JP3715639B2 - Semiconductor light emitting device - Google Patents

Description

  The present invention has a ridge buried structure in which a portion removed in a mesa stripe shape of a ridge forming layer is buried with a buried growth layer, or an inner portion in which a part of a current blocking layer removed is buried with a buried growth layer. The present invention relates to a semiconductor light emitting device having a stripe structure.

  When manufacturing a semiconductor laser containing an Al composition such as AlGaAs or InGaAlP, there is a problem of oxidation of the crystal surface during regrowth. In order to solve this problem, a ridge structure, a ridge embedded structure, an internal stripe structure, etc. are mainly employed. Among these, the embedded structure is characterized by easy control of the transverse mode.

FIG. 5 is a cross-sectional view of a semiconductor laser disclosed in Patent Document 1 as an example of a ridge embedded structure. As shown in FIG. 5, a semiconductor laser disclosed in Patent Document 1 below has an n-type AlGaAs cladding layer 22, a GaAs / AlGaAs quantum well active layer + AlGaAs light guide layer 23, p, After the crystal growth of the AlGaAs cladding layer 24 and the p-type GaAs cap layer 25 in order to form an inverted mesa structure, the n-type GaInP current blocking layer 26 and the n-type GaAs layer 27 are grown on the inverted mesa-shaped cut portion. The p-type GaAs cap layer 25, the n-type GaAs layer 27, and the pair of electrodes 28 and 29 are arranged outside the n-type GaAs substrate 21.
JP-A-5-152680

  By the way, in the case of a conventional semiconductor light emitting device having a buried ridge structure, when buried in a GaAs layer, there is a problem that light output characteristics deteriorate due to absorption of light. In order to solve this problem, in the semiconductor laser disclosed in Patent Document 1 shown in FIG. 5, an n-type GaInP current blocking layer 26 is provided between the n-type GaAs layer 27 and the reverse mesa portion of the p-type AlGaAs cladding layer 24. Stable horizontal fundamental transverse mode oscillation was obtained while suppressing light absorption.

  Further, in the case of embedding with only an AlGaAs layer that does not have a light absorption composition, due to the activity of the Al element, it is not normally embedded in the ridge portion, and a non-growth portion (cavity) may occur.

  Further, in the case of a conventional semiconductor light emitting device with a buried ridge structure, the pn junction where the current is blocked is the same as the regrowth interface, and the interface state generated between the ridge surface and the buried layer is interposed. There was a leakage current.

  Therefore, the present invention has been made in view of the above problems, and it is possible to improve the performance of the device by eliminating abnormal growth on the ridge side surface, and to leak current mediated by the interface state at the regrowth interface on the ridge side surface. An object of the present invention is to provide a semiconductor light emitting device capable of improving withstand voltage characteristics by eliminating the above.

In order to achieve the above object, a semiconductor light-emitting device according to claim 1 described in the present invention is configured by using an AlGaAs-based material on a GaAs substrate 1, and a side portion of a ridge forming layer cut into a mesa stripe shape. in the semiconductor light-emitting device the current blocking layer containing Al is arranged as buried growth layer,
A buried buffer layer 7A made of InGaP or InGaAsP is formed directly on the surface of the side of the ridge forming layer cut out in the mesa stripe shape, and the current blocking layer containing Al is formed above the buried buffer layer. It is characterized by being.

According to another aspect of the present invention, a semiconductor light-emitting device is formed of an AlGaAs-based material on a GaAs substrate 1, and a current blocking layer containing Al is formed as a buried growth layer on a side of a ridge forming layer cut out in a mesa stripe shape. In the arranged semiconductor light emitting device,
The buried growth layer includes a plurality of buried buffer layers made of InGaP or InGaAsP between the current blocking layer and the ridge forming layer, and the buried buffer layer is a first buried layer. The conductivity type is the same as that of the clad layer constituting the ridge forming layer, and the conductivity type is inverted when the second buried layer is grown.

According to a third aspect of the present invention , an active layer 3, an etching stop layer 5, and a current block layer 11 are sequentially formed on a GaAs substrate 1, and a part of the current block layer is selectively removed by etching. In a semiconductor light-emitting device made of an AlGaAs-based material, in which a cladding layer 6 containing Al is formed above the portion that has been etched away and the current blocking layer,
A buried buffer layer 7D made of InGaP or InGaAsP is directly formed on the selectively etched portion and the surface of the current blocking layer, and a cladding layer containing the Al is formed above the buried buffer layer. It is characterized by.

  Since an InGaP or InGaAsP layer is provided as a buried buffer layer between the buried layer AlGaAs and the ridge portion, no non-growth portion occurs during buried growth. In addition, there is no light absorption, and the performance of the device is improved.

  The buried structure in which the regrowth interface and the pn junction interface are separated and the pn junction is realized in the same composition so that no interface state is formed. Therefore, the leakage current through the growth interface can be significantly reduced, and the device breakdown voltage and the like can be reduced. The characteristics are improved.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. FIG. 1 is a cross-sectional view showing a first embodiment of a semiconductor light-emitting device according to the present invention, FIG. 2 is a cross-sectional view showing a second embodiment of the semiconductor light-emitting device according to the present invention, and FIG. 3 is a semiconductor according to the present invention. Sectional drawing which shows 3rd Embodiment of a light emitting element, FIG. 4 is sectional drawing which shows 4th Embodiment of the semiconductor light emitting element which concerns on this invention.

  As shown in FIG. 1, the semiconductor light emitting device according to the first embodiment includes a substrate 1, a first cladding layer 2, a quantum well active layer 3, a second cladding layer 4, an etching stop layer 5, a third cladding layer (ridge). Forming layer) 6, buried growth layer 7, fourth cladding layer 8, and contact layer 9 are arranged between a pair of electrodes (not shown) in this order.

  Here, the buried growth layer 7 grows crystals so as to be buried in the side portion 6a of the mesa stripe-shaped ridge formation layer made of the third cladding layer 6 formed on the etching stop layer 5 by the etching process. is there. The buried growth layer 7 has a three-layer structure including a first buried layer 7A, a second buried layer 7B, and a third buried layer 7C from the etching stop layer 5 side. In the example of FIG. 1, the first buried layer 7A is formed of a p-InGaP buried layer (buried buffer layer), and the second buried layer 7B is formed of an n-InGaP buried layer (buried buffer layer). The third buried layer 7C is composed of an n-AlGaAs buried layer (current blocking layer). The film thickness of the first buried layer 7A is adjusted to 0.2 μm or less.

  Next, the semiconductor light emitting device of the second embodiment will be described with reference to FIG. In addition, the same number is attached | subjected to the component same as the semiconductor light-emitting device of 1st Embodiment.

  The semiconductor light emitting device of the second embodiment has the same configuration except that the layer structure of the buried growth layer 7 in the semiconductor light emitting device of the first embodiment described above is different. That is, in the semiconductor light emitting device of the second embodiment, the buried growth layer 7 has a two-layer structure of the first buried layer 7A and the second buried layer 7B. Specifically, as shown in FIG. 2, the first buried layer 7A is composed of an n-InGaP buried layer (buried buffer layer), and the second buried layer 7B is an n-AlGaAs buried layer (current). Block layer). The film thickness of the first buried layer 7A is adjusted to 0.2 μm or less.

  Next, a semiconductor light emitting device according to a third embodiment will be described with reference to FIG. In addition, the same number is attached | subjected to the component same as the semiconductor light-emitting device of 1st Embodiment.

  The semiconductor light emitting device of the third embodiment has the same configuration except that the layer structure of the buried growth layer 7 in the semiconductor light emitting device of the first embodiment described above is different. That is, in the semiconductor light emitting device of the third embodiment, the buried growth layer 7 has a two-layer structure of the first buried layer 7A and the second buried layer 7B, as in the second embodiment. Specifically, as shown in FIG. 3, the first buried layer 7A is composed of a p-InGaP buried layer (buried buffer layer), and the second buried layer 7B is an n-InGaP buried layer (current). Block layer). The film thickness of the first buried layer 7A is adjusted to 0.2 μm or less.

Next, as a method for manufacturing the semiconductor light emitting device of this example, the semiconductor light emitting device of the first embodiment shown in FIG. 1 will be described as an example. First, an n-Al _0.45 Ga _0.55 As first cladding layer (1.5 μm) 2, a GaAs / Al _0.3 Ga _0.7 As quantum well active layer (0.12 μm) 3, p- Al _0.45 Ga _0.55 As second cladding layer (0.2 μm) 4, p-In _0.5 Ga _0.5 P etching blocking layer (20 nm) 5, p-Al _0.45 Ga _0.55 As third cladding layer (0.5 μm) 6 Are sequentially grown.

Subsequently, the p-Al _0.45 Ga _0.55 As third cladding layer 6 is etched using a mask of the SiNx film at a predetermined location, and the p-Al _0.45 Ga _0.55 As third cladding layer (0.5 μm) 6 is subjected to the mesa. A stripe-shaped ridge forming layer is formed.

When the mesa stripe-shaped ridge formation layer is formed on the etching stop layer 5 by the etching process, a p-In _0.5 Ga _0.5 P buried first layer (as a buried growth layer 7 is formed by metal organic chemical vapor deposition. Embedded buffer layer: 50 nm) 7A, n-In _0.5 Ga _0.5 P embedded second layer (embedded buffer layer: 50 nm) 7B, n-Al _0.55 Ga _0.45 As embedded third layer (current blocking layer: 0. 4 μm) 7C is grown sequentially. Thereafter, the SiNx film of the mask is removed, and a p-Al _0.45 Ga _0.55 As fourth cladding layer (1 μm) 8 is formed on the ridge forming layer by the third cladding layer 6 and the n-AlGaAs buried third layer 7C, and p ^+. A GaAs contact layer (0.7 μm) 9 is successively grown. Then, a pair of electrodes (not shown) are provided outside the substrate 1 and the contact layer 10 to complete the semiconductor light emitting device.

  Thus, in the semiconductor light emitting device according to the present invention, the buried growth layer 7 is composed of at least two types of semiconductor layers, and the first buried layer (embedded first layer) 7A does not contain Al. . Specifically, in each embodiment, the first buried layer 7A is made of InGaP. In the first embodiment, the first buried layer 7A and the second buried layer 7B are made of InGaP, and the third buried layer 7C is made of AlGaAs. In the second embodiment, the first buried layer 7A is made of InGaP, and the second buried layer 7B is made of AlGaAs. In the third embodiment, the first buried layer 7A and the second buried layer 7B are made of InGaP. In the first and third embodiments, the conductivity type of the first buried layer 7A is the same as that of the third cladding layer 6, and the conductivity type is changed from p-type to n-type when the second buried layer 7B is grown. Inverted configuration.

  That is, as the semiconductor light emitting device of this example, in the first embodiment and the second embodiment, a current blocking layer made of AlGaAs (the third buried layer 7C in the first embodiment, the first in the second embodiment, 2 buried layer 7B) and the ridge forming layer made of the third cladding layer 6 between the buried buffer layers made of InGaP (the first buried layer 7A and the second buried layer 7B in the first embodiment). In the second embodiment, since the first buried layer 7A) is provided, no non-growth portion is produced during buried growth and no light is absorbed, so that the device performance is improved.

  In the first embodiment and the third embodiment, the conductivity type of the first buried layer 7A of the buried growth layer 7 is the same as that of the third cladding layer 6, and the second buried layer 7B is conductive during the growth. The type is inverted from p-type to n-type. As a result, the regrowth interface and the pn junction interface are separated from each other, and a pn junction is realized in the same composition so that no interface state is formed. As a result, leakage current through the growth interface can be greatly reduced, and laser characteristics such as device breakdown voltage are improved.

  Next, a semiconductor light emitting device according to a fourth embodiment will be described with reference to FIG. Unlike the ridge embedding structure of the first to third embodiments described above, the semiconductor light emitting device of the fourth embodiment has an internal stripe structure.

As shown in FIG. 4, the semiconductor light emitting device of the fourth embodiment includes a substrate 1, a first cladding layer 2, a quantum well active layer 3, a second cladding layer 4, an etching blocking layer 5, a current blocking layer 11, a buried layer. The buried buffer layer 7D, the third cladding layer 6, and the contact layer 9 are laminated in this order, and electrodes (not shown) are disposed at both ends thereof.

The buried buffer layer 7 </ b> D is a crystal grown so as to be buried in the upper surface of the etching blocking layer 5 exposed by etching the current blocking layer 11, the side surface portion, and the upper surface portion of the current blocking layer 11. In the example of FIG. 4, the buried buffer layer 7 </ b> D is formed of a p-InGaP buried layer (buried buffer layer). The film thickness of the embedded buffer layer 7D is adjusted to 0.2 μm or less.

Next, a method for manufacturing the semiconductor light emitting device of the fourth embodiment will be described. First, an n-Al _0.45 Ga _0.55 As first cladding layer (1.5 μm) 2, a GaAs / Al _0.3 Ga _0.7 As quantum well active layer (0.12 μm) 3, and a p− Al _0.45 Ga _0.55 As second cladding layer (0.25 μm) 4, p-In _0.5 Ga _0.5 P etching blocking layer (0.1 μm) 6, n-Al _0.55 Ga _0.45 As current blocking layer (0.5 μm) 11 are sequentially formed by epitaxial growth.

Subsequently, a SiNx film is deposited on the surface of the current blocking layer 11 by a plasma CVD method, and a window of the SiNx film at the stripe portion is opened by a photolithography method. Then, the current blocking layer 11 in the stripe portion is etched to form the stripe portion, and then the SiNx film is removed. Thereafter, buried buffer layer 7D, the third cladding layer 6, the contact layer 9 is epitaxially grown. Then, a pair of electrodes (not shown) are provided outside the substrate 1 and the contact layer 9 to complete the semiconductor light emitting device.

  As described above, the semiconductor light emitting device of the fourth embodiment has a structure in which InGaP is grown to a thickness of 0.2 μm or less as an initial layer during the buried growth of the stripe portion. Similar to the semiconductor light emitting device of the third embodiment, no non-growth portion is produced during buried growth and no light is absorbed, so that the device performance is improved.

  As an etching solution for forming the ridge forming layer in the example shown in FIGS. 1 to 3 and the stripe portion in the example shown in FIG. 4 by selective etching, sulfuric acid (water: hydrogen peroxide solution: sulfuric acid = 1: 1: 3 (25 ° C.)).

  In the example shown in FIGS. 1 to 4, the buried buffer layer is described as being composed of InGaP, but the same effect can be obtained even when the buried buffer layer is composed of InGaAsP.

It is sectional drawing which shows 1st Embodiment of the semiconductor light-emitting device based on this invention. It is sectional drawing which shows 2nd Embodiment of the semiconductor light-emitting device based on this invention. It is sectional drawing which shows 3rd Embodiment of the semiconductor light-emitting device based on this invention. It is sectional drawing which shows 4th Embodiment of the semiconductor light-emitting device based on this invention. 2 is a cross-sectional view of a semiconductor laser disclosed in Patent Document 1. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 1st clad layer 3 Quantum well active layer 4 2nd clad layer 5 Etching stop layer 6 3rd clad layer (ridge formation layer)
6a side
7 buried growth layer 7A first buried layer 7B second buried layer 7C third buried layer
7D buried buffer layer 8 Fourth cladding layer 9 Contact layer 11 Current blocking layer

Claims (3)

In a semiconductor light emitting device in which a current blocking layer containing Al is arranged as a buried growth layer on a side of a ridge forming layer which is made of an AlGaAs material and is cut out in a mesa stripe shape on a GaAs substrate (1). ,
A buried buffer layer (7A) made of InGaP or InGaAsP is formed directly on the surface portion of the side of the ridge-formed layer cut out in the mesa stripe shape, and the current blocking layer containing Al above the buried buffer layer A semiconductor light emitting element characterized in that is formed. In a semiconductor light emitting device in which a current blocking layer containing Al is arranged as a buried growth layer on a side of a ridge forming layer which is made of an AlGaAs material and is cut out in a mesa stripe shape on a GaAs substrate (1). ,
The buried growth layer includes a plurality of buried buffer layers made of InGaP or InGaAsP between the current blocking layer and the ridge forming layer, and the buried buffer layer is a first buried layer. The semiconductor light emitting device is characterized in that the conductivity type is the same as that of the cladding layer constituting the ridge forming layer, and the conductivity type is inverted when the second buried layer is grown. An active layer (3), an etching stop layer (5), and a current blocking layer (11) are sequentially formed on the GaAs substrate (1), and a part of the current blocking layer is selectively removed by etching. In the semiconductor light-emitting device made of an AlGaAs-based material, the Al layer-containing cladding layer (6) is formed above the current-blocking portion and the current blocking layer.
A buried buffer layer (7D) made of InGaP or InGaAsP is formed directly on the selectively etched portion and on the surface of the current blocking layer, and a cladding layer containing Al is formed above the buried buffer layer. A semiconductor light-emitting element formed.

Images