KR102035292B1 - Light emitting diode having improved esd characteristics - Google Patents

Abstract

A light emitting diode having improved electrostatic discharge characteristics is disclosed. The light emitting diode includes an n-type contact layer; p-type contact layer; an active region interposed between the n-type contact layer and the p-type contact layer and including a barrier layer and a well layer; And a carrier retention region located between the n-type contact layer and the active region and in contact with the active region. This carrier holding region has a bandgap adjusting layer with an energy bandgap adjusted to prevent carriers therein from diffusing into the active region. Accordingly, it is possible to provide a light emitting diode having improved electrostatic discharge characteristics while preventing current leakage.

Description

LIGHT EMITTING DIODE HAVING IMPROVED ESD CHARACTERISTICS}

The present invention relates to light emitting diodes, and more particularly to light emitting diodes having improved electrostatic discharge characteristics.

In general, gallium nitride-based semiconductors are widely used in ultraviolet light, blue / green light emitting diodes or laser diodes as a light source for full-color displays, traffic lights, general lighting and optical communication devices. The gallium nitride-based light emitting device includes an active layer having an InGaN-based multi-quantum well structure positioned between n-type and p-type gallium nitride-based semiconductor layers.

1 is a cross-sectional view illustrating a conventional light emitting diode, FIG. 2 is an enlarged cross-sectional view of an active region of FIG. 1, and FIG. 3 is a schematic energy band diagram for explaining an energy band gap of the light emitting diode of FIG. 1. to be.

1 and 2, the light emitting diode includes a substrate 11, a buffer layer 13, an n-type contact layer 15, an active region 17, a p-type contact layer 19, and an n-electrode 21. ) And p-electrode 23.

The conventional light emitting diode includes the active region 17 of the multi-quantum well structure between the n-type contact layer 15 and the p-type contact layer 19 to improve the luminous efficiency, and the InGaN well in the multi-quantum well structure The In content of the layer may be adjusted to emit light of a desired wavelength.

The n-type contact layer 17 typically has a doping concentration in the range of 1 × 10 ¹⁸ / cm 3 to 1 × 10 ¹⁹ / cm 3 and serves to supply electrons. On the other hand, the well layer 17w and the barrier layer 17b in the active region 17 are generally formed of an undoped layer in order to prevent current leakage and achieve good crystal quality. Even when doping in the active region 17, the first barrier layer 17b is doped at a concentration of about 1 × 10 ¹⁹ / cm 3 or less to prevent current leakage.

Since the doping concentration of the predetermined region between the active region 17 and the n-type contact layer 15 is low to prevent current leakage, the depletion region is enlarged into the n-type contact layer 15. This depletion region is further increased with increasing doping concentration in the p-type contact layer 19. The enlargement of the depletion region increases the effective distance d between the n-type contact layer 15 and the p-type contact layer 19. On the other hand, since the capacitance C of the capacitor is inversely proportional to the distance d, the enlargement of the depletion region is the capacitance C of the capacitor formed between the n-type contact layer 15 and the p-type contact layer 19. Decrease). The reduction of the capacitance C consequently worsens the electrostatic discharge characteristics of the light emitting diode.

Meanwhile, in order to improve the electrostatic discharge characteristic of the light emitting diode, as shown in FIG. 3, a portion of the n-type contact layer 15 in contact with the active region 17 or the first barrier layer 17b has a high concentration of 1E19 / cm 3 or more. Doping Si may be considered. However, as described above, since the carriers generated by the high concentration doping easily move into the active region 17, the leakage current of the light emitting diode increases, thereby deteriorating the electrical characteristics of the light emitting diode.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light emitting diode having improved electrostatic discharge characteristics without increasing leakage current.

A light emitting diode according to an embodiment of the present invention, an n-type contact layer; p-type contact layer; An active region interposed between the n-type contact layer and the p-type contact layer and including a barrier layer and a well layer; And a carrier holding region positioned between the n-type contact layer and the active region in contact with the active region and for holding a carrier. The carrier holding region has a bandgap adjusting layer in which an energy bandgap is adjusted to prevent carriers therein from diffusing into the active region.

It is possible to prevent the depletion region from expanding into the n-type contact layer by the carrier holding region, thereby ensuring sufficient capacitance of the light emitting diode, thereby providing a light emitting diode having improved electrostatic discharge characteristics. have. Furthermore, current leakage of the light emitting diode can be prevented by preventing carriers in the carrier holding region from being diffused into the active region.

In one embodiment, the bandgap adjusting layer may have a wider bandgap than the well layer and a narrower bandgap than the barrier layer. In addition, the carrier holding region may include a plurality of bandgap adjusting layers. Further, the bandgap control layer may have a Si doping concentration in the range of 1E19 / cm 3 to 1E21 / cm 3.

Since the bandgap adjusting layer has a narrower bandgap than the barrier layer, carriers can be retained in the bandgap adjusting layer to prevent current leakage.

In another embodiment, the carrier retention region includes a heavily doped layer having a Si doping concentration in the range of 1E19 / cm 3 to 1E21 / cm 3, wherein the bandgap adjusting layer is positioned between the heavily doped layer and the active region. Can be. Furthermore, the bandgap adjusting layer may have a wider bandgap than the barrier layer. The heavily doped layer may have a bandgap equal to or narrower than the barrier layer.

Since the bandgap adjusting layer has a wider bandgap than the barrier layer, carriers can be prevented from diffusing from the heavily doped layer into the active region, thereby preventing current leakage of the light emitting diode.

In some embodiments, the well layer may be formed of InGaN, the barrier layer may be formed of GaN, and the bandgap control layer may be formed of InGaN containing less In than the well layer. Here, the band gap control layer may have a Si doping concentration in the range of 1E19 / cm 3 to 1E21 / cm 3.

In other embodiments, the well layer may be formed of InGaN, the barrier layer may be formed of GaN, and the band gap control layer may be formed of AlGaN. Further, the carrier holding region may further include a high concentration GaN layer having a Si doping concentration in the range of 1E19 / cm 3 to 1E21 / cm 3. In addition, the bandgap control layer may be located between the high concentration GaN layer and the active region.

According to embodiments of the present invention, by disposing a carrier holding region between the n-type contact layer and the active region, it is possible to retain the carrier and to prevent diffusion of the carrier into the active region, thereby preventing current leakage. While providing a light emitting diode capable of improving the electrostatic discharge characteristics.

1 is a schematic cross-sectional view for describing a conventional light emitting diode.
FIG. 2 is an enlarged schematic cross-sectional view of the active region of FIG. 1.
FIG. 3 is a schematic energy band diagram for describing a band gap of the light emitting diode of FIG. 1.
4 is a cross-sectional view illustrating a light emitting diode according to an embodiment of the present invention.
5 is an enlarged schematic cross-sectional view of the active region of FIG. 4.
FIG. 6 is a schematic energy band diagram for describing a band gap of the light emitting diode of FIG. 4.
7 is a schematic energy band diagram for describing a light emitting diode according to still another embodiment of the present invention.
8 is a schematic energy band diagram for describing a light emitting diode according to another embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention; The following embodiments are provided as examples to ensure that the spirit of the present invention can be fully conveyed to those skilled in the art. Accordingly, the present invention is not limited to the embodiments described below and may be embodied in other forms. In the drawings, widths, lengths, thicknesses, and the like of components may be exaggerated for convenience. Like numbers refer to like elements throughout.

4 is a cross-sectional view illustrating a light emitting diode according to an embodiment of the present invention, FIG. 5 is a schematic cross-sectional view showing an enlarged active area of FIG. 4, and FIG. 6 illustrates a band gap of the light emitting diode of FIG. 4. A schematic energy band diagram for this purpose. In FIG. 6, only a conduction band is shown for convenience of description.

4 and 5, the light emitting diode includes a substrate 11, a buffer layer 13, an n-type contact layer 15, a carrier holding region 16, an active region 17, and a p-type contact layer 19. ), n-electrode 21 and p-electrode 23. In addition, the light emitting diode may include a p-type cladding layer (not shown) between the active region 17 and the p-type contact layer 19.

The substrate 51 is a substrate for growing a gallium nitride-based semiconductor layer, and is not particularly limited, such as a sapphire substrate, a SiC substrate, a spinel substrate, a silicon substrate, a GaN substrate, and may be, for example, a patterned sapphire substrate (PSS).

The buffer layer 13 may include a low temperature buffer layer and a high temperature buffer layer. The low temperature buffer layer may be formed of, for example, (Al, Ga) N at a low temperature of 400 ° C. to 600 ° C., in particular, GaN or AlN. The high temperature buffer layer is a layer for alleviating defects such as dislocations between the substrate 11 and the n-type contact layer 15, and is grown at a relatively high temperature. The high temperature buffer layer may be formed of, for example, undoped GaN.

The n-type contact layer 15 is formed of a gallium nitride based semiconductor layer doped with n-type impurities, such as Si. The n-type contact layer may be formed of a single GaN layer, but is not limited thereto, and may be formed of multiple layers. The Si doping concentration doped in the n-type contact layer may be in the range of about 1 × 10 ¹⁸ / cm 3 to 1 × 10 ¹⁹ / cm 3.

The active region 17 may have a multi-quantum well structure in which the barrier layer 17b and the well layer 17w are alternately stacked. Although four well layers 17w are shown in FIG. 5, fewer but more well layers 17w may be used. The barrier layer 17b may be formed of a gallium nitride based semiconductor layer having a wider band gap than the well layer 17w, for example, GaN, InGaN, AlGaN, or AlInGaN. The well layer 17w has a narrower bandgap than the barrier layer 17b. The well layer 17w may also be formed of a gallium nitride based semiconductor layer, such as InGaN, having a narrower bandgap than the n-type contact layer 15. The In composition ratio in the well layer 17w is determined by the desired light wavelength. The first layer of active region 17 is barrier layer 17b and the last layer may be barrier layer 17b or well layer 17w.

The barrier layer 17b and the well layer 17w may be formed of an undoped layer which is not doped with impurities to improve the crystal quality of the active region 17, but the 1E19 may be formed in some or the entire active region to lower the forward voltage. Impurities up to / cm 3 may be doped.

Meanwhile, the carrier holding region 16 is located between the n-type contact layer 15 and the active region 17 and is in contact with the active region 17. The carrier retention region 16 may be comprised of a bandgap adjustment layer 16w with an energy bandgap adjusted to prevent carriers from diffusing into the active region 17 as shown in FIG. 6. That is, the bandgap adjustment layer 16w has a narrower bandgap than the barrier layer 17b and a bandgap is adjusted to have a wider bandgap than the well layer 17w. In addition, the bandgap adjusting layer 16w may have a narrower bandgap than the n-type contact layer 15. The bandgap adjusting layer 16w is in contact with the first barrier layer 17b. The bandgap adjusting layer 16w also has a Si doping concentration in the range of 1E19 / cm 3 to 1E21 / cm 3. For example, the barrier layer 17b may be formed of GaN, the well layer 17w may be formed of InGaN, and the bandgap adjusting layer 16w may have InGaN having a smaller In content than that of the well layer 17w. It can be formed as.

The p-type contact layer 19 is positioned on the active region 17. In addition, a p-type cladding layer (not shown) may be interposed between the active region 17 and the p-type contact layer 19. The p-type cladding layer may be AlGaN. In addition, the p-type contact layer 19 may be a multi-layer structure including a single layer of GaN or a GaN layer.

Meanwhile, the n-electrode 21 is in electrical contact with the n-type contact layer 15, and the p-electrode 23 is in electrical contact with the p-type contact layer 19.

According to the present embodiment, since the bandgap adjusting layer 16w in contact with the active region 17 has a high concentration of Si doping, it is possible to prevent the depletion region from expanding into the n-type contact layer 15. The capacitance C between the n-type contact layer 15 and the p-type contact layer 19 may be increased to improve the electrostatic discharge characteristics of the light emitting diode. Furthermore, the bandgap adjusting layer 16w may be used to prevent carriers therein from diffusing into the active region 17, thereby preventing current leakage of the light emitting diode.

7 is a schematic energy band diagram for describing a light emitting diode according to still another embodiment of the present invention.

Referring to FIG. 7, the light emitting diode according to the present embodiment is generally similar to the light emitting diode described with reference to FIGS. 4 to 6, but the carrier holding region 16 includes a plurality of bandgap adjusting layers 16w. There is a difference.

The plurality of bandgap adjusting layers 16w each have a narrower bandgap than the barrier layer 17b and a wider bandgap than the well layer 17w. Further, each bandgap adjusting layer 16w has a Si doping concentration in the range of 1E19 / cm 3 to 1E21 / cm 3 as described with reference to FIG. 6.

The plurality of bandgap adjusting layers 16w may have the same bandgap, but are not limited thereto and may have different bandgaps. The number, width, doping concentration, and bandgap of the plurality of bandgap adjusting layers 16w may be adjusted in various ways.

According to this embodiment, by adopting the plurality of bandgap adjusting layers 16w, it is possible to effectively prevent the depletion region from expanding and also to easily prevent current leakage.

8 is a schematic energy band diagram for describing a light emitting diode according to another embodiment of the present invention.

Referring to FIG. 8, the light emitting diode according to the present embodiment is generally similar to the light emitting diode described with reference to FIGS. 4 to 6, but there is a difference in the band structure of the carrier holding region 16.

That is, the carrier holding region 16 according to the present embodiment includes a high concentration doping layer 16h and a bandgap adjusting layer 16b. The heavily doped layer 16h may have a Si doping concentration in the range of 1E19 / cm 3 to 1E21 / cm 3, may have a bandgap equal to or narrower than the barrier layer 17b, and may also have an n-type contact layer 15. It may have a bandgap equal to or narrower than. For example, the barrier layer 17b may be formed of GaN, the well layer 17w may be formed of InGaN, and the heavily doped layer 16h may be formed of GaN.

Meanwhile, the bandgap adjusting layer 16b is positioned between the high concentration doping layer 16h and the active region 17. The bandgap adjusting layer 16b has a wider bandgap than the barrier layer 17b and may be formed of, for example, AlGaN. The bandgap adjusting layer 16b prevents carriers in the heavily doped layer 16h from diffusing into the active region 17 to prevent current leakage.

Experimental Example

Epilayers were grown using MOCVD equipment to produce light emitting diodes having a size of about 600 × 600 μm ² . All other conditions were the same, Comparative Example 1 doped Si to less than 1E19 / cm 3 in the first barrier layer, Comparative Example 2 doped Si to about 1E19 / cm 3 in the first barrier layer, and Comparative Example 3 The barrier layer was doped with Si at 1.5E19 / cm 3, and the embodiment forms a bandgap control layer (16w: quasi-well layer) having an In content of approximately 4% less than the well layer 17w before the first barrier layer, and the band Si of about 1.5E19 / cm 3 was doped into the gap control layer 16w.

At the wafer level, the reverse current Ir (@ -5V) did not show a large difference between Comparative Examples 1 and 2, but Comparative Example 3 showed a reverse current value of 10 times or more that of Comparative Example 1. Even at the chip level, the reverse current Ir (@ -5V) did not show a large difference between Comparative Examples 1, 2 and Examples, but Comparative Example 3 showed a reverse current value of three times or more that of Comparative Example 1.

On the other hand, as a result of the ESD test, Comparative Example 1 showed an ESD yield of about 30% (chip yield in a good state after the ESD test), Comparative Example 2 55.7%, Comparative Example 3 66.0%, Example 78.5% ESD yields are shown.

As a result, it can be seen that the embodiment according to the present invention exhibits the best ESD yield without worsening current leakage.

11 substrate, 13 buffer layer, 15 n-type contact layer, 15h high concentration doping layer,
16 carrier retention region, 16w bandgap adjustment layer (highly doped layer),
16b: bandgap adjusting layer, 16h high concentration doping layer, 17 active regions,
17b barrier layer, 17w well layer, 19 p-type contact layer, 21 n-electrode, 23 p-electrode

Claims (11)

n-type contact layer;
p-type contact layer;
An active region interposed between the n-type contact layer and the p-type contact layer and including a barrier layer and a well layer; And
A carrier holding region positioned between the n-type contact layer and the active region and in contact with the active region to hold a carrier,
The carrier holding region is a high concentration doping layer having a Si doping concentration in the range of 1E19 / cm 3 to 1E21 / cm 3 higher than the Si doping concentration in the n-type contact layer, and carriers inside the high concentration doping layer diffuse into the active region. Has a bandgap adjusting layer in which the energy bandgap is adjusted to prevent the
The heavily doped layer has a narrower bandgap than the barrier layer,
The bandgap adjusting layer has a wider bandgap than the barrier layer and is positioned between the heavily doped layer and the active region. The method according to claim 1,
A light emitting diode further comprising a substrate positioned below the n-type contact layer. The method according to claim 2,
An n-electrode electrically connected to the n-type contact layer; And
And a p-electrode electrically connected to the p-type contact layer. The method according to claim 1,
And a p-type cladding layer interposed between the active region and the p-type contact layer. delete delete delete The method according to claim 1,
The well layer is formed of InGaN, the barrier layer is formed of GaN. delete The method according to claim 1,
The well layer is formed of InGaN, the barrier layer is formed of GaN, the band gap control layer is formed of AlGaN. delete

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