _0.87 Sb _0.13 in the obtained compound semiconductor laminated body, the half width (FWHM value) of the rocking curve of the X-ray diffraction peak was 306 arcsec.

  By performing the same process as Example 1 with respect to this compound semiconductor laminated body, the infrared light emitting element of Example 2 was produced.

[Example 3]
In the lamination process of the PIN structure, a non-doped GaSb layer was formed as the buffer layer 7 with a thickness of 0.5 μm. As the n-type contact layer 2, an n-type InAs _0.87 Sb _0.13 layer doped with Si of 7 × 10 ¹⁸ / cm ³ was formed with a thickness of 0.7 μm. As the first barrier layer 3 having n-type conductivity, an n-type Al _0.3 In _0.7 As _0.87 Sb _0.13 layer doped with Si at 7 × 10 ¹⁸ / cm ³ was formed to a thickness of 0.02 μm. As the active layer 4, a non-doped InAs _0.87 Sb _0.13 layer was formed with a thickness of 2 μm. As the second barrier layer 5, a non-doped Al _0.4 Ga _0.6 As _0.15 Sb _0.85 layer was formed with a thickness of 0.02 μm. As the p-type contact layer 6, a p-type InAs _0.87 Sb _0.13 layer doped with Zn at 3 × 10 ¹⁸ / cm ³ was formed to a thickness of 0.5 μm.

With respect to the active layer 4 containing InAs _0.87 Sb _0.13 in the obtained compound semiconductor laminated body, the half width (FWHM value) of the rocking curve of the X-ray diffraction peak was 185 arcsec.

  By performing the same process as Example 1 with respect to this compound semiconductor laminated body, the infrared light emitting element of Example 3 was produced.

[Example 4]
In the lamination process of the PIN structure, a non-doped GaSb layer was formed as the buffer layer 7 with a thickness of 0.5 μm. As the n-type contact layer 2, an n-type InAs _0.87 Sb _0.13 layer doped with Si of 7 × 10 ¹⁸ / cm ³ was formed with a thickness of 0.7 μm. As the first barrier layer 3 having n-type conductivity, an n-type Al _0.3 In _0.7 As _0.87 Sb _0.13 layer doped with Si at 7 × 10 ¹⁸ / cm ³ was formed to a thickness of 0.02 μm. As the active layer 4, a non-doped InAs _0.87 Sb _0.13 layer was formed with a thickness of 2 μm. As the second barrier layer 5, a non-doped Al _0.4 Ga _0.6 As _0.15 Sb _0.85 layer was formed with a thickness of 0.02 μm. As the p-type contact layer 6, a p-type GaSb layer doped with Si at 3 × 10 ¹⁸ / cm ³ was formed to a thickness of 0.5 μm.

With respect to the active layer 4 containing InAs _0.87 Sb _0.13 in the obtained compound semiconductor laminated body, the half width (FWHM value) of the rocking curve of the X-ray diffraction peak was 185 arcsec.

  By performing the same process as Example 1 with respect to this compound semiconductor laminated body, the infrared light emitting element of Example 4 was produced.

[Example 5]
In the lamination process of the PIN structure, a non-doped GaSb layer was formed as the buffer layer 7 with a thickness of 0.5 μm. As the n-type contact layer 2, an n-type InAs _0.87 Sb _0.13 layer doped with Si of 7 × 10 ¹⁸ / cm ³ was formed with a thickness of 0.7 μm. As the first barrier layer 3 having n-type conductivity, an n-type Al _0.3 In _0.7 As _0.87 Sb _0.13 layer doped with Si at 7 × 10 ¹⁸ / cm ³ was formed to a thickness of 0.02 μm. As the active layer 4, a non-doped InAs _0.87 Sb _0.13 layer was formed with a thickness of 2 μm. As the second barrier layer 5, a non-doped Al _0.4 Ga _0.6 As _0.15 Sb _0.85 layer was formed with a thickness of 0.02 μm. As the p-type contact layer 6, a p-type Ga _0.96 In _0.04 Sb layer doped with Si at 3 × 10 ¹⁸ / cm ³ was formed to a thickness of 0.5 μm.

With respect to the active layer 4 containing InAs _0.87 Sb _0.13 in the obtained compound semiconductor laminated body, the half width (FWHM value) of the rocking curve of the X-ray diffraction peak was 185 arcsec.

  By performing the same process as Example 1 with respect to this compound semiconductor laminated body, the infrared light emitting element of Example 5 was produced.

[Example 6]
In the lamination process of the PIN structure, a non-doped GaSb layer was formed as the buffer layer 7 with a thickness of 0.5 μm. As the n-type contact layer 2, an n-type InAs _0.87 Sb _0.13 layer doped with Si of 7 × 10 ¹⁸ / cm ³ was formed with a thickness of 0.7 μm. As the first barrier layer 3 having n-type conductivity, an n-type Al _0.3 In _0.7 As _0.87 Sb _0.13 layer doped with Si at 7 × 10 ¹⁸ / cm ³ was formed to a thickness of 0.02 μm. As the active layer 4, a non-doped InAs _0.87 Sb _0.13 layer was formed with a thickness of 2 μm. As the second barrier layer 5, an n-type Al _0.4 Ga _0.6 As _0.15 Sb _0.85 layer doped with Sn at 1 × 10 ¹⁷ / cm ³ was formed to a thickness of 0.02 μm. As the p-type contact layer 6, a p-type InAs _0.87 Sb _0.13 layer doped with Zn at 3 × 10 ¹⁸ / cm ³ was formed to a thickness of 0.5 μm.

With respect to the active layer 4 containing InAs _0.87 Sb _0.13 in the obtained compound semiconductor laminated body, the half width (FWHM value) of the rocking curve of the X-ray diffraction peak was 185 arcsec.

  By performing the same process as Example 1 with respect to this compound semiconductor laminated body, the infrared light emitting element of Example 6 was produced.

  Table 1 summarizes Examples 1 to 6.

[Example 7]
An infrared light emitting device having the structure shown in FIG. 4 was produced as follows.

  By the MBE method, a p-type contact layer 6 also serving as a buffer layer, a second barrier layer 5, an active layer 4, and a first n-type conductivity type are formed on a substrate 1 containing a semi-insulating GaAs single crystal. By sequentially laminating the barrier layer 3 and the n-type contact layer 2, a compound semiconductor multilayer body having a PIN inverse structure was formed.

In this lamination step, a p-type GaSb layer doped with Si at 3 × 10 ¹⁸ / cm ³ was formed to a thickness of 1.0 μm as the p-type contact layer 6 that also served as a buffer layer. Further, as the second barrier layer 5, a non-doped Al _0.4 Ga _0.6 As _0.15 Sb _0.85 layer was formed with a thickness of 0.02 μm. Further, as the active layer 4, a non-doped InAs _0.87 Sb _0.13 layer was formed with a thickness of 2 μm. Further, as the first barrier layer 3 having n-type conductivity, an n-type Al _0.3 In _0.7 As _0.87 Sb _0.13 layer doped with Si at 7 × 10 ¹⁸ / cm ³ was formed with a thickness of 0.02 μm. As the n-type contact layer 2, an n-type InAs _0.87 Sb _0.13 layer doped with Si at 7 × 10 ¹⁸ / cm ³ was formed to a thickness of 0.5 μm.

  In this lamination process, since the vapor pressure is low, the control is simple, and only Si that is generally used without toxicity is used as a dopant. That is, this method is excellent in mass productivity as a method for manufacturing a compound semiconductor stacked body having a PIN inverse structure.

With respect to the active layer 4 containing InAs _0.87 Sb _0.13 in the obtained compound semiconductor stacked body, the half width (FWHM value) of the rocking curve of the X-ray diffraction peak was 184 arcsec.

  The infrared light emitting element of Example 7 was produced by performing the following steps on this compound semiconductor laminate.

  First, step formation for making contact with the p-type contact layer 6 was performed by wet etching using an acid or ion milling. Next, mesa etching for element isolation was performed on the compound semiconductor stacked body on which the step was formed. Thereafter, the upper surface of the substrate 1 and the upper surface and side surfaces of the compound semiconductor stacked body from which the elements were separated were covered with a passivation film 10 containing SiN. Next, a through hole was formed in the electrode formation portion of the passivation film 10. Next, Au / Ti is deposited by EB (electron beam) deposition on the step portion of the p-type contact layer 6 and on the n-type contact layer 2, and the p-type electrode 9 and the n-type electrode are placed in each through hole by a lift-off method. 8 were formed respectively.

  In this way, an infrared light emitting device having the structure shown in FIG. 4 was obtained.

[Example 8]
In the stacking process of the reverse PIN structure described above, a p-type GaSb layer doped with Si at 3 × 10 ¹⁸ / cm ³ was formed to a thickness of 1.0 μm as the p-type contact layer 6 also serving as a buffer layer. Further, as the second barrier layer 5, an n-type Al _0.4 Ga _0.6 As _0.15 Sb _0.85 layer doped with Sn at 1 × 10 ¹⁷ / cm ³ was formed with a thickness of 0.02 μm. Further, as the active layer 4, a non-doped InAs _0.87 Sb _0.13 layer was formed with a thickness of 2 μm. Further, as the first barrier layer 3 having n-type conductivity, an n-type Al _0.3 In _0.7 As _0.87 Sb _0.13 layer doped with Si at 7 × 10 ¹⁸ / cm ³ was formed with a thickness of 0.02 μm. As the n-type contact layer 2, an n-type InAs _0.87 Sb _0.13 layer doped with Si at 7 × 10 ¹⁸ / cm ³ was formed to a thickness of 0.5 μm.

With respect to the active layer 4 containing InAs _0.87 Sb _0.13 in the obtained compound semiconductor stacked body, the half width (FWHM value) of the rocking curve of the X-ray diffraction peak was 184 arcsec.

  By performing the same process as Example 7 with respect to this compound semiconductor laminated body, the infrared light emitting element of Example 8 was produced.

  Table 2 summarizes Example 7 and Example 8.

DESCRIPTION OF SYMBOLS 1 Substrate 2 n-type contact layer 3 First barrier layer 4 having n-type conductivity type Active layer 5 Second barrier layer 6 p-type contact layer 7 Buffer layer 8 n-type electrode 9 p-type electrode 10 Passivation film

Claims (5)

A substrate,
An n-type contact layer formed on the substrate and containing at least In, As and Sb;
A first barrier layer formed on the n-type contact layer and including at least Al, In, As, and Sb and having an n-type conductivity type;
An active layer formed on the first barrier layer and containing InAs _x Sb _(1-x) (0 ≦ x ≦ 1);
A second barrier layer formed on the active layer and including at least Al, Ga, As, and Sb;
An infrared light emitting device comprising: The substrate is a GaAs substrate;
The infrared light emitting element according to claim 1, further comprising a buffer layer containing at least Ga and Sb between the GaAs substrate and the n-type contact layer. A substrate,
A p-type contact layer formed on the substrate;
A second barrier layer formed on the p-type contact layer and including at least Al, Ga, As, and Sb;
An active layer formed on the second barrier layer and containing InAs _x Sb _(1-x) (0 ≦ x ≦ 1);
A first barrier layer formed on the active layer and including at least Al, In, As, and Sb and having an n-type conductivity;
An n-type contact layer formed on the first barrier layer and including at least In, As and Sb;
An infrared light emitting device comprising: The substrate is a GaAs substrate;
The infrared light emitting element according to claim 3, wherein the p-type contact layer includes at least Ga and Sb.   The infrared light emitting element according to any one of claims 1 to 4, wherein the second barrier layer includes an n-type dopant or is non-doped.

Images