TW201322481A - Solid-state light emitting device - Google Patents

Abstract

The present invention provides a solid-state light emitting device, which comprises a first type doping layer, an activation unit, a second type doping layer, and an electrode unit. The activation unit is formed on the first type doping layer, and sequentially formed with a plurality of barrier layers along the direction away from the first type doping layer and a plurality of well layers respectively sandwiched between two neighbored barrier layers for converting the electric energy into the light energy, while receiving the electric energy. The thickness ratio of each well layer to each barrier layer is less than 0.4 and not larger than 1. The second type doping layer is configured on the activation unit, and has the electricity opposite to the first type doping layer. The electrode unit is electrically connected with the first and second type doping layers and can transmit the external electric energy in association with the activation unit. The present invention employs the predetermined thickness ratio of each well layer to each barrier layer to increase the combination probability of electron-hole pairs, so as to enhance the quantum efficiency inside the device and further enhance the light emitting brightness for the device.

Description

Solid state light emitting element

The present invention relates to a light-emitting element, and more particularly to a solid-state light-emitting element.

In solid-state light-emitting elements, particularly light-emitting diodes, the probability of recombination of electron-hole pairs is an element that determines the quantum efficiency of the elements.

Referring to FIG. 1 , in the initial stage of development of a light-emitting diode, the light-emitting diode includes a substrate 11 , an n-type doped layer 12 formed on the substrate 11 , and a n-type doped layer formed thereon. An active layer 13 on the doped layer 12, a p-type doped layer formed on the active layer 13, and a n-doped layer 12 and The p-type doping layer 14 is electrically connected to transmit the electrode unit 15 from the external electric energy.

When the n-type doped layer 12 and the p-type doped layer 14 are transferred with electric energy via the electrode unit 15, electric energy is formed in the n-type doped layer 12 when passing through the n- and p-type doped layers 12 and 14, respectively. The electrons are located in the hole of the p-type doped layer 14, and the electrons and holes are finally combined with the electron-hole pair in the active layer 13, and the potential energy is released and converted by the recombination of the electron-hole pair. For the light to emit outward.

However, the disadvantage of the light-emitting diode is that the thickness of the single active layer 13 is too thick. Although the electron-hole pair can stay in the active layer 13 for a long time, the wave function of the electron and the hole is easily separated, and the electron - The hole has a low probability of composite, that is, the internal quantum efficiency is extremely low; and if the thickness of the single layer active layer 13 is very thin, the wave function of the electron and the hole overlaps more, but only once with respect to the electron-hole pair The composite opportunity still does not effectively improve internal quantum efficiency.

Referring to FIG. 2, in recent years, the structural development of solid-state light-emitting elements, particularly light-emitting diodes, has been to change the original single active layer layer to include a plurality of barrier layers 162 and most of them respectively. The active layer unit structure 16 of the well layer 161 between adjacent barrier layers 162, by the cooperation of each well layer 161 and the barrier layer 162 having a greatly reduced thickness, when the electrode unit 15 is configured to supply electric energy The electron-hole pair is restricted to the well layer 161 by the high energy barrier layer 162. In the environment where the wave function of the electron and the hole overlaps, there are also multiple layers of the well layer 161 for the electron-hole pair. Combined, to increase the probability of electron-hole pair recombination and bonding, and improve internal quantum efficiency.

The internal quantum efficiency of the light-emitting diode including the multilayer barrier layer 162 and the active layer unit structure 16 of the well layer 161 is compared with the initial single active layer 13 structure of the light-emitting diode, due to the recombination of the electron and hole pairs The probability is increased and the number is significantly improved.

Therefore, it is well known to those skilled in the art that the light-emitting diodes having the active layer unit structure 16 of the multilayer barrier layer 162 and the well layer 161 have a higher internal quantum efficiency, and at the same time, the thinner the thickness of the well layer 161 In addition, the electron hole wave function can be prevented from being excessively separated, and the carrier limitation capability can be enhanced, so that the internal quantum efficiency of the formed components is also high; however, the continuous thinning of the well layers 161 does not completely improve the internals. The quantum effect is mainly due to the fact that the number of carriers that can be accommodated in the well layers 161 is relatively small when the well layer 161 is thinned, and instead, problems such as carrier overflow are derived. Therefore, how to have good carrier limitation and avoid the problem of carrier overflow has become a major issue in this field.

Although the limitation of the carrier is determined by the thickness of the well layer, the thickness of the barrier layer adjacent to either well layer affects the epitaxial quality of the well layer, which in turn affects the overall luminous efficiency of the component.

Therefore, the inventors found that the improvement of internal quantum efficiency is not only to consider the thickness of the well layer, but more importantly, the thickness ratio between the well layer and the barrier layer needs to be considered, and the thickness ratio needs to be within a specific range. Really effective in improving its internal quantum efficiency.

Accordingly, it is an object of the present invention to provide a solid state light emitting device having a high internal quantum efficiency.

Therefore, the solid state light emitting device of the present invention comprises a first type doping layer, an actuating unit, a second type doping layer and an electrode unit.

The actuating unit is disposed on the first doped layer and sequentially forms a plurality of barrier layers away from the first doped layer, and the plurality of layers are respectively sandwiched between the two adjacent barrier layers and receive power Converting electrical energy into a well layer of light energy, the ratio of thickness between each well layer and the barrier layer adjacent to the side of the first type doped layer is not less than 0.4 and not more than 1, the second type doping The layer is disposed on the actuating unit and is opposite to the first doped layer. The electrode unit is electrically connected to the first and second doped layers to cooperate with the actuating unit to transfer electrical energy from the outside.

The effect of the invention is that the predetermined thickness ratio between the well layer and the barrier layer disposed on the first type doped layer is limited to not less than 0.4 and not more than 1, increasing the probability of electron-hole pair recombination In addition, the purpose of improving the internal quantum efficiency of the element and the overall luminance of the element is achieved.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments.

Before the present invention is described in detail, it is noted that in the following description, similar elements are denoted by the same reference numerals.

Referring to FIG. 3, a preferred embodiment of the solid state light emitting device of the present invention comprises a substrate 21, a first doped layer 22 formed on the substrate 21 (ie, an n-type doped layer, in the following, An n-type doped layer is shown, an actuating unit 23 coupled to the n-type doped layer, and a second doped layer 24 formed on the actuating unit 23 (ie, a p-doped layer, in the following In the case of a p-type doped layer, and an electrode unit 25 electrically connected to the n- and p-type doped layers.

The n-type doped layer is disposed on the substrate 21 and is mainly composed of an n-type semiconductor material. In the preferred embodiment, the n-type semiconductor material is n-type gallium nitride (GaN).

The actuation unit 23 forms a plurality of barrier layers 232 and a plurality of well layers 231 from a partial region of the top surface of the n-type doped layer, and a partial region of the top surface of the n-type doped layer is not The actuating unit 23 is covered and exposed; in more detail, the barrier layers 232 and the well layers 231 are alternately stacked from the top surface of the n-type doping layer, and one of the two barrier layers 232 is utilized. The well layer 231 spaces it. Therefore, the actuation unit 23 includes at least two barrier layers 232. In the preferred embodiment, the main material of the well layers 231 is indium gallium nitride, and the main material of the barrier layers 232 is gallium nitride.

Further, in the actuating unit 23, the thickness ratio between each well layer 231 and the barrier layer 232 adjacent to and adjacent to the n-type doped layer side is not less than 0.4 and not more than 1.

The p-type doped layer is formed on the actuating unit 23, which is formed of a p-type semiconductor material. In the preferred embodiment, the p-type semiconductor material is p-type gallium nitride.

The electrode unit 25 includes a first electrode 251 disposed on a top surface of the n-type doped layer and not covered by the actuation unit 23, and a second electrode 252 electrically connected to the p-type doped layer. The first and second electrodes 251, 252 transfer electrical energy from the outside to the n, p-type doped layer.

When the first electrode 251 and the second electrode 252 of the electrode unit 25 receive external electric energy, the electric energy passes through the n, p-type doping layer and the barrier layer 232 from the first and second electrodes 251 and 252. Restricted in the well layer 231, the electron holes confined in the well layers 231 are recombined to generate light energy, and part of the generated light energy is emitted outward through the p-type cladding layer.

When the predetermined ratio of the thickness of the well layer 231 sandwiched between the two adjacent barrier layers 232 to the thickness of the barrier layer 232 on the side close to the n-type doped layer is less than 0.4, an accommodating load is generated. Problems such as low number of sub-headers or overflow of carriers cause poor luminous efficiency.

When the predetermined ratio of the thickness of the well layer 231 sandwiched between the two adjacent barrier layers 232 to the thickness of the barrier layer 232 on the side close to the n-type doped layer is higher than 1, the barrier layers are formed. The process of 232 and the well layers 231 easily causes a lattice constant mismatch between the adjacent barrier layer 232 and the well layer 231, resulting in the presence of compressive stress in the quantum well, resulting in compressive strain; The growth temperature of the barrier layers 232 and the well layers 231 are different, so that the ratio of the thickness between the barrier layers 232 and the adjacent well layers 231 is too high, so that the distribution of indium components in the well layers 231 is also distributed. Not uniform. Therefore, even more, when the predetermined ratio of the thickness of the well layer 231 sandwiched between the two adjacent barrier layers 232 to the thickness of the barrier layer 232 on the side close to the n-type doped layer is higher than 1, The elastic strain energy accumulated in the well layers 231 is too high, and the total free energy and the accumulated stress are easily reduced by the dislocation form, which causes epitaxial defects and also causes low luminous efficiency.

When the predetermined ratio of the thickness of the well layer 231 sandwiched between the two adjacent barrier layers 232 to the thickness of the barrier layer 232 on the side close to the n-type doped layer is not less than 0.4 and not more than 1, the electron and The holes are confined to the well layers 231 without limiting the amount of load that can be limited because the well layer 231 is too thin, or causing the carriers to overflow out of the well layer 231; therefore, the electron-hole pair The high probability of bonding promotes an increase in the internal quantum efficiency of the preferred embodiment and, in turn, increases the overall brightness of the component.

Since the total number of layers of the actuating unit 23 is increased, the overall luminous efficiency of the element is high; therefore, preferably, the actuating unit 23 has a barrier layer 232 of not less than five layers.

In addition, if the total number of layers of the actuating unit 23 is too large, the process time of the actuating unit is infinitely extended, and the disproportionately large spoke increases the manufacturing cost and the total time required to produce the component; therefore, more preferably, the actuating Unit 23 has a barrier layer 232 of no more than 30 layers.

It should be noted that the thickness ratio between each well layer 231 and the barrier layer 232 adjacent to and adjacent to the n-type doped layer side is not less than 0.5 and not more than 1, and each well can be adjusted more accurately. The thickness ratio between the adjacent barrier layers 232 of the layer 231 increases the probability of re-bonding of the electron holes and at the same time has good epitaxial quality.

It is worth mentioning that the thickness of each well layer 231 of the actuating unit 23 is 2.5 nm to 5 nm, and the thickness of the barrier layer 232 of a suitable thickness is matched for the electronic hole of the present invention when the operation is performed. The well layers 231 do not cause the carriers to overflow outside the well layers 231; the well layer 231 of the actuating unit 23 is mainly composed of a gallium indium-based compound having an indium content of 10% to 40%. The present invention can be used to emit light having a wavelength in the range of 430 nm to 490 nm when receiving electric energy.

Referring to FIG. 4, it is specifically illustrated that when the thickness of the well layer 231' closest to the p-type doped layer in the well layers 231 is greater than the average thickness of the remaining well layers 231, the p-type doping is permeable to the nearest neighbor. The well layer 231' of the layer carries more carriers to increase the chance of participating in the electron-hole pair recombination, thereby improving the overall internal quantum efficiency and external luminous efficiency of the LED structure. More preferably, the thickness of the well layer 231' closest to the p-type doped layer is greater than 1.1 times the average thickness of the remaining well layer 231; more preferably, the thickness of the well layer 231' nearest the p-type doped layer When the average thickness of the remaining well layer 231 is less than 3 times, the well layer 231 ′ closest to the p-type doped layer may cooperate with the remaining well layers 231 to carry more carriers first, and then use the remaining well layers 231 to limit the carriers. Bit, increase the overlap of the electron hole wave function to enhance the chance of recombination of the electron hole.

It should be noted that, since the barrier layer 232 and the well layer 231 of the actuation unit 23 of the present invention are formed in an epitaxial manner, excessive stress is generated in the process of forming the layer, when the actuation unit 23 is blocked. When the thickness of the barrier layer 232 ′ closest to the n-type doped layer in the barrier layer 232 is greater than the thickness of the other barrier layer 232 , the excess stress generated in the epitaxial process can be released, and the barrier layer 232 and the barrier layer 232 are The formation 231 is formed without stress obstruction.

It should be noted that the solid-state light-emitting device of the present invention may further add a current current diffusion layer 26 between the p-type doping layer and the second electrode 252, and the current diffusion layer 26 is formed of a transparent and electrically conductive material for transmission. The current entering the current spreading layer 26 is uniformly diffused laterally, and the current available to flow into the actuating unit 23 can be more uniform and comprehensive.

When the first electrode 251 and the second electrode 252 of the electrode unit 25 receive external electrical energy, electrical energy is confined in the well layers 231 from the first and second electrodes 251, 252 and the n, p-type doped layers. The electron holes confined in the well layers 231 are recombined to generate light energy, and part of the generated light energy is emitted toward the outside through the p-type doping layer and the transparent current diffusion layer 26.

Referring to FIG. 5, if the positions of the first electrode 251 and the second electrode 252 of the electrode unit 25 are classified, FIG. 4 is a lateral type light-emitting diode, and FIG. 5 replaces the first electrode 251. The base material 21 is provided on the bottom surface of the n-type doped layer, and is a vertical type light-emitting diode.

In summary, the present invention mainly finds that the existing solid-state components, especially the light-emitting diodes, improve the internal quantum efficiency, and the thinner the well layer 131 is, the lower the thickness ratio of the well layer 131 and the barrier layer 132 is, the wrong direction is developed. It is proposed to control the thickness of the well layer 231 of the actuating unit 23 and the thickness of the barrier layer 232 to a predetermined ratio, and then mix the well layer 231 closest to the p-type doped layer to be thicker to limit the carrier overflow. And the barrier layer 232 closest to the n-type doped layer is thickened to reduce the stress generated during the process of epitaxially moving the actuating unit 23, and the wave function of the electron-hole is overlapped, and The carrier will overflow out of the well layers 231 to increase the chance of electron-hole pair bonding, effectively improve the internal quantum efficiency of the element, and thereby enhance the overall brightness of the element, so that the object of the present invention can be achieved.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

twenty one. . . Substrate

twenty two. . . First doped layer

twenty three. . . Actuating unit

231. . . Well layer

232. . . Barrier layer

231’. . . Well layer closest to the second doped layer

232’. . . Barrier layer closest to the first doped layer

twenty four. . . Second type doping layer

25. . . Electrode unit

251. . . First electrode

252. . . Second electrode

26. . . Current diffusion layer

Figure 1 is a schematic cross-sectional view showing a conventional solid state light-emitting element;

Figure 2 is a cross-sectional view showing the current solid state light-emitting element;

Figure 3 is a cross-sectional view showing a preferred embodiment of the solid state light-emitting device of the present invention;

4 is a cross-sectional view showing a preferred embodiment of the solid state light emitting device of the present invention further comprising a current spreading layer;

Figure 5 is a schematic cross-sectional view showing that the present invention can also be a vertical solid-state light-emitting element.

twenty one. . . Substrate

twenty two. . . First doped layer

twenty three. . . Actuating unit

231. . . Well layer

232. . . Barrier layer

twenty four. . . Second type doping layer

25. . . Electrode unit

251. . . First electrode

252. . . Second electrode

Claims (13)

A solid-state light-emitting device comprising: a first-type doped layer; an actuating unit disposed on the first-type doped layer and sequentially forming a plurality of barrier layers away from the first-type doped layer, and a plurality of a well layer sandwiched between two adjacent barrier layers and converting electrical energy into light energy when receiving electrical energy, and the thickness ratio between each well layer and the barrier layer adjacent to the side of the first type doped layer is not a second doped layer disposed on the actuating unit and having opposite electrical properties to the first doped layer; and an electrode unit and the first and second doped layers Electrically coupled to communicate power from the outside to the actuating unit. The solid-state light-emitting element according to claim 1, wherein the actuating unit has a barrier layer of not less than 5 layers. The solid state light emitting device of claim 2, wherein the actuating unit has a barrier layer of no more than 30 layers. The solid state light emitting device of claim 1, wherein a thickness of the well layer closest to the second type doped layer in the well layers is greater than an average thickness of the remaining well layers. The solid state light-emitting device of claim 1, wherein a thickness of the well layer closest to the second-type doped layer in the well layers is greater than 1.1 times the average thickness of the remaining well layers. The solid state lighting device of claim 5, wherein the thickness of the well layer closest to the second type doped layer in the well layers is less than 3 times the average thickness of the remaining well layers. The solid-state light-emitting device according to claim 1, wherein each of the well layers of the actuating unit has a thickness of 2.5 nm to 5 nm. The solid-state light-emitting device of claim 1, wherein a thickness of the barrier layer closest to the first-type doped layer of the barrier layers is greater than a closest one of the barrier layers to the second type The thickness of the barrier layer of the doped layer. The solid-state light-emitting device of claim 8, wherein a barrier layer closest to the first-type doped layer of the barrier layers is thicker than the second type of the barrier layers The barrier layer of the doped layer has a thickness of 5 nm to 10 nm. The solid-state light-emitting device according to claim 1, wherein the well layer is mainly composed of a gallium indium-based compound having an indium content of 10% to 40%. The solid-state light-emitting device of claim 1, further comprising an epitaxial substrate disposed on a surface of the first-type doped layer away from the active cell, the actuating unit covering the first-type doped layer a portion of the other surface of the surface, the electrode unit includes a first electrode disposed on a surface of the first type doped layer away from the epitaxial substrate that is not covered by the actuation unit, and a portion A second electrode electrically connected to the doped layer. The solid-state light-emitting device of claim 1, wherein the electrode unit comprises a first electrode disposed in a surface of the first-type doped layer away from the actuating unit, and a second type The second electrode electrically connected to the impurity layer. The solid-state light-emitting device according to claim 11 or 12, further comprising a current diffusion layer disposed between the second-type doped layer and the second electrode for laterally uniformly diffusing current.