JPS6132485A - Semiconductor light emitting element - Google Patents

Abstract

PURPOSE:To obtain the titled element of high reliability capable of high-speed pulse modulation by a method wherein semiconductor buffer layer of P-conductivity type having a carrier concentration of less than a specific value at the part of the second current stricture section is interposed between the first current stricture section and the second one with a larger area of current stricture. CONSTITUTION:A current stricture layer 4 having the first current stricture section 41, a semiconductor buffer layer 5, and the second current stricture section 61 with a larger area of current stricture than that of the first current stricture section 41 are successively formed above the active layer 2 contributed to light emission, and the semiconductor buffer layer 5 at the part except the region in contact with at least the second current stricture section 61 is turned into P-conductivity type with a carrier concentration of less than 1X10<18>cm<-3>. Thereby, because the diameter of the current stricture part 61 is much larger than that of the current stricture part 41, the stress at the edge of the insulation film 6 is not exerted in the periphery of the light emitting part; then, high reliability of the element can be obtained. Besides, the resistivity of the semiconductor buffer layer 5 except the current-injected section 51 is much higher; therefore, the leakage of high frequency current flowing through a P-N junction capacitor parasitic in the current stricture layer 4 can be kept small to a degree of exerting no effect on the response characteristic of the element.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a semiconductor light emitting device.

(Prior art and its problems) Semiconductor light emitting devices such as semiconductor laser devices and light emitting diodes have the characteristics of being capable of high output and high speed modulation with low power consumption, and are widely used in optical fiber communications. Such small power consumption.

In order to produce features such as high output and high speed modulation, above all, an efficient current sandwiching structure to the active layer is required, and many structures have been studied in the past.

However, although the conventional current sandwiching structure is sufficient in a low frequency range, it is insufficient in a high frequency range, and has the drawback of deteriorating high-speed modulation characteristics. In other words, in the case of a trench-embedded semiconductor laser device, in which the active layer is buried in a stripe pattern and a current blocking layer is placed close to the active layer, high-frequency current leaks into the top semiconductor layer because the spreading resistance of the top semiconductor layer is small. , p of the current blocking layer
If the n-junction capacitance is large, it has the disadvantage that the modulation characteristics in the high frequency range deteriorate. Further, surface-emitting light emitting diodes in which current is injected by a circular current injection part also have the drawback that the modulation characteristics in the high frequency range are degraded due to similar parasitic capacitance. On the other hand, in order to reduce leakage of high-frequency current to the top layer of the semiconductor, an insulating film is formed on the top of the semiconductor layer except for the current injection part, thereby reducing parasitic capacitance and improving response characteristics. is also known, but in this structure, the stress on the edges of the insulating film due to the fact that the insulating film is partially formed on top of the top semiconductor layer accelerates the deterioration of the crystal quality of the active layer due to current conduction, making it difficult to put it into practical use. However, it has the disadvantage that a semiconductor light emitting device cannot be obtained.

(Proceedings of the 44th Japan Society of Applied Physics Academic Conference 25a-
P-8) (Objective of the Invention) An object of the present invention is to eliminate the above-mentioned drawbacks and provide a highly reliable semiconductor light emitting device that enables high-speed response.

(Structure of the Invention) A semiconductor light emitting device obtained according to the present invention includes an active layer that participates in light emission, a current confinement layer having a first current confinement portion above the active layer, a semiconductor buffer layer, and A second current confinement portion having a larger current confinement area than the first current confinement portion is sequentially formed, and at least a portion of the semiconductor buffer layer excluding a region in contact with the second current confinement portion is IX.
It is characterized by having a P-type trench electric type with a carrier concentration lower than 10"cm-".

(Example) Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a cross section of an embodiment according to the present invention. In this embodiment, an active layer 2. epitaxially grown on a semiconductor substrate 1. Cladding layer 3゜first current confinement part 4
4. A current confinement layer containing 1. Semiconductor buffer layer 5 including fi current injection part 51 and insulating film 6 including second current confinement part 61
．． An n-side electrode 7 including a light extraction window 71. It is composed of a p-side electrode 8. The semiconductor substrate 1 has an (It)0) orientation and is made of InP doped with Sn I x 10"crn-'
The active layer 2 has a thickness of 7X Zn.
10 cm Doped In0.74G”0.2
Made from 6A80.56P0.44 thickness 0.5 fim
The p cladding layer 3 is made of InP doped with 1×10 crn of Zn and has a thickness of 1 μm.
is doped with 1×10cIn and 71cIn0.85G”
Constructed from O, IgA8G, 36PO, g4, thickness 0.5μ
It is m. The semiconductor buffer layer 5 is doped with Zn 7'
m In(L84G"0.16A80.36'P0.6
4, and the lower the carrier concentration, the better.
The thinner the layer thickness, the better; however, in the examples, from the viewpoint of manufacturing yield, the carrier concentration is 5×10 cm and the layer thickness is 0.5 μm. The insulating film 6 is formed from stow and has a thickness of 0.3 μm on the side 1! The electrode 7 is Au-Qe-Ni.
Made of alloy, thickness 0.3μm, pHllE electrode 8 is A
It is made of u-Zn alloy and has a thickness of 0.3 μm. The first current blocking part 41 and the current injection part 51 have a diameter of 20/jfi.
The selective diffusion of Zn is carried out in the current blocking layer 4 and the semiconductor buffer layer 5.
It is formed by applying it inside. The second current confinement portion 61 is formed by etching the insulating film 6 to a diameter of 30 μm, and the light extraction window 71 is formed by etching the insulating film 6 to a diameter of 30 μm.
It is formed by etching and removing a diameter of 120 μm. During operation, this embodiment operates as a surface-emitting type light emitting diode in which current is constricted and injected into the active layer 2 by the first current confining portion 41 having a diameter of 20 μm, and light is extracted from the light extraction window 71.

In the practical row, the diameter of the second current interlocking part 61 is sufficiently larger than the diameter of the first current interlocking part 41, so that the edge of the insulating film due to the insulating film being partially formed on the uppermost semiconductor layer. High reliability of the device can be obtained because stress is not applied to the vicinity of the light emitting part.

On the other hand, in the direct current and low frequency range, the current injected into the active layer 2 is constricted and injected by the first current confinement part 41 consisting of a reverse biased pn junction, but in the high frequency range, the current injected into the active layer 2 is Due to the large pn junction capacitance parasitic to the semiconductor buffer layer 5, leakage of high frequency current flowing through the resistor from the second interposed current intervening portion 61 causes response deterioration.

In this embodiment, since the semiconductor buffer layer 5 excluding the current injection part 51 has a P-type trench conductivity type lower than 1×10 cm 2 , its resistivity is sufficiently high, and the p-side electrode 8.
MIS'll consisting of an insulating film 6 and a semiconductor buffer layer 5
-* is sufficiently small that it does not affect the response characteristics of the element, so the leakage of high-frequency current flowing through the pn junction parasitic to the current collapse layer 4 does not affect the response characteristics of the element. It is possible to keep it as small as possible. For example, when the size of the device is 300 μm square, the semiconductor buffer layer 5 is not sandwiched over the first current confinement portion 41, and the second current confinement portion 61 is directly formed on the device. In this case, the parasitic capacitance is approximately 2007)p, which causes a large deterioration of the response characteristics, and the modulation speed is also limited to about 100 Mb/s, but in the embodiment to which the present invention is applied, the parasitic capacitance is effectively reduced to approximately 20, enabling high-speed pulse modulation of 200 Mb/s or more.

Note that the present invention is applicable not only to surface-emitting light emitting diodes but also to all semiconductor light emitting devices such as semiconductor laser devices. Semiconductor materials and compositions do not need to be limited to the above-mentioned embodiments, and can be applied to group 1-v compound semiconductors of any composition. There is no need to limit the impurities, insulating film materials, and electrode metal materials to those in the above-mentioned embodiments. Further, the current sandwiching structure is not limited to the structure shown in this embodiment, but can be applied to any structure as long as it has the function of supplying current.

(Effects of the Invention) Finally, to summarize the features of the present invention, at least a second current By sandwiching a semiconductor buffer layer of P-type conductivity type in which the carrier concentration in the narrow part is lower than lXl0 cm, a highly reliable semiconductor light-emitting device capable of reducing parasitic capacitance and performing high-speed pulse modulation can be obtained. That's true.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention. In the figure, 1 is a semiconductor substrate, 2 is an active layer, 3 is a cladding layer, 4 is a current blocking layer, and 41 is a first current blocking portion. 5 is a semiconductor buffer layer, 51 is a current injection part, 6 is an insulating film, 61 is a second current confinement part, and 7 is an n-side electrode. 71 is a light extraction window, and 8 is a p-side electrode.

Claims (1)

[Claims] The active layer is provided with an active layer that participates in light emission, a current trapping layer having a first current trapping portion above the active layer, a semiconductor buffer layer, and a second current trapping layer having a larger current trapping area than the first current trapping portion. Two current confinement portions are sequentially formed, and at least a portion of the semiconductor buffer layer excluding a region in contact with the second current confinement portion has a carrier concentration lower than 1×10^1^5 cm^-^3. A semiconductor light emitting device characterized by having a P-type conductivity type.