KR20020081552A - Light-emitting diode and light-emitting device apparatus employing it - Google Patents

Abstract

an n-type or p-type substrate; A doped region extremely shallowly doped to the opposite side of the substrate by a predetermined dopant so as to emit light by a quantum confinement effect at a p-n junction with the substrate; a resonator for improving wavelength selectivity of light emitted from the p-n junction; Disclosed are a light emitting device and a light emitting device apparatus using the same, including first and second electrodes formed on opposite and substrate surfaces, respectively, to inject holes and electrons.

The disclosed light emitting device has a doped region that is extremely shallowly doped to emit light by quantum confinement effects at its pn junction, and has a resonator structure that resonates only light of a specific wavelength band, thereby providing excellent efficiency. Rather, the wavelength selectivity is greatly improved. In addition, the light emission intensity is amplified by the resonator structure, and the straightness of the emitted light is greatly improved.

Description

Light emitting device and light emitting device apparatus using the same

The present invention relates to a light emitting device capable of achieving high efficiency and a light emitting device apparatus employing the same.

In the silicon semiconductor substrate, logic devices, arithmetic devices, and drive devices can be integrated with high reliability and high integration. Since silicon is cheap, the silicon semiconductor substrate can be realized at a much lower cost than a compound semiconductor, thereby realizing a highly integrated circuit. Therefore, most integrated circuits use silicon (Si) as a base material.

In order to fully utilize the advantages of silicon as described above, researches are being made to make silicon-based light emitting devices so that compatibility with integrated circuits and manufacturing low-cost optoelectronic devices can be realized. It has been experimentally confirmed that porous silicon and nano-crystal silicon have luminescent properties, and research on this is ongoing.

1 is a cross-sectional view of a porous silicon region formed on a bulk monocrystalline silicon surface and an energy band gap between a valence band and a conduction band in the porous silicon region.

Porous silicon may be prepared by placing bulk monocrystalline silicon (Si) in an electrolyte solution containing, for example, hydrofluoric acid (HF), and anodizing the surface of the bulk Si.

When anodizing bulk silicon in hydrofluoric acid solution, a porous silicon region 1 having a plurality of pores 1a: pore is formed on the bulk silicon surface side as shown in FIG. The Si-H bond is more present in the pore 1a portion than in the convex portion 1b: the portion not melted by hydrofluoric acid. The energy band gap between the valence band energy Ev and the conduction band energy Ec in the porous silicon region 1 is opposite to the shape of the porous silicon region 1.

Therefore, the pore portion surrounded by the convex portion in the energy band gap diagram (the convex portion 1b surrounded by the pore portion 1a in the porous silicon region 1 diagram) exhibits a quantum confinement effect, so that the energy of the bulk silicon The band gap is larger than the band gap, and electrons and holes are trapped in the portion to emit light.

For example, in the porous silicon region 1, when the convex portion 1b surrounded by the pores 1a is formed in the form of a single crystal silicon wire having a quantum confining effect, electrons and holes are trapped in the wire to emit light-coupled bonds. Depending on the size (width and length) of the wire, the emission wavelength can range from near infrared to blue. At this time, as shown in FIG. 1, the pore 1a period is, for example, approximately 5 nm and the maximum thickness of the porous silicon region is, for example, about 3 nm.

Accordingly, when a light emitting device based on porous silicon is manufactured and a predetermined voltage is applied to the single crystal silicon on which the porous silicon region 1 is formed, light of a desired wavelength region may be emitted according to the porous characteristics.

However, the light emitting device based on the porous silicon has not yet been secured as a light emitting device, and has an external quantum efficiency (EQE) of about 0.1%.

2 is a cross-sectional view schematically showing an example of a light emitting device using nanocrystal silicon.

Referring to the drawings, a light emitting device using nanocrystal silicon includes a p-type single crystal silicon substrate 2, an amorphous silicon layer 3 formed on the substrate 2, and the amorphous silicon layer 3. The amorphous silicon layer 3 has a layer structure including an insulating film 5 formed on the upper surface and lower and upper electrodes 6 and 7 formed on the lower surface of the substrate 2 and the insulating film 5, respectively. Nanocrystalline silicon 4 in the form of a quantum dot formed therein is provided.

When the amorphous silicon layer 3 is rapidly crystallized by raising the temperature to 700 ° C. in an oxygen atmosphere, nanocrystalline silicon 4 having a quantum dot form is formed. At this time, the thickness of the amorphous silicon layer 3 is 3nm, the size of the nanocrystal silicon 4 is approximately 2 ~ 3nm.

In the light emitting device using the nanocrystal silicon 4 as described above, when the voltage is reversed through the upper and lower electrodes 7 and 6, both ends of the amorphous silicon between the silicon substrate 2 and the nanocrystal silicon 4 are provided. A large electric field is generated in the electrons and holes in the high energy state, and they are tunneled into the nanocrystal silicon 4 to emit light bonds. In this case, the light emission wavelength of the light emitting device using the nanocrystal silicon 4 becomes shorter as the size of the nanocrystal silicon quantum dot is smaller.

The light emitting device using the nanocrystal silicon 4 is difficult to control the size and uniformity of the nanocrystal silicon quantum dot, and the efficiency is very low.

The present invention has been made to solve the above-mentioned disadvantages, and provides a light emitting device having a higher efficiency than the light emitting device using porous silicon and nanocrystal silicon as well as improved light emission wavelength selectivity and a light emitting device device using the same. There is a purpose.

1 is a cross-sectional view of a porous silicon region formed on a bulk monocrystalline silicon surface and an energy band gap between a valence band and a conduction band in the porous silicon region;

2 is a cross-sectional view schematically showing an example of a light emitting device using nanocrystal silicon;

3 is a cross-sectional view schematically showing a light emitting device according to a first embodiment of the present invention;

4 is a cross-sectional view schematically showing a light emitting device according to a second embodiment of the present invention;

FIG. 5A schematically shows the structure of a p-n junction when forming a doped region at an extremely shallow depth by non-equilibrium diffusion, FIG.

FIG. 5B shows an energy band of quantum wells (QW) formed longitudinally and laterally of the surface at the p-n junction site 14 shown in FIG. 5A by non-equilibrium diffusion.

<Description of the symbols for the main parts of the drawings>

11 substrate 13 control film (silicon oxide film)

14 ... p-n junction 15 ... doped region

17 ... first electrode 19 ... second electrode

21 ... First reflector 25 ... Second reflector

A light emitting device according to the present invention for achieving the above object is an n-type or p-type substrate; A doped region extremely shallowly doped to the opposite side of the substrate by a predetermined dopant such that light is emitted by a quantum confinement effect at a p-n junction with the substrate on one surface of the substrate; A resonator for improving wavelength selectivity of light emitted from the p-n junction; In order to inject holes and electrons, the first and second electrodes formed on opposite and one surface of the substrate, respectively.

Here, the resonator may include a first reflecting film formed on an opposite side of the substrate; And a second reflecting film formed on the doped region to form a resonator with the first reflecting film to improve light emission wavelength selectivity, wherein one of the first and second reflecting films has a lower reflectance than the other reflecting film. It is preferable that the light emitted through one reflective film having a low reflectance is emitted.

The second reflective film is preferably a Bragg reflective film formed by alternately stacking materials having different refractive indices.

The first reflective film may be formed on an opposite surface of the substrate, and the first electrode may be formed on an opposite surface of the substrate around the first reflective film.

Alternatively, the first electrode may be formed as a transparent electrode between the opposite surface of the substrate and the first reflective film.

It is preferable to further include a control film on one surface of the substrate to function as a mask when forming the doped region, the doped region is formed to an extremely shallow doping depth.

The substrate is made of a predetermined semiconductor material including silicon, and the control film is preferably a silicon oxide film having an appropriate thickness such that the doped region is formed to an extremely shallow doping depth.

In order to achieve the above object, the present invention relates to a light emitting device device having at least one light emitting element, the light emitting element comprising: an n-type or p-type substrate; A doped region extremely shallowly doped to the opposite side of the substrate by a predetermined dopant such that light is emitted by a quantum confinement effect at a p-n junction with the substrate on one surface of the substrate; A resonator for improving wavelength selectivity of light emitted from the p-n junction; In order to inject holes and electrons, the first and second electrodes formed on opposite and one surface of the substrate, respectively, and are applied to any one of an illumination system and a display system.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 and 4 are cross-sectional views schematically illustrating light emitting devices according to first and second embodiments of the present invention, respectively.

Referring to the drawings, the light emitting device according to the present invention includes a substrate 11, a doped region 15 formed on one surface of the substrate 11, a resonator for improving wavelength selectivity of emitted light, holes and electrons. It comprises a first electrode and a second electrode formed on the opposite surface and one surface of the substrate 11 for injection. In addition, the light emitting device according to the present invention functions as a mask when the doped region 15 is formed, and has a control film 13 for forming the doped region 15 to an extremely shallow depth. It is preferable to further provide on one surface of (11). The control film 13 is necessary to form the doped region 15 of the light emitting device according to the present invention, and may be selectively removed after the doped region 15 is formed.

The substrate 11 is made of a predetermined semiconductor material including silicon (Si), for example, Si, SiC or diamond, and is preferably doped n-type.

The doped region 15 diffuses a predetermined dopant, for example, boron or phosphorous, into the substrate 11 through an opening of the control layer 13 formed on one surface of the substrate 11. The region 11 is doped with the substrate 11, for example, p +.

At least any one of a quantum well, a quantum dot, and a quantum wire at a boundary portion of the doped region 15 with the substrate 11, that is, the pn junction region 14, during doping. The doped region 15 is preferably doped to an extremely shallow depth so that one can be formed to emit light due to the quantum confinement effect.

In this case, a quantum well is mainly formed at the p-n junction 14, and a quantum dot or a quantum line may be formed. In addition, two or more of the quantum wells, the quantum dots, and the quantum lines may be formed in the p-n junction 14. In the following description, quantum wells are formed in the p-n junction 14 for the sake of simplicity. Although it will be described below that the quantum well is formed in the p-n junction site 14, it is considered to mean at least one of quantum wells, quantum dots and quantum lines.

5A shows the structure of the p-n junction site 14 when the doped region 15 is formed to an extremely shallow depth by non-equilibrium diffusion. FIG. 5B shows the energy band of quantum wells (QW) formed longitudinally and laterally of the surface at the p-n junction site 14 shown in FIG. 5A by non-equilibrium diffusion. In FIG. 5B, Ec represents a conduction band energy level, Ev represents a valence band energy level, and Ef represents a Fermi energy level. Such energy levels are well known in the semiconductor related art, and thus a detailed description thereof will be omitted.

As shown in FIGS. 5A and 5B, the p-n junction site 14 has a quantum well structure in which different doping layers are alternately formed, and the well and barrier are, for example, approximately 2 nm and 3 nm.

As such, extremely shallow doping to form the quantum well at the p-n junction 14 may be formed by optimally controlling the thickness of the control layer 13 and the diffusion process conditions.

Due to the proper diffusion temperature during the diffusion process and the modified potential of the surface of the substrate 11, the thickness of the diffusion profile can be controlled, for example, 10-20 nm. A quantum well system will be created. Here, the surface of the substrate 11 is deformed by the thickness of the initial control film and the surface pretreatment and deepens as the process proceeds.

When the substrate 11 is made of a predetermined semiconductor material including silicon, the control layer 13 is a silicon oxide film (SiO ₂ ) having an appropriate thickness such that the doped region 15 is formed to an extremely shallow doping depth. It is preferable. The control film 13 is formed in a mask structure by, for example, forming a silicon oxide film on one surface of the substrate 11 and then etching the opening portion for the diffusion process using a photolithography process.

It is known in the diffusion technology that if the thickness of the silicon oxide film is thicker or lower than the suitable thickness (thousands of kPa), the vacancy mainly affects the diffusion and the diffusion occurs deeply, and the thickness of the silicon oxide film is larger than the proper thickness. At thin or high temperatures, Si self-interstitial mainly affects diffusion, causing deep diffusion. Therefore, when the silicon oxide film is formed to an appropriate thickness in which Si self-interstitial and vacancy are generated at a similar rate, the Si self-interstitial and vacancy are bonded to each other and do not promote diffusion of the dopant, thereby enabling extremely shallow doping. . Here, since physical properties related to vacancy and self-interstitial are well known in the art related to diffusion, a detailed description thereof will be omitted.

Herein, the substrate 11 may be doped with a p-type, and the doped region 15 may be doped with an n + type.

The resonator includes a first reflecting film 21 formed on the opposite side of the substrate 11 and a second reflecting film 25 formed on the doped region 15 to improve emission wavelength selectivity. . In order to maximize the efficiency of light emitted and emitted in a desired direction, the first reflecting film 21 is formed to have a high reflectance (preferably nearly 100%), and the second close to the doped region 15. The reflective film 25 is preferably formed to have a lower reflectance than the first reflective film 21, so that the light emitted from the pn junction portion 14 is emitted through the second reflective film 25. On the contrary, the first reflecting film 21 may be formed to have a lower reflectance than the second reflecting film 25 so that the emitted light may be emitted through the first reflecting film 21.

The first reflective film 21 may be formed of a general reflective film or a Bragg reflective film (DBR). The second reflective film 25 is preferably formed of a Bragg reflective film to reduce the bandwidth of the emission spectrum. The second reflective film 25 is formed in a region excluding the position where the second electrode 19 is formed in the opening portion of the control film 13. Here, the Bragg reflective film is formed by stacking materials having different refractive indices, for example, compound semiconductor materials, alternately by the required number of stacked layers. As long as both the first and second reflecting films 21 and 25 are made of Bragg reflecting films, and as described above, the emitted light is emitted through the second reflecting film 25, the second reflecting film 25 is It is formed with a smaller stacking number than the first reflective film 21 so as to have a lower reflectance than the first reflective film 21.

When the resonator as described above is provided, wavelength selectivity is greatly improved because only light in a specific wavelength band suitable for the resonance condition of the resonator can be amplified and emitted. The resonator is formed under a resonance condition suitable for a wavelength band to emit light.

The first electrode 17 is formed on the opposite surface of the substrate, and the second electrode 19 is formed around the second reflective film 25 on one surface of the substrate 11.

Referring to FIG. 3, which shows a first embodiment of a light emitting device according to the present invention, the first electrode 17 may be positioned between the opposite surface of the substrate 11 and the first reflective film 21. In this case, the first electrode 17 is preferably formed of a transparent electrode using, for example, ITO to transmit light.

Referring to FIG. 4, which shows a second embodiment of a light emitting device according to the present invention, the first reflective film 21 is formed only on a portion where the most reflective effect of the opposite surface of the substrate 11 is large, and the first electrode ( 17 may be formed around the first reflective film 21 on the opposite surface of the substrate 11.

In the light emitting device according to the present invention configured as described above, since the quantum wells capable of dissipation coupling of electrons and hole pairs are formed at the pn junction site 14 of the doped region 15 with the substrate 11, As mentioned above, only light of a desired wavelength band which emits light and meets the resonance condition of the resonator composed of the first and second reflecting films 21 and 25 is amplified and emitted through the second reflecting film 25. Of course, the amount of light emitted and the wavelength depend on the amount of current applied.

That is, the light emitting device according to the present invention emits light as follows. For example, when a power source (voltage or current) is applied through the first and second electrodes 17 and 19, carriers, ie electrons and holes, are injected into the quantum well of the pn junction 14. And recombination through the subband energy levels in the quantum wells. At this time, electroluminescence (EL) of a predetermined wavelength is generated according to the state in which carriers are coupled, and the amount of light generated is generated by the power source (voltage or current) applied through the first and second electrodes 17 and 19. It depends on the century.

At this time, the light emission wavelength of the light emitting device according to the present invention is primarily a micro-cavity due to micro-defects formed on the surface of the substrate 11 (actually, the surface of the doped region 14). cavity). Therefore, by adjusting the size of the very small cavity by the manufacturing process, it is possible to obtain a light emitting device having a desired emission wavelength band.

Herein, the intensity of the electric field emission EL may be amplified when the intensity of the electric field EL is well matched with the resonance wavelength of the microcavity due to the microscopic defect formed on the surface of the substrate 11.

The microcavity is due to the deformed potential due to the micro defects formed on the surface of the doped region 14. Accordingly, by adjusting the modified potential, the quantum well can be modified, and accordingly, the minimum cavity is determined. When the minimum cavity is adjusted, light emission of a desired wavelength band can be obtained.

As described above, the light emitting device according to the present invention generates a quantum confinement effect due to a local change in the charge distribution potential at the pn junction 14 of the extremely shallowly doped region 15, Subband energy level is formed, and has high quantum efficiency.

In addition, the light emitting device according to the present invention has a desired narrow wavelength band suitable for the resonance condition of the resonator composed of the first and second reflecting films 21 and 25 among the light of the wavelength band emitted from the pn junction portion 14. Since only light is amplified, wavelength selectivity is greatly improved.

The light emitting device according to the present invention as described above may be applied as a light emitting device device to a display system or an illumination system, and when applied to the display system or the lighting system, it is possible to obtain more vivid color characteristics than when a conventional light emitting device is applied. The light emitting device apparatus is provided with at least one light emitting element according to the present invention.

When the light emitting device apparatus to which the light emitting element according to the present invention is applied is for a display system, the light emitting device apparatus comprises a plurality of light emitting elements according to the present invention arranged in two dimensions. Since the light emitting device according to the present invention can be formed into a microminiature through a semiconductor manufacturing process using a semiconductor material, it is obvious that it can be applied to a display system, in particular, a flat panel solid state display. In addition, since the light emitting device according to the present invention has greatly improved wavelength selectivity, when each light emitting device constituting the light emitting device device according to the present invention is formed to have a resonance condition suitable for each color pixel of the display system, For example, R, G, B colors can be implemented without a separate color filter. Of course, it is possible to add a color filter to the light emitting device device according to the present invention for clearer color.

When the light emitting device device to which the light emitting device according to the present invention is applied is for a lighting system, the light emitting device device comprises at least one light emitting device according to the present invention in response to the use and illumination requirement of the lighting system. In this case, the light emitting device employed includes a resonator optimized for a desired color.

Since the structure of the light emitting device apparatus to which the light emitting element according to the present invention as described above is applied can be sufficiently inferred from the above description, the illustration thereof is omitted.

The light emitting device according to the present invention as described above has a doped region that is extremely shallowly doped to emit light by quantum confinement effect at its pn junction, and adds a resonator structure that resonates only light of a specific wavelength band Therefore, not only the efficiency is excellent but also the wavelength selectivity is greatly improved. In addition, the light emission intensity is amplified by the resonator structure, and the straightness of the emitted light is greatly improved.

Claims (14)

an n-type or p-type substrate; A doped region extremely shallowly doped to the opposite side of the substrate by a predetermined dopant such that light is emitted by a quantum confinement effect at a p-n junction with the substrate on one surface of the substrate; A resonator for improving wavelength selectivity of light emitted from the p-n junction; And a first electrode and a second electrode formed on opposite and one surface of the substrate to inject holes and electrons, respectively. The method of claim 1, wherein the resonator, A first reflecting film formed on the opposite side of the substrate; And a second reflecting film formed on the doped region to form a resonator with the first reflecting film to improve light emission wavelength selectivity, wherein one of the first and second reflecting films has a lower reflectance than the other reflecting film. And light emitted through one reflective film having a low reflectance. The light emitting device according to claim 2, wherein the second reflecting film is a Bragg reflecting film formed by alternately stacking materials having different refractive indices. The light emitting device of claim 2 or 3, wherein the first reflective film is formed on an opposite surface of the substrate, and the first electrode is formed on an opposite surface of the substrate around the first reflective film. . The light emitting device of claim 2 or 3, wherein the first electrode is formed of a transparent electrode between an opposite surface of the substrate and the first reflective film. The method according to claim 1 or 2, And a control film which functions as a mask when the doped region is formed on one surface of the substrate and allows the doped region to be formed with an extremely shallow doping depth. The method of claim 6, wherein the substrate is made of a predetermined semiconductor material including silicon, The control film is a light emitting device, characterized in that the silicon oxide film having a suitable thickness so that the doped region is formed to an extremely shallow doping depth. A light emitting device device comprising at least one light emitting element, The light emitting device, an n-type or p-type substrate; A doped region extremely shallowly doped to the opposite side of the substrate by a predetermined dopant such that light is emitted by a quantum confinement effect at a p-n junction with the substrate on one surface of the substrate; A resonator for improving wavelength selectivity of light emitted from the p-n junction; And first and second electrodes respectively formed on opposite and one sides of the substrate to inject holes and electrons, and are applied to any one of an illumination system and a display system. The method of claim 8, wherein the resonator, A first reflecting film formed on the opposite side of the substrate; And a second reflecting film formed on the doped region to form a resonator with the first reflecting film to improve light emission wavelength selectivity, wherein one of the first and second reflecting films has a lower reflectance than the other reflecting film. And emitting light emitted through one reflective film having a low reflectance. The device of claim 9, wherein the second reflective film is a Bragg reflective film formed by alternately stacking materials having different refractive indices. The light emitting device according to claim 9 or 10, wherein the first reflective film is formed on an opposite surface of the substrate, and the first electrode is formed on an opposite surface of the substrate around the first reflective film. Device. The device of claim 9 or 10, wherein the first electrode is formed of a transparent electrode between an opposite surface of the substrate and the first reflective film. The method according to claim 8 or 9, And a control film which functions as a mask when forming the doped region on one surface of the substrate and allows the doped region to be formed with an extremely shallow doping depth. The method of claim 13, wherein the substrate is made of a predetermined semiconductor material including silicon, And the control film is a silicon oxide film having an appropriate thickness such that the first and second doped regions are formed with an extremely shallow doping depth.