CN217086610U

CN217086610U - LED structure

Info

Publication number: CN217086610U
Application number: CN202123217328.3U
Authority: CN
Inventors: 刘慰华
Original assignee: Wuxi Jingzhan Semiconductor Co ltd
Current assignee: Wuxi Jingzhan Semiconductor Co ltd
Priority date: 2021-12-20
Filing date: 2021-12-20
Publication date: 2022-07-29
Anticipated expiration: 2031-12-20

Abstract

The utility model discloses a LED structure, including the substrate to and stack gradually the first semiconductor layer, quantum well structure and the second semiconductor layer that set up on the substrate, the quantum well structure includes at least one deck quantum well layer, and the quantum well layer includes the potential well layer that is close to substrate one side, keeps away from the barrier layer of substrate one side and sets up the stress modulation structure between potential well layer and barrier layer; the stress modulation structure prevents In elements In the potential well layer from separating and escaping on one hand, effectively improves the crystal quality of the potential well layer, and on the other hand, built-In stress exists between the stress modulation structure and the structure below the stress modulation structure, so that two-dimensional expansion of carriers can be realized when the carriers are injected into the lower surface of the stress modulation structure under the condition of externally applied electric field, the radiation recombination efficiency of the carriers In the potential well layer is further improved, and the internal quantum efficiency of the LED structure is improved.

Description

LED structure

Technical Field

The present disclosure relates to the field of technology, and more particularly, to an LED structure.

Background

When a GaN-based LED structural material is prepared based on the traditional MOCVD epitaxy, the quality of the upper surface of a crystal of a potential well (QW) material InGaN rear crystal in an epitaxial active region stage is poor, the defect density is increased, the quality of a subsequent material is influenced, and in the electroluminescence process, the increased defects form a non-radiative recombination center with more carriers, so that the internal quantum efficiency of the whole LED structure is influenced. In the LED structure with the potential well layer (31) with high In component (In ratio is more than 30%), the GaN-based LED structure prepared by the traditional technical scheme has serious influence because the defect density is sharply increased.

The prior solution improves the quality of the corresponding epitaxial material by increasing the epitaxial temperature or increasing the hydrogen ratio In the epitaxial atmosphere gas after completing the InGaN epitaxy of the potential well material so as to solve the technical problem, and the solution has good effect In the LED structure of the potential well layer (31) with lower In component ratio; however, In the LED structure having the well layer (31) with a higher In component ratio, the In element In the InGaN material of the well layer (31) is separated and escaped and the In component is reduced by raising the epitaxial temperature or increasing the hydrogen gas content In the epitaxial atmosphere, so that the original high In component material In the well layer (31) is damaged.

SUMMERY OF THE UTILITY MODEL

The present disclosure provides an LED structure to improve the internal quantum efficiency of the LED structure and prevent In components In a potential well layer from escaping to affect the crystal quality.

The present disclosure provides an LED structure, comprising:

a substrate, and a first semiconductor layer, a quantum well structure and a second semiconductor layer which are sequentially stacked on the substrate,

the quantum well structure comprises at least one quantum well layer, wherein the quantum well layer comprises a potential well layer close to one side of the substrate, a barrier layer far away from one side of the substrate and a stress modulation structure arranged between the potential well layer and the barrier layer.

Further, the material of the stress modulation structure is a group iii-v compound material, and the stress modulation structure includes an Al component that gradually increases in a direction from the substrate toward the second semiconductor layer.

Further, the quantum well structure comprises a plurality of quantum well layers, the stress modulation structure comprises Al components, and in the direction pointing to the second semiconductor layer from the substrate, the Al components of the stress modulation structures of different quantum well layers are increased layer by layer, and/or the thicknesses of the stress modulation structures of different quantum well layers are increased layer by layer.

Furthermore, the stress modulation structure comprises a transition layer and a stress modulation layer which are arranged in a stacked mode.

Furthermore, the material of the transition layer is a gallium nitride-based material.

Further, the thickness of the transition layer is less than 3 nm.

Further, the stress modulation layer is made of III-V compound material.

Further, the thickness of the stress modulation layer is less than 2 nm.

Further, the transition layer and/or the stress modulation layer are undoped layers or N-type doped layers.

Furthermore, the doping concentration of the N-type doping layer is less than 1 × 10 ¹⁸ cm ^-3 。

Further, the LED structure further comprises a first electrode and a second electrode, wherein the first electrode is electrically connected with the first semiconductor layer, and the second electrode is electrically connected with the second semiconductor layer.

According to the stress modulation structure arranged between the potential well layer and the barrier layer In the quantum well layer of the LED structure, on one hand, In element In the potential well layer is prevented from being separated and escaping, the crystal quality of the potential well layer is effectively improved, on the other hand, built-In stress exists between the stress modulation structure and the lower structure, so that two-dimensional expansion of carriers is facilitated when the carriers are injected into the lower surface of the stress modulation structure under the condition that an electric field is applied externally, the radiation recombination efficiency of the carriers In the potential well layer is further improved, and the internal quantum efficiency of the LED structure is improved.

Drawings

Fig. 1-2 are schematic cross-sectional views of a first embodiment of an LED structure according to the present disclosure;

FIG. 3 is a schematic cross-sectional view of a second embodiment of an LED structure of the present disclosure;

FIG. 4 is a schematic cross-sectional view of a third embodiment of an LED structure of the present disclosure;

fig. 5 is a schematic cross-sectional view of a fourth embodiment of an LED structure of the present disclosure.

Description of reference numerals: 1-substrate, 2-first semiconductor layer, 3-quantum well layer, 31-potential well layer, 32-stress modulation structure, 321-transition layer, 322-stress modulation layer, 33-barrier layer, 4-second semiconductor layer, 5-first electrode, 6-second electrode, 7-nucleation layer and 8-buffer layer.

Detailed Description

Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. When the following description refers to the accompanying drawings, like numbers in different drawings represent the same or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present disclosure. Rather, they are merely examples of devices consistent with certain aspects of the present disclosure, as detailed in the appended claims.

The terminology used in the present disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. Unless otherwise defined, technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure belongs. The use of "first," "second," and similar terms in the description and claims does not indicate any order, quantity, or importance, but rather is used to distinguish one element from another. Also, the use of the terms "a" or "an" and the like do not denote a limitation of quantity, but rather denote the presence of at least one. "plurality" or "a number" means two or more. Unless otherwise indicated, "front", "rear", "lower" and/or "upper" and the like are for convenience of description and are not limited to one position or one spatial orientation. The word "comprising" or "comprises", and the like, means that the element or item listed as preceding "comprising" or "includes" covers the element or item listed as following "comprising" or "includes" and its equivalents, and does not exclude other elements or items. The terms "connected" or "coupled" and the like are not restricted to physical or mechanical connections, but may include electrical connections, whether direct or indirect. As used in this disclosure and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should also be understood that the term "and/or" as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items.

Example one

Fig. 1 and fig. 2 are schematic cross-sectional views of a first embodiment of the present disclosure, which provides an LED structure, including:

the semiconductor device comprises a substrate (1), and a first semiconductor layer (2), a quantum well structure and a second semiconductor layer (4) which are sequentially stacked on the substrate (1), wherein the quantum well structure comprises at least one quantum well layer (3), the quantum well layer (3) comprises a potential well layer (31) close to one side of the substrate (1), a barrier layer (33) far away from one side of the substrate (1) and a stress modulation structure (32) arranged between the potential well layer (31) and the barrier layer (33).

The well layer (31) comprises an In element, the stress modulation structure (32) is arranged between the well layer (31) and the barrier layer (33) In the quantum well layer (3), on one hand, the In element In the well layer (31) is prevented from separating and escaping, the crystal quality of the well layer (31) is effectively improved, on the other hand, built-In stress exists between the stress modulation structure (3) and the lower structure, so that two-dimensional expansion of carriers is facilitated when the carriers are injected into the lower surface of the stress modulation structure (32) under the condition of externally applied electric field, the radiation recombination efficiency of the carriers In the well layer (31) is further improved, and the internal quantum efficiency of the LED structure is improved.

The first semiconductor layer (2) and the second semiconductor layer (4) are opposite in conductivity type, preferably, the first semiconductor layer (2) is an N-type doped semiconductor layer, and the second semiconductor layer (4) is a P-type doped semiconductor layer; the material of the first semiconductor layer (2) and the second semiconductor layer (4) may be a GaN-based material, and in this embodiment, the material of the first semiconductor layer (2) and the second semiconductor layer (4) is preferably GaN, which is not limited herein.

In this embodiment, the well layer (31) and the barrier layer (33) are both GaN-based materials, wherein the well layer includes In element, preferably, the well layer (31) is InGaN, and the barrier layer is GaN.

Further, the material of the stress modulation structure (32) is a III-V compound material, and the stress modulation structure (32) comprises an Al component which gradually rises in a direction from the substrate (1) to the second semiconductor layer (4).

In the embodiment, the stress modulation structure (32) is preferably made of single-layer Al with gradually changed Al component _x Ga _1-x N material, wherein Al is present in the direction from the substrate (1) to the second semiconductor layer (4) _x Ga _1-x The Al component in N gradually increases. Specifically, x is 0. ltoreq. x.ltoreq.1, and the value of x gradually increases from 0 to 1 in a direction from the substrate (1) toward the second semiconductor layer (4).

Further, the way of gradually increasing the Al composition in the stress modulation structure (32) may be a linear increase, a stepwise increase, or a combination of the two increasing ways, which is not limited in this embodiment.

When the LED structure is grown by the traditional MOCVD, the epitaxial layer with high Al component and the barrier layer (33) usually need to be set at higher temperature, while the potential well layer (31) containing In element is correspondingly set at lower epitaxial temperature, so that the stress modulation structure (32) with gradually changed Al components is arranged to effectively play a role In buffering transition, the crystal quality of the potential well layer (31) can be effectively improved, and the phenomenon that the In element In the potential well layer (31) is separated and escaped to cause damage by sudden high-temperature epitaxy is avoided.

The material of the substrate (1) can be selected from Si, Al ₂ O ₃ One or more combinations selected from materials such as SiC and GaN, and the like, and a nucleating layer (7) and a buffer layer (8) can be sequentially arranged between the substrate (1) and the first semiconductor layer (2) so as to improve the crystal quality of an epitaxial structure above the heterogeneous substrate and reduce defects.

Example two

As shown in fig. 3, fig. 3 is a schematic cross-sectional view of a second embodiment of the LED structure of the present disclosure. The main structure of the second embodiment is substantially the same as that of the first embodiment, and only the difference portion is described below, and the description of the same portion is omitted.

In the present embodiment, the quantum well structure is a multiple quantum well layer (3) structure, and the quantum well structure includes a plurality of quantum well layers (3) arranged in a stacked manner.

Preferably, the Al composition of the stress modulation structure (32) of each of the multilayer laminated quantum well layers (3) increases layer by layer in a direction from the substrate (1) to the second semiconductor layer (4).

Further, the Al component of the stress modulation structure (32) of each quantum well layer (3) increases layer by layer in the direction from the substrate (1) to the second semiconductor layer (4) by the following way:

the Al component of the stress modulation structures (32) of the quantum well layers (3) increases layer by layer in the direction from the substrate (1) to the second semiconductor layer (4), and/or the thickness of the stress modulation structures (32) of the quantum well layers (3) increases layer by layer in the direction from the substrate (1) to the second semiconductor layer (4).

Preferably, the thickness of the stress modulation structure (32) of each quantum well layer (3) is less than 5nm, and the thickness of the stress modulation structure (32) of each quantum well layer (3) in the embodiment is preferably 2 nm-5 nm.

The arrangement of the multi-quantum well layer (3) structure enables the energy band in the potential well layer (31) of the quantum well structure to tend to be quantized more, and the locality is better; and the recombination probability of the carriers in the potential well layer (31) can be improved, so that the recombination energy gap size of the carriers in the potential well layer (31) tends to be consistent.

EXAMPLE III

Fig. 4 is a schematic cross-sectional view of a third embodiment of an LED structure according to the present disclosure. The third embodiment has basically the same main structure as the first and second embodiments, and the difference is that:

the stress modulation structure (32) includes a transition layer (321) and a stress modulation layer (322) which are stacked.

Furthermore, the material of the transition layer (321) is a gallium nitride-based material, and in the embodiment, the transition layer (321) is preferably a GaN single layer.

Furthermore, the thickness of the transition layer (321) is less than 3nm, and in the embodiment, the thickness of the transition layer is preferably between 1nm and 3 nm.

Furthermore, the material of the stress modulation layer (322) is III-V compound material, and the stress modulation layer (322) is preferably AlN single layer in this embodiment.

Furthermore, the thickness of the stress modulation layer (322) is less than 2nm, and in the embodiment, the thickness of the stress modulation layer is preferably between 1nm and 2 nm. When the quantum well structure is a plurality of quantum well layers (3), the thickness of the stress modulation layer (322) of each quantum well layer (3) increases layer by layer in the direction from the substrate (1) to the second semiconductor layer (4).

Built-in stress is caused by the difference of material lattice constants between the stress modulation layer (322) and the transition layer (321) and the well layer (31) below the stress modulation layer, so that the lower surface of the stress modulation layer (322) is under the condition of an applied electric field, and the transverse/two-dimensional expansion is more favorably realized when carriers are injected to the lower surface of the stress modulation layer (322), the efficiency of completing radiation recombination of the carriers in the well layer (31) is improved, and the internal quantum efficiency of the LED structure is improved.

The stress modulation layer (322) has another function that the stress modulation layer (322) is arranged to realize effective isolation protection function, effectively avoid In element separation and escape In the quantum well layer (31), and improve the crystal quality of the potential well layer (31).

The traditional MOCVD needs to set a higher temperature when growing the AlN material, and the quantum well layer (31) needs to set a lower growth temperature, so the transition layer (321) can realize an effective buffer effect.

Further, the transition layer (321) and/or the stress modulation layer (322) are undoped layers or N-type doped layers, and preferably, when the transition layer (321) and/or the stress modulation layer (322) are N-type doped layers, the doping concentration of the transition layer (321) and the stress modulation layer (322) is less than 1 × 10 ¹⁸ cm ^-3 . The transition layer (321) and/or the stress modulation layer (322) are/is N-type doped layers, so that the driving voltage of the LED structure can be effectively reduced.

Example four

Fig. 5 is a schematic cross-sectional view of a fourth embodiment of an LED structure of the present disclosure. The technical solution of the fourth embodiment is basically the same as the technical solutions of the first embodiment, the second embodiment and the third embodiment in main structure, only the difference portions are described below, and the description of the same portions is omitted.

Further, the LED structure further comprises a first electrode (5) and a second electrode (6), wherein the first electrode (5) is electrically connected with the first semiconductor layer (2), and the second electrode (6) is electrically connected with the second semiconductor layer (4).

The second electrode (6) is arranged on the second semiconductor layer (4), and the first electrode (5) is arranged on the surface of the substrate (1) far away from the first semiconductor layer (2); the first electrode (5) is a cathode and the second electrode (6) is an anode.

Although the present disclosure has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the disclosure.

Claims

1. An LED structure, comprising:

a substrate (1), and a first semiconductor layer (2), a quantum well structure and a second semiconductor layer (4) which are sequentially stacked on the substrate (1),

the quantum well structure comprises at least one quantum well layer (3), wherein the at least one quantum well layer (3) comprises a potential well layer (31) close to one side of the substrate (1), a barrier layer (33) far away from one side of the substrate (1) and a stress modulation structure (32) arranged between the potential well layer (31) and the barrier layer (33).

2. The LED structure of claim 1, wherein the stress modulating structure (32) is a iii-v compound material.

3. LED structure according to claim 1, characterized in that the quantum well structure comprises a plurality of quantum well layers (3), the thickness of the stress modulating structure (32) of different quantum well layers (3) increasing layer by layer in a direction pointing from the substrate (1) to the second semiconductor layer (4).

4. The LED structure according to any of claims 1 to 3, wherein the stress modulation structure (32) comprises a transition layer (321) and a stress modulation layer (322) arranged in a stack.

5. The LED structure according to claim 4, wherein the material of the transition layer (321) is a gallium nitride based material.

6. The LED structure according to claim 4, wherein the thickness of the transition layer (321) is less than 3 nm.

7. The LED structure of claim 4, wherein the stress modulation layer (322) is a iii-v compound material.

8. The LED structure of claim 4, wherein said stress modulation layer (322) has a thickness of less than 2 nm.

9. LED structure according to claim 4, characterized in that the transition layer (321) and/or the stress modulation layer (322) is an undoped or N-doped layer.

10. LED structure according to claim 1, characterized in that the LED structure further comprises a first electrode (5) and a second electrode (6), the first electrode (5) being electrically connected with the first semiconductor layer (2), the second electrode (6) being electrically connected with the second semiconductor layer (4).