CN118053888A - Multi-chip addressable LED - Google Patents

Abstract

The application provides a multi-chip addressable LED, which is characterized by comprising: the LED driving device comprises a control driving chip, at least two LED chips and switches corresponding to the LED chips one by one; the switch is electrically connected with the control driving chip and is used for being turned on or turned off according to a control signal output by the control driving chip; the LED chip and the switch are positioned on the same epitaxial layer, and through the design, the problem of low control signal efficiency of the LED can be solved, the integration level of the chip is improved, and the reliability of the chip is improved.

Description

Multi-chip addressable LED

Technical Field

The invention relates to the technical field of lasers, in particular to a multi-chip addressable LED.

Background

An LED, namely a light-emitting diode, is a semiconductor solid light-emitting device, which uses an InGaN/GaN MQW quantum well as a light-emitting source, and generates carrier recombination in the quantum well under forward bias voltage to release energy and emit photons, and directly emits red, yellow, blue, green, cyan, orange and purple light. At present, a white light LED is mainly made by covering a yellowish fluorescent powder coating on a blue light LED. The semiconductor light-emitting diode LED has the advantages of high luminous efficiency, long service life, environmental protection, high switching speed and the like, and is widely applied to various fields of indication, display, decoration, backlight source, urban landscape illumination and the like as a new generation of green illumination light source.

HEMTs are semiconductor materials with different forbidden bandwidths at two sides of a heterojunction, and the fermi energy levels are different, so that electrons are transferred from a wide forbidden band to a narrow forbidden band until the fermi energy levels are the same. Therefore, the surplus holes are reserved on the wide forbidden band side, the surplus electrons are reserved on the narrow forbidden band side, the energy bands of the surplus holes and electrons are bent due to a built-in electric field generated at the heterojunction interface, a triangular potential well is generated, and two-dimensional electron gas is accumulated in the potential well. The larger the difference of the forbidden bandwidths of the two materials is, the stronger the built-in electric field is, the deeper the generated triangle potential well is, and the higher the two-dimensional electron gas concentration is. For depletion HEMTs, the grid electrode has enough two-dimensional electron gas concentration when no voltage is applied, negative pressure is applied to the grid electrode when the grid electrode is turned on, an electric field opposite to a built-in electric field is generated when the grid electrode is turned off, interface energy band bending is relieved, the depth of a triangle potential well is reduced, and therefore the two-dimensional electron gas concentration is reduced. For the enhanced HEMT, when the grid is not applied with voltage, the grid electrode schottky barrier effect or the doping concentration of the barrier layer is too low, the two-dimensional electron gas concentration is very low, the conduction cannot be realized, positive pressure is applied to the grid electrode when the grid is started, an electric field in the same direction as the built-in electric field is generated, the energy band bending is increased, the depth of a triangle potential well is increased, and therefore the two-dimensional electron gas concentration is increased, and the HEMT is conducted.

Gallium nitride high electron mobility transistor GaN HEMT (High Electron MobilityTransistors) is representative of Wide Bandgap (WBG) power semiconductor devices, which have great potential for high frequency power applications. GaN materials have higher electron mobility than Si and SiC.

The addressable LEDs of the prior art are typically controlled by controlling the LEDs with individually addressable (and individually controllable) light sources via a network, which requires a number of individual control signals to control each of these individual light sources. Resulting in a large amount of network traffic and thus possibly having a strong impact on the utilization of the (wireless) network. Furthermore, the system architecture of a networked lighting system may not support a large number of control signals during a particular period of time. Therefore, a new addressable LED structure is needed to solve the technical problem of low control signal efficiency in the addressable LED.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provide a multi-chip addressable LED so as to solve the problems of low signal-producing efficiency of the LED and the integration level of the LED chips in the related art, and the problem that the inter-chip interconnection length is increased to influence the reliability of the chips.

In order to achieve the above purpose, the technical scheme adopted by the embodiment of the invention is as follows:

an embodiment of the present invention provides a multi-chip addressable LED, which is characterized by comprising: the LED driving device comprises a control driving chip, at least two LED chips and switches corresponding to the LED chips one by one; the switch is electrically connected with the control driving chip and is used for being turned on or turned off according to a control signal output by the control driving chip; the LED chip and the switch are positioned on the same epitaxial layer.

Optionally, the switch is a GaN HEMT.

Optionally, a GaN-LED epitaxy, an AlGaN etching stop layer and a GaN-HEMT epitaxy are sequentially grown on the epitaxy.

Optionally, source, drain, gate electrode ohmic contacts are formed.

Optionally, two mesas are formed in the photolithographic LED area, the P-GaN layer and the N-GaN layer are exposed respectively, the current spreading layer ITO is prepared and the LED electrodes are electroplated.

Optionally, the N electrode of the LED is electrically connected to the Drain electrode of the HEMT.

Optionally, the LED area is photoetched to expose the N-GaN layer table top, a current expansion layer ITO is prepared on the P-GaN layer, and an LED electrode is electroplated.

Optionally, the P electrode of the LED is electrically connected to the Drain electrode of the HEMT.

Optionally, one HEMT device controls the plurality of LEDs to emit light.

The beneficial effects of the invention are as follows:

The invention provides a multi-chip addressable LED, which is characterized by comprising: the LED driving device comprises a control driving chip, at least two LED chips and switches corresponding to the LED chips one by one; the switch is electrically connected with the control driving chip and is used for being turned on or turned off according to a control signal output by the control driving chip; the LED chip and the switch are positioned on the same epitaxial layer, and through the design, the problem of low control signal efficiency of the LED can be solved, the integration level of the chip is improved, and the reliability of the chip is improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a schematic diagram of an addressable LED system as provided in the prior art;

FIG. 2 is a schematic diagram of another addressable LED system according to an embodiment of the present application;

Fig. 3 is a schematic diagram of an epitaxial structure of an LED chip according to the prior art;

fig. 4 is a schematic diagram of an epitaxial structure of a HEMT chip provided in the prior art;

Fig. 5 is a schematic diagram of a device structure of an LED chip and a HEMT switch provided in an embodiment of the present application on the same epitaxy;

fig. 6 is a schematic diagram of a device interconnection manner of an LED chip and a HEMT switch on the same epitaxy provided in an embodiment of the present application;

fig. 7 is a schematic diagram of an interconnection manner of another LED chip and a HEMT switch on the same epitaxy device provided in an embodiment of the present application.

Detailed Description

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention.

Fig. 1 is a schematic diagram of an addressable LED system as provided in the prior art. The addressable LED system 10 as shown in fig. 1 comprises at least two LED chips 101 and switches 102 in one-to-one correspondence with the LED chips and a control driving chip 103. The switch 102 is electrically connected with the control driving chip 103, the circuit switch 102 is used for being turned on or off according to a control signal output by the control driving chip 103, the LED chips 101 are respectively electrically connected with the switch 102, and when the switch 102 is turned on, the LED chips 101 connected with the turned-on switch 102 emit light. The control driving chip 103 can independently control the plurality of switches 102. The switches 102 in series on the circuits of the different LED chips 101 may use GaN HEMTs or other switches, the laser chips 101 may include gallium arsenide (GaAs) or/and aluminum arsenide (AlGaAs) multiple quantum well structures, or indium phosphide (InP-based) materials, and the wavelength of the VCSEL chips 101 may be 850nm, 940nm, 1350nm, or set as desired. The control driving chip 103 controls at least two LED chips to sequentially emit light according to actual needs, so that the duty ratio of the working state of the LED chips is reduced, heat accumulation is reduced, the working efficiency is improved, and the heat dissipation difficulty is reduced.

If the LED chip and the switch are integrated on the same circuit board independently of each other, the integration level of the chip is reduced, and the interconnection length is increased, so that the reliability of the chip is affected.

Fig. 2 is a schematic diagram of another addressable LED system according to an embodiment of the present application. As shown in fig. 2, the LED chip and the power switch are prepared on the same epitaxy, and the gold wires are used for connection, so that the chip area is reduced, the chip integration level is improved, the number of gold wires and pads is reduced, and the complexity of the driving circuit is reduced.

Fig. 3 is a schematic diagram of an epitaxial structure of an LED chip according to the prior art. The LED chip epitaxial structure shown in fig. 3 includes a 1.gan buffer layer, a 2.undoped GaN layer, a 3.doped n-GaN layer, a 4.ingan/GaN Multiple Quantum Well (MQW) active layer, a 5.mg doped p-AlGaN layer, and a 6.mg doped p-GaN layer grown sequentially on a Sapphire substrate (Sapphire-sub) disposed sequentially from bottom to top.

Fig. 4 is a schematic diagram of an epitaxial structure of a HEMT chip provided in the prior art. The epitaxial structure of the HEMT chip shown in fig. 4 includes a nucleation layer 1.Aln, a 2.Alxga1-xN graded layer, a 3. Undoped GaN buffer layer, a 4.GaN channel layer, a 5.Aln isolation layer, a 6.Algan barrier layer, and a 7.GaN cap layer grown sequentially on a Sapphire substrate (Sapphire-sub) that is sequentially disposed from bottom to top.

Fig. 5 is a schematic diagram of a device structure of an LED chip and a HEMT switch on the same epitaxy according to an embodiment of the present application. The integrated epitaxial structure as shown in fig. 5 includes a grown LED epitaxy and a grown HEMT epitaxy. LED epitaxy: and a 1.GaN buffer layer, a 2. Doped n-GaN layer, a 3.InGaN/GaN Multiple Quantum Well (MQW) active layer, a 4.Mg doped p-AlGaN layer and a 5.Mg doped p-GaN cap layer are sequentially grown on the sapphire substrate. And continuing to grow an AlGaN etching stop layer, and growing HEMT epitaxy on the AlGaN etching stop layer, wherein the HEMT epitaxy is sequentially an undoped GaN buffer layer, a GaN channel layer, an AlN isolation layer, an AlGaN barrier layer and a GaN cap layer.

Fig. 6 is a schematic diagram of a device interconnection manner of an LED chip and a HEMT switch on the same epitaxy according to an embodiment of the present application. As shown in fig. 6, the LED chip and the HEMT switch are on the same epitaxial layer, so that the integration level and reliability of the chip can be improved. Unlike GaAs-based semiconductors, p-GaN tends to have a large bulk resistance, and in order to allow current to be injected uniformly to limit the aperture, a current spreading structure must be provided on the pGaN surface. The process of forming the device shown in fig. 6 includes the steps of:

(1) Growing GaN-LED epitaxy, alGaN etching stop layer and GaN-HEMT on substrate in turn

Epitaxy;

(2) Photoetching, metal deposition, metal stripping and high-temperature rapid thermal annealing to form source, drain and gate electrode ohmic contacts;

(3) Photoetching an LED region to form two table tops, respectively exposing the P-GaN layer and the N-GaN layer, preparing a current expansion layer ITO and electroplating an LED electrode;

(4) And (5) metal interconnection. To prevent shorting of the two devices, a passivation layer is deposited and then the N electrode of the LED is interconnected with the Drain electrode of the HEMT.

Fig. 7 is a schematic diagram of an interconnection manner of another LED chip and a HEMT switch on the same epitaxy device provided in an embodiment of the present application. As shown in fig. 7, the LED chip and the HEMT switch are on the same epitaxial layer, so that the integration level and reliability of the chip can be improved. Unlike GaAs-based semiconductors, p-GaN tends to have a large bulk resistance, and in order to allow current to be injected uniformly to limit the aperture, a current spreading structure must be provided on the pGaN surface. The process of forming the device shown in fig. 7 includes the steps of:

(1) Growing GaN-LED epitaxy, alGaN etching stop layer and GaN-HEMT on substrate in turn

Epitaxy;

(2) Photoetching, metal deposition, metal stripping and high-temperature rapid thermal annealing to form source, drain and gate electrode ohmic contacts;

(3) Photoetching an LED area to expose the N-GaN layer table top, preparing a current expansion layer ITO on the P-GaN layer, and electroplating an LED electrode;

(4) And (5) metal interconnection. In order to prevent the short circuit of two devices and the complete coverage of metal wires and connection of the two electrodes, a passivation layer is deposited to serve as an isolation region between the devices, and then the P electrode of the LED is interconnected with the Drain electrode of the HEMT.

Based on the integrated structure shown in fig. 7, an addressable integrated device in which one HEMT device controls the light emission of a plurality of LEDs can be prepared.

It should be noted that in this document, relational terms such as "first" and "second" and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

The above description is only of the preferred embodiments of the present application and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application. It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further definition or explanation thereof is necessary in the following figures. The above description is only of the preferred embodiments of the present application and is not intended to limit the present application, but various modifications and variations can be made to the present application by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims (9)

1. A multi-chip addressable LED comprising: the LED driving device comprises a control driving chip, at least two LED chips and switches corresponding to the LED chips one by one; the switch is electrically connected with the control driving chip and is used for being turned on or turned off according to a control signal output by the control driving chip; the LED chip and the switch are positioned on the same epitaxial layer.

2. The multi-chip addressable LED of claim 1, wherein the switch is a GaN HEMT.

3. The multi-chip addressable LED of claim 1, wherein a GaN-LED epitaxy, an AlGaN etch stop layer, and a GaN-HEMT epitaxy are grown sequentially on the epitaxy.

4. A multi-chip addressable LED according to claim 3, wherein source, drain, gate electrode ohmic contacts are formed.

5. The multi-chip addressable LED of claim 4, wherein the photolithographic LED area forms two mesas exposing the P-GaN layer and the N-GaN layer, respectively, preparing the current spreading layer ITO and plating the LED electrodes.

6. The multi-chip addressable LED of claim 5, wherein the N electrode of the LED is electrically connected to the Drain electrode of the HEMT.

7. The multi-chip addressable LED of claim 4, wherein the photolithographic LED area exposes an N-GaN layer mesa, a current spreading layer ITO is fabricated on the P-GaN layer and the LED electrodes are electroplated.

8. The multi-chip addressable LED of claim 7, wherein the P-electrode of the LED is electrically connected to the Drain electrode of the HEMT.

9. The multi-chip addressable LED of claim 8, wherein one HEMT device controls the emission of multiple LEDs.