Patent Application
20180331257
The present invention relates to an infrared light emitting diode and a manufacturing method thereof, and more specifically, to an infrared light emitting diode with improved light emitting efficiency and a manufacturing method thereof.
An infrared light emitting diode having a center wavelength of 940±10 nm (hereinafter, referred to as a center wavelength of 940 nm) has a grown n-type AlxGa1-xAs material and a p-type AlxGa1-xAs material (0.1<x<0.7) with substantially the same lattice constant on a GaAs substrate having a high lattice matching rate and high cost reduction (economic feasibility), and has an active layer including an undoped GaAs quantum barrier and an InGaAs quantum well, in which content of In is adjusted to be less than 10% so as to grow on these layers (the n-type and p-type materials and the quantum barrier), between the grown n-type and p-type materials. Generally, the active layer is a multi-structure configured of an InGaAs quantum well and a GaAs quantum barrier. In addition, a p-type AlxGa1-xAs layer of 3 um or more which is a current diffusion layer is grown on uppermost part to maximize the optical efficiency. Such an infrared light emitting diode having a center wavelength of 940 nm is generally manufactured using metalorganic chemical vapor deposition (MOCVD) for growth of high quality.
However, such a structure causes degradation of efficiency since a strain occurs in the InGaAs used as the quantum well of the active layer due to lattice mismatch with the GaAs layer in the growth process.
Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a method of preventing degradation of efficiency caused by lattice mismatch of an infrared light emitting diode having a center wavelength of 940 nm.
Another object of the present invention is to provide a light emitting diode with improved efficiency by compensating for the lattice mismatch of an infrared light emitting diode having a center wavelength of 940 nm.
To solve the problems described above, the infrared light emitting diode having a center wavelength of 940 nm has an InGaP strain compensation layer between a lower confinement layer and an active layer.
Although the present invention is not limited theoretically, since lattice constants of all the n-type layer, p-type layer, quantum barrier and window layer excluding the InGaAs layer of quantum well almost correspond to that of the GaAs substrate material (for example, Aly0.3Ga0.7As/GaAs:Δα/α≤400 ppm; a change rate with respect to the lattice constant) while the lattice constant change rate between the GaAs layer and the InGaAs layer has a high compressive strain (for example, In0.07Ga0.93As/GaAs:Δα/α≤6,000 ppm; a change rate with respect to the lattice constant), efficiency of the active layer of the light emitting diode can be improved by minimizing the rate of the compressive strain generated in the growth process of the InGaAs active layer by inserting a strain compensation layer under the InGaAs active layer, in which the lattice constant of the strain compensation layer almost corresponds to that of the GaAs material, and the strain compensation layer has a tensile strain rate for compensating for the compressive strain rate through control of the composition ratio between In and Ga.
In the present invention, the InGaP strain compensation layer is preferably an InxGa1-xP layer (0.44≤x≤0.47), further preferably x=0.47, to enhance light emitting efficiency.
In the present invention, the term ‘compressive strain’ means that the active layer has an arcsec lower than the arcsec of the GaAs substrate.
In the present invention, the term ‘tensile strain’ means that the active layer has an arcsec higher than the arcsec of the GaAs substrate.
In the present invention, an infrared light emitting diode having a center wavelength of 940 nm includes a GaAs substrate; a first type AlGaAs lower confinement layer grown on the GaAs substrate; an InGaP strain compensation layer grown on the first type AlGaAs lower confinement layer; an active layer including an InGaAs quantum well grown on the InGaP strain compensation layer; a second type AlGaAs upper confinement layer grown on the active layer; and a p-type window layer and has an upper electrode and a lower electrode respectively on the top surface and the bottom surface of the p-type window layer and the GaAs substrate.
In the present invention, the GaAs substrate is a substrate on which a lower confinement layer grows, and a lower electrode may be formed on the bottom surface of the substrate. In an embodiment of the present invention, the GaAs substrate may be a type the same as that of the first type AlGaAs lower confinement layer, preferably an n-type GaAs substrate, and for example, the n-type GaAs substrate may have a value of 32.9 arcsec.
In the present invention, the AlGaAs lower confinement layer preferably uses a type the same as that of the lower GaAs substrate and preferably has an arcsec value substantially of the same level as the n-type substrate, i.e., ±0.5 of the arcsec value of the n-type substrate. In a preferred embodiment, the ratio between Al and Ga may be controlled so that AlGaAs may have an arcsec value substantially of the same level as the n-type substrate. For example, AlGaAs may be expressed as AlxGa1-xAs, and x may be 0.3.
In the present invention, the active layer may be a multilayered active layer alternatingly stacking an InGaAs quantum well layer and a GaAs quantum barrier layer.
In an embodiment of the present invention, the InGaAs active layer may use a range of 0.07≤x≤0.08 in the InxGa1-xAs layer so as to emit light having a center wavelength of 940 nm, and the range may be controlled slightly according to thickness.
In a preferred embodiment of the present invention, the multilayered active layer may be two or more pairs, preferably three or more pairs, further preferably four or more pairs, and preferably five pairs of InGaAs the quantum well layer and the GaAs quantum barrier.
In the present invention, the upper confinement layer AlGaAs may be expressed as AlxGa1-xAs, and x may be 0.3.
In an aspect of the present invention, there is provided a light emitting diode including a substrate; a lower confinement layer; a strain active layer; an upper confinement layer; and a window layer, wherein a strain compensation layer for compensating for strain of the active layer is further provided between the lower confinement layer and the active layer.
In an aspect of the present invention, there is provided a method of manufacturing a light emitting diode including a substrate; a lower confinement layer; a strain active layer; an upper confinement layer; and a window layer, wherein a strain compensation layer for compensating for strain of the active layer is grown on the lower confinement layer, and the active layer is grown on the strain compensation layer.
In the present invention, it is preferable that a tensile strained compensation layer is formed for the compressively strained active layer and a compressively strained compensation layer is formed for the tensile strained active layer so that efficiency of the light emitting diode may be improved.
Hereinafter, the present invention will be described in detail through an embodiment.
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According to the present invention, the problem according to the strain of an infrared light emitting diode of a center wavelength of 940 nm using a GaAs substrate having a high lattice matching rate and high cost reduction is solved, and thus an infrared diode with improved light emitting efficiency is provided.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2017-0059047 | May 2017 | KR | national |
