Optoelectronic semiconductor device comprising a blocking layer

Abstract

An optoelectronic semiconductor device (10) comprises a semiconductor substrate(100), a first semiconductor layer (110) of a first conductivity type over the semiconductor substrate (100), a first blocking layer (125) having a composition of AlxGayInzP, with 0≤x≤1, 0≤y≤1, 0.45≤z≤0.6, x+y+z=1 and an active region (115) for generating electromagnetic radiation. The active region (115) is arranged over the first semiconductor layer (110) and over the first blocking layer (125). The optoelectronic semiconductor device (10) further comprises a second semiconductor layer (120) of a second conductivity type over the active region (115). The second semiconductor layer (120) has a composition of Alx1Ga1-x1As, with x1> 0.4 or Alx2Ga1- x2-z2Inz2P with 0.45≤z2≤0.6.

Description

[0001] OPTOELECTRONIC SEMICONDUCTOR DEVICE COMPRISING A BLOCKING

[0002] LAYER

[0003] Light-emitting diodes (LEDs) emitting in the IR wavelength range are increasingly being used in health-care monitoring and other systems. Attempts are being made to reduce optical noise in such LEDs .

[0004] It is an object of the present invention to provide an improved optoelectronic semiconductor device.

[0005] SUMMARY

[0006] According to embodiments, the above object is achieved by the claimed matter according to the independent claims. Further developments are defined in the dependent claims.

[0007] According to embodiments, an optoelectronic semiconductor device comprises a semiconductor substrate, a first semiconductor layer of a first conductivity type over the semiconductor substrate, a first blocking layer having a composition of AlxGayInzP, with 0<x<l, 0<y<l, 0.45<z<0.6, x+y+z=l, and an active region for generating electromagnetic radiation. The active region is arranged over the first semiconductor layer and over the first blocking layer. The optoelectronic semiconductor device further comprises a second semiconductor layer of a second conductivity type over the active region. The second semiconductor layer has a composition of AlxlGai-xiAs , with xl> 0.24 or Alx2Gai-X2-Z2lnZ2P with 0.45<z2<0.6.

[0008] For example, x may be less than 0.06.

[0009] According to further embodiments, z may be less than 0.6. For example , a distance hl from a bottom of the first blocking layer to the bottom o f the active region may be larger than 80 nm . Further, a distance h2 from the top of the first blocking layer to a bottom of the active region may be less than 800 nm .

[0010] According to embodiments , a thickness of the first blocking layer may be less than 200 nm .

[0011] The optoelectronic semiconductor device may further comprise a sacri ficial layer between the semiconductor substrate and the first semiconductor layer .

[0012] According to embodiments , the first semiconductor layer may have a composition of AlxGai-xAs with 0<x<l .

[0013] According to embodiments , the optoelectronic semiconductor device may further comprise a second blocking layer between the semiconductor substrate and the first semiconductor layer .

[0014] For example , the second blocking layer may have a composition of Alx2Gai-X2-z2lnZ2P with 0 . 45<z2<0 . 6 , or AlxInyGai-x-yAs , with 0 . 05<y<0 . 2 .

[0015] According to embodiments , an electronic device comprises the optoelectronic semiconductor device as described above .

[0016] The electronic device may be selected from a smart watch, a surveillance camera, a driver monitor and a remote control device .

[0017] BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings are included to provide a further understanding of embodiments of the invention and are incorporated in and constitute a part of this specification. The drawings illustrate the embodiments of the present invention and together with the description serve to explain the principles. Other embodiments of the invention and many of the intended advantages will be readily appreciated, as they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale relative to each other. Like reference numbers designate corresponding similar parts.

[0018] Fig. 1A is a cross-sectional view of an optoelectronic semiconductor device according to embodiments.

[0019] Fig. IB is a cross-sectional view of an optoelectronic semiconductor device according to further embodiments.

[0020] Fig. 2 is a schematic view of an electronic device according to embodiments .

[0021] DETAILED DESCRIPTION

[0022] In the following detailed description reference is made to the accompanying drawings, which form a part hereof and in which are illustrated by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology such as "top", "bottom", "front", "back", "over", "on", "above", "leading", "trailing" etc. is used with reference to the orientation of the Figures being described. Since components of embodiments of the invention can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope defined by the claims.

[0023] The description of the embodiments is not limiting. In particular, elements of the embodiments described hereinafter may be combined with elements of different embodiments.

[0024] The terms "wafer" or "semiconductor substrate" used in the following description may include any semiconductor-based structure that has a semiconductor surface. Wafer and structure are to be understood to include doped and undoped semiconductors, epitaxial semiconductor layers, e.g. supported by a base semiconductor foundation, and other semiconductor structures. For example, a layer of a first semiconductor material may be grown on a growth substrate of a second semiconductor material, e.g. a GaAs substrate, a GaN substrate or a Si substrate. According to further embodiments, the growth substrate may be an insulating substrate such as a sapphire substrate. Depending on the purpose of use, the semiconductor may be based on a direct or an indirect semiconductor material. Examples of semiconductor materials particularly suitable for generation of electromagnetic radiation comprise nitride-compound semiconductors, by which e.g. ultraviolet or blue light or longer wavelength light may be generated, such as GaN, InGaN, AIN, AlGaN, AlGalnN, phosphide-compound semiconductors, by which e.g. green or longer wavelength light may be generated such as GaAsP, AlGalnP, GaP, AlGaP, as well as further semiconductor materials including AlGaAs, InGaAs, InAlGaAs, SiC, ZnSe, GaAs, ZnO, Ga2Os, diamond, hexagonal BN und combinations of these materials. Further examples of semiconductor materials may as well be silicon, silicon-germanium and germanium. The stoichiometric ratio of the compound semiconductor materials may vary. In the context of the present specification, the term "semiconductor" further encompasses organic semiconductor materials. The term "substrate" generally refers to semiconductor substrates, conductive or insulating substrates.

[0025] The terms "lateral" and "horizontal" as used in this specification intends to describe an orientation parallel to a first surface of a substrate or semiconductor body. This can be for instance the surface of a wafer or a die.

[0026] The term "vertical" as used in this specification intends to describe an orientation which is arranged perpendicular to the first surface of a substrate or semiconductor body.

[0027] Fig. 1A shows a vertical cross-sectional view of a portion of an optoelectronic semiconductor device 10 according to embodiments. As is shown, the optoelectronic semiconductor device 10 comprises a semiconductor substrate 100, a first semiconductor layer 110 of a first conductivity type, e.g. p type, over the semiconductor substrate 100, an active region 115 and a second semiconductor layer 120 of a second conductivity type, e.g. n- type. The optoelectronic semiconductor device further comprises a first blocking layer 125 of AlxGayInzP, with 0<x<l, 0<y<l, 0.45<z<0.6 and x+y+z=l. The second semiconductor layer 120 has a composition of AlxlGai-xiAs , with xl>0.24 or Alx2Gai-X2-Z2lnZ2P with 0.45<z2<0.6. Due to the specific composition of the second semiconductor layer and the first blocking layer, an improved charge carrier confinement and less absorption of generated electromagnetic radiation may be achieved.

[0028] The first semiconductor layer 110, the first blocking layer 125, the active region 115 and the second semiconductor layer 120 are arranged to form a semiconductor layer stack. For example, the first blocking layer 125 may be embedded in the first semiconductor layer 110. For example, a portion of the first semiconductor layer 110 may be arranged adj acent to a bottom side 124 and a top side 126 of the first blocking layer 125. The semiconductor layer stack may be formed over a suitable substrate 100 , e . g . a GaAs substrate . For example , the substrate 100 may be a growth substrate .

[0029] For example , when a suitable voltage is applied between the first semiconductor layer 110 and the second semiconductor layer 120 , e . g . by applying a voltage to a terminal electrically connected to the first semiconductor layer 110 and to a second terminal electrically connected to the second semiconductor layer 120 , electromagnetic radiation may be emitted by the optoelectronic semiconductor device 10 . A wavelength of the emitted electromagnetic radiation depends on the material system employed .

[0030] It has been found that due to the presence of the first blocking layer, optical noise of the optoelectronic semiconductor device such as flickering may be reduced . As it has been found out , the optical noise may be generated from a combination of impurity centers and crystal defects near or inside the active region 115 . These impurity centers and crystal defects implement non- radiative charge centers which may frequently and randomly catch or release charge carriers . As a result , a fluctuating electrical field is generated . I f the active region 115 is positioned within this electrical field, the output emission may be strongly influenced by this field . For example , crystal defects may be caused by a small lattice mismatch in the semiconductor layer structure . Due to the presence of the blocking layer 125 , the lattice mismatch may be compensated without the risk that the lattice mismatch extends to the active region 115 .

[0031] According to embodiments , a distance hl from a bottom 124 of the first blocking layer 125 to the bottom 114 of the active region 115 may be larger than 80 nm. As a result, an impact of the defect-rich interface to the active region 115 may be reduced. Moreover, a distance h2 from a top 126 of the first blocking layer 125 to the bottom 114 of the active region 115 may be less than 800 nm or less than 400 nm. As a consequence, a further lattice mismatch may be prevented from being formed in the region between the active region 115 and the first blocking layer 125.

[0032] For example, a thickness of the first blocking layer 125 may be less than 300 nm. Moreover, the thickness of the first blocking layer 125 may be more than 20 nm, e.g. more than 30 nm. For example, an Al content of the first blocking layer 125 may be less than 6 %. Moreover, an In content of the first blocking layer 125 may be less than 60 %, e.g. less than 56 %. Further, an In content may be more than 45 %, e.g. more than 49 %. As a consequence, a lattice of the first blocking layer 125 may be matched to the lattice of the first semiconductor layer 110. For example, the first semiconductor layer 110 may comprise AlxGai-xAs with 0<x<l. For example, the first blocking layer 125 may be tensile strained, neutral or compressively strained. When the thickness of the first blocking layer 125 is less than 200 nm, the first blocking layer 125 may be relaxed during growth. Further, a significant increase of the forward voltage of the LED may be avoided when the thickness is less than 200 nm.

[0033] Due to the reduced noise, the optoelectronic semiconductor device 10 may be used for optical measurements. Further, the brightness of the optoelectronic semiconductor device may be improved .

[0034] The optoelectronic semiconductor device 10 may further comprise a contact layer 130. For example, the contact layer 130 may comprise GaP. The active region 115 for generating electromagnetic radiation may comprise Inx3Aly3Gai-X3-y3Asi-Z3PZ3 with 0<x<l, 0<y<l, 0<z<0.2, x+y<l. For example, the active region 115 employed in the optoelectronic semiconductor device 10 described herein may comprise quantum wells.

[0035] Fig. IB shows a vertical cross-sectional view of an optoelectronic semiconductor device according to further embodiments. In addition to components explained above with reference to Fig. 1A, the optoelectronic semiconductor device may further comprise a second blocking layer 103 which may be arranged between the substrate 100 and the first semiconductor layer 110. The second blocking layer 103 may have a composition of Alx2Gai-x2-z2lnZ2P with 0.45<z2<0.6, or AlxInyGai-x-yAs , with 0.05<y<0.2. Due to the presence of the second blocking layer 103, defects from the substrate 100 may be reduced. For example, the optoelectronic semiconductor device 10 may further comprise a sacrificial layer 105. The sacrificial layer 105 may have a composition of Alx4Gai-X4As , wherein x4>0.5. Due to the presence of the sacrificial layer 105, a lattice mismatch between the substrate 100 and the first semiconductor layer 110 may be reduced .

[0036] Moreover, the optoelectronic semiconductor device may further comprise a bridge layer 127 which is arranged between the contact layer 130 and the second semiconductor layer 120. For example, the bridge layer 127 may comprise doped GaP. A thickness of the bridge layer 127 may be less than 5 nm and more than 0.6 nm. The contact layer 130 may be doped with a second conductivity type. The contact layer may comprise GaP. The bridge layer may reduce a lattice mismatch between the second semiconductor layer 120 and the contact layer 130.

[0037] A confinement layer 117 may be arranged between the first blocking layer 125 and the active region 115. The confinement layer 117 may comprise AlxGai-xAs and may confine carriers to the active region 115 .

[0038] Fig . 2 shows a schematic view of an electronic device 15 according to embodiments . The electronic device 15 comprises the optoelectronic semiconductor device 10 as has been explained above . For example , the electronic device 15 may be a healthcare device , e . g . a device which monitors vital signs such as a sport watch . Since the optoelectronic semiconductor device 10 is particularly suited for emitting light in the IR region, the electronic device 15 may also be a surveillance camera, e . g . a CCTV camera, a driver monitor or a remote control device .

[0039] For example , in high-precise vita-monitoring systems such as sport watches , the oxygen level in the blood vessels is monitored . Due to the fact that optical noise and flickering may be reduced in the described optoelectronic semiconductor device , such a vita-monitoring system may be improved and may be made more reliable .

[0040] As has been described, the optoelectronic semiconductor device 10 comprising the first blocking layer 125 may largely decrease noise such as flickering . The optoelectronic semiconductor device 10 may be implemented in a simple manner .

[0041] While embodiments of the invention have been described above , it is obvious that further embodiments may be implemented . For example , further embodiments may comprise any subcombination of features recited in the claims or any subcombination of elements described in the examples given above . Accordingly, this spirit and scope of the appended claims should not be limited to the description of the embodiments contained herein . LIST OF REFERENCES optoelectronic semiconductor device electronic device semiconductor substrate second blocking layer sacri ficial layer first semiconductor layer bottom of active region active region confinement layer second semiconductor layer bottom of first blocking layer first blocking layer top of first blocking layer bridge layer contact layer

Claims

CLAIMS1. An optoelectronic semiconductor device (10) , comprising : a semiconductor substrate ( 100 ) ; a first semiconductor layer (110) of a first conductivity type over the semiconductor substrate (100) ; a first blocking layer (125) having a composition of AlxGayInzP, with 0<x<l, 0<y<l, 0.45<z<0.6, x+y+z=l, a thickness of the first blocking layer (125) being less than 200 nm, an active region (115) for generating electromagnetic radiation, the active region (115) being arranged over the first semiconductor layer (110) and over the first blocking layer (125) ; a second semiconductor layer (120) of a second conductivity type over the active region (115) , wherein the second semiconductor layer (120) has a composition of AlxlGai-xlAs, with xl> 0.24 or Alx2Gai-X2-Z2lnZ2P with 0.45<z2<0.6.

2. The optoelectronic semiconductor device (10) according to claim 1, wherein x is less than 0.06.

3. The optoelectronic semiconductor device (10) according to claim 1 or 2, wherein z is less than 0.6.

4. The optoelectronic semiconductor device (10) according to any of the preceding claims, wherein a distance hl from a bottom (124) of the first blocking layer (125) to the bottom (114) of the active region (115) is larger than 80 nm.

5. The optoelectronic semiconductor device (10) according to any of the preceding claims, wherein a distance h2 from the top (126) of the first blocking layer (125) to a bottom (114) of the active region (115) is less than 800 nm.

6. The optoelectronic semiconductor device (10) according to any of the preceding claims, wherein a portion of the first semiconductor layer (110) is arranged adjacent to a bottom side (124) and another portion of the first semiconductor layer (110) is arranged adjacent to a top side (126) of the first blocking layer (125) .

7. The optoelectronic semiconductor device (10) according to any of the preceding claims, further comprising a sacrificial layer (105) between the semiconductor substrate (100) and the first semiconductor layer.

8. The optoelectronic semiconductor device (10) according to any of the preceding claims, wherein the first semiconductor layer (110) has a composition of AlxGai-xAs with 0<x<l .

9. The optoelectronic semiconductor device (10) according to any of the preceding claims, further comprising a second blocking layer (103) between the semiconductor substrate (100) and the first semiconductor layer (110) .

10. The optoelectronic semiconductor layer (10) according to claim 9, wherein the second blocking layer (103) has a composition of Alx2Gai-X2-Z2lnZ2P with 0.45<z2<0.6, or AlxInyGai-x-yAs, with 0.05<y<0.2.

11. An electronic device (15) comprising the optoelectronic semiconductor device (10) according to any of claims 1 to 10.

12. The electronic device (15) according to claim 11, which is selected from a smart watch, a surveillance camera, a driver monitor and a remote control device.

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