阅读说明：本技术 一种氮化镓基谐振腔发光二极管及其制备方法 (Gallium nitride-based resonant cavity light-emitting diode and preparation method thereof ) 是由 张保平 徐欢 梅洋 杨帅 应磊莹 侯想 罗荣煌 卢文瑞 陈锋 钟梦洁 刘熠新 于 2021-06-22 设计创作，主要内容包括：本发明公开了一种氮化镓基谐振腔发光二极管及其制备方法,氮化镓基谐振腔发光二极管包括依序层叠设置的支撑基板、高对比度光栅、有源区、N型层,N型层远离有源区的端面上还设置有第一反射镜和N电极；其中,高对比度光栅由P型层和透明导电层组成,P型层的一端面与有源区贴合,P型层的另一端面上经刻蚀形成非平整的光栅结构,透明导电层设置在P型层的光栅结构间隙和表面；本方案直接使用部分P型层及透明导电层作为高对比度光栅结构以替代传统的底部反射镜结构,不仅减小了器件串联电阻,降低吸收损耗,还提高了输出光质量,且制备工艺简单,所有制备工艺与标准半导体制备工艺兼容,满足大规模光电集成的需要。(The invention discloses a gallium nitride-based resonant cavity light-emitting diode and a preparation method thereof, wherein the gallium nitride-based resonant cavity light-emitting diode comprises a support substrate, a high-contrast grating, an active region and an N-type layer which are sequentially stacked, wherein a first reflector and an N electrode are further arranged on the end surface of the N-type layer far away from the active region; the high-contrast grating consists of a P-type layer and a transparent conducting layer, wherein one end face of the P-type layer is attached to the active region, the other end face of the P-type layer is etched to form an uneven grating structure, and the transparent conducting layer is arranged in the gap and the surface of the grating structure of the P-type layer; according to the scheme, part of the P-type layer and the transparent conducting layer are directly used as a high-contrast grating structure to replace a traditional bottom reflector structure, so that the series resistance of devices is reduced, the absorption loss is reduced, the output light quality is improved, the preparation process is simple, all the preparation processes are compatible with a standard semiconductor preparation process, and the requirement of large-scale photoelectric integration is met.)

1. A gallium nitride-based resonant cavity light-emitting diode is characterized by comprising a supporting substrate, a high-contrast grating, an active region and an N-type layer which are sequentially stacked, wherein a first reflector and an N electrode are further arranged on the end face, far away from the active region, of the N-type layer;

the high-contrast grating is composed of a P-type layer and a transparent conducting layer, one end face of the P-type layer is attached to the active area, the other end face of the P-type layer is etched to form an uneven grating structure, and the transparent conducting layer is arranged in gaps and on the surface of the grating structure of the P-type layer.

2. The gan-based resonant cavity light emitting diode of claim 1, wherein the P-type layer is a patterned etched grating structure and the high-contrast grating is configured to act as a second mirror to provide optical confinement;

wherein the refractive index of the P type layer is larger than that of the transparent conductive layer.

3. The gan-based resonant cavity led of claim 2, wherein the cross-section of the grating structure formed by the patterned etching of the P-type layer is stripe, mesh or column.

4. The gallium nitride-based resonant cavity light emitting diode of claim 1, wherein the contact between the transparent conductive layer and the P-type layer is an ohmic contact.

5. The gan-based resonant cavity light emitting diode of claim 1, wherein the supporting substrate is formed of a hard material.

6. The GaN-based resonant cavity light-emitting diode of one of claims 1 to 5, wherein the first mirror is a dielectric film DBR or metal mirror or HCG structure, and the reflectivity of the first mirror is less than that of the high-contrast grating.

7. The GaN-based resonant cavity light-emitting diode of claim 6, wherein the supporting substrate is formed of a metal or ceramic material, and the N electrode is formed of Cr, Au, Ni, Au, Ti or Au material.

8. A preparation method of a gallium nitride-based resonant cavity light-emitting diode is characterized by comprising the following steps:

s1, growing a semiconductor epitaxial layer of a pin structure on the original substrate;

s2, etching p-GaN on the outer surface of the semiconductor epitaxial layer to form an HCG structure, and preparing a blank A;

s3, depositing a transparent conducting layer on the upper surface of the blank A to obtain a blank B;

s4, preparing a support substrate on the upper surface of the blank B to obtain a blank C;

s5, inverting the blank C, and then removing the original substrate to expose the end face of the semiconductor epitaxial layer far away from the support substrate;

s6, preparing an N electrode on the end face of the semiconductor epitaxial layer far away from the supporting substrate;

and S7, preparing a first reflector on the end face of the semiconductor epitaxial layer far away from the supporting substrate, and finishing the manufacture of the device.

9. The method according to claim 8, wherein step S1 is a semiconductor epitaxial layer with a pin structure grown by MOCVD or MBE;

the semiconductor epitaxial layer comprises an N-type layer, an active region and a P-type layer which are sequentially stacked on an original substrate;

the supporting substrate is formed by metal or ceramic materials and is prepared by electroplating, deposition or metal bonding.

10. A vertical cavity surface emitting laser comprising the gallium nitride based resonant cavity light emitting diode according to any one of claims 1 to 7.

Technical Field

The invention relates to the technical field of semiconductor light emitting, in particular to a gallium nitride-based resonant cavity light emitting diode and a preparation method thereof, which are suitable for semiconductor resonant cavity devices with various wavelengths (visible light wave bands and ultraviolet light wave bands), and comprise a vertical cavity surface emitting laser and a resonant cavity light emitting diode.

Background

A semiconductor Resonant Cavity Light Emitting Diode (RCLED) has a wide application field including semiconductor illumination, backlight display, biomedical, optical communication, and the like. The structure is a top mirror and a bottom mirror for optical feedback, and an active region sandwiched therebetween for providing outgoing photons. The high-reflectivity broadband cavity mirror is a necessary condition for constructing a high-quality factor resonant cavity device. The bottom mirror typically employs a Distributed Bragg Reflector (DBR) or a metal mirror. DBRs are composed of multiple layers of alternating dielectric materials with a periodic change in refractive index, their reflectivity and bandwidth depending on the refractive index contrast of the constituent materials and the thickness of each layer, both nitride DBRs and dielectric film DBRs being common. There is a small difference in refractive index between the constituent materials of the nitride DBR, and thus it is generally necessary to stack a considerable number of DBR pairs to obtain a sufficiently high reflectivity, which leads to difficulty in epitaxial growth; the dielectric film DBR has poor electrical and thermal characteristics, which greatly affects the electrical performance of the device and limits the maximum output power of the device. The metal mirror has better electrical and thermal properties, but is difficult to achieve high reflectivity and has higher absorption.

Compared with the reflectors of the above types, the High Contrast Grating (HCG) reflector has the advantages of few film layers, High diffraction efficiency, large bandwidth, good polarization, large manufacturing tolerance and the like, and meanwhile, the required materials have wide sources and simple process, and the consumption is less than 10% of the materials used by the DBR. The grating with sub-wavelength size is usually prepared by growing high-refractive-index material on low-refractive-index material (oxide or air), etching the high-refractive-index material layer to form the grating, and changing the grating parameters to obtain high reflectivity from visible light to infrared band. However, few reports are reported in the current literature on the use of HCG structures for bottom mirrors, and therefore the technology proposed by the present invention creatively uses HCG as a bottom mirror, overcoming other cavity mirror limitations while providing additional performance advantages.

Disclosure of Invention

In view of this, the present invention provides a gallium nitride-based resonant cavity light emitting diode with good optical performance and reliable and simple preparation method.

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

a gallium nitride-based resonant cavity light-emitting diode comprises a supporting substrate, a high-contrast grating, an active region and an N-type layer which are sequentially stacked, wherein a first reflector and an N electrode are further arranged on the end face, far away from the active region, of the N-type layer;

the high-contrast grating is composed of a P-type layer and a transparent conducting layer, one end face of the P-type layer is attached to the active area, the other end face of the P-type layer is etched to form an uneven grating structure, the transparent conducting layer is arranged in gaps and on the surface of the grating structure of the P-type layer, namely the portion, attached to the active area, of the P-type layer serves as a normal P-type layer structure, and an HCG structure is formed between the other end face of the P-type layer and the transparent conducting layer.

As a possible implementation manner, further, the P-type layer is a grating structure formed by patterning etching, and the high-contrast grating is used as a second mirror to provide optical confinement;

wherein the refractive index of the P type layer is larger than that of the transparent conductive layer.

As a preferred implementation choice, preferably, the cross section of the grating structure formed by the P-type layer through the patterned etching is a strip, a net or a column.

As a possible embodiment, further, the contact between the transparent conductive layer and the P-type layer is an ohmic contact.

As a possible embodiment, further, the support substrate is formed of a hard material.

As a preferred implementation choice, preferably, the first mirror is a dielectric DBR or metal mirror or HCG structure, and the reflectivity of the first mirror is smaller than that of the high-contrast grating.

As a preferred implementation option, it is preferable that the supporting substrate is formed of a metal or ceramic material, and the N electrode is formed of Cr, Au, Ni, Au, Ti, or Au material.

Based on the above structural scheme, the invention also provides a preparation method of the gallium nitride-based resonant cavity light-emitting diode, which comprises the following steps:

s1, growing a semiconductor epitaxial layer of a pin structure on the original substrate;

s2, etching p-GaN on the outer surface of the semiconductor epitaxial layer to form an HCG structure, and preparing a blank A;

s3, depositing a transparent conducting layer on the upper surface of the blank A to obtain a blank B;

s4, preparing a support substrate on the upper surface of the blank B to obtain a blank C;

s5, inverting the blank C, and then removing the original substrate to expose the end face of the semiconductor epitaxial layer far away from the support substrate;

s6, preparing an N electrode on the end face of the semiconductor epitaxial layer far away from the supporting substrate;

and S7, preparing a first reflector on the end face of the semiconductor epitaxial layer far away from the supporting substrate, and finishing the manufacture of the device.

As a preferred implementation option, step S1 is to grow a semiconductor epitaxial layer with a pin structure by using MOCVD or MBE;

the semiconductor epitaxial layer comprises an N-type layer, an active region and a P-type layer which are sequentially stacked on an original substrate;

the supporting substrate is formed by metal or ceramic materials and is prepared by electroplating, deposition or metal bonding.

Based on the above structural scheme, the invention further provides a vertical cavity surface emitting laser, which comprises the gallium nitride-based resonant cavity light emitting diode.

By adopting the technical scheme, compared with the prior art, the invention has the beneficial effects that: this scheme directly uses partial P type layer and transparent conducting layer as high contrast grating structure in order to replace traditional bottom reflector structure, has removed step and structure that other dielectric films need additionally grow as low refracting index medium and high refracting index medium of HCG among the traditional scheme from, and simultaneously, this scheme has realized having reduced device series resistance, reduces absorption loss's effect, has still improved the output light quality simultaneously.

In addition, the scheme adopts the form that a high-contrast grating structure is formed by a part of P-type layers and a transparent conducting layer and is used as a bottom reflector, compared with the traditional reflector scheme, the scheme adopts the HCG structure which has higher reflectivity than a metal mirror and has more excellent thermal performance than a DBR reflector. The use of HCG as the bottom mirror not only maintains its advantages of low loss, high reflectivity, polarization control, and strong phase matching and focusing capabilities, but also simplifies the structure and process. Furthermore, the HCG structure is also suitable for the vertical cavity surface emitting laser, and the characteristic of the HCG structure is favorable for further reducing the lasing threshold of the device.

In addition, the scheme realizes the polarization control of the resonant cavity light-emitting device by introducing a high-contrast grating structure; moreover, the method can realize the preparation of the high-efficiency gallium nitride-based resonant cavity light-emitting diode, has simple structure preparation process, is compatible with all preparation processes of standard semiconductor preparation processes, meets the requirement of large-scale photoelectric integration, and has wide application prospect.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic structural diagram of a gallium nitride-based resonant cavity light emitting diode according to an embodiment of the present invention;

FIG. 2 is one of schematic top views of a high contrast grating of the present invention used as a second mirror;

FIG. 3 is a second schematic diagram of a top view of the high contrast grating of the present invention used as a second mirror;

FIG. 4 is a third schematic diagram of a top view of the high contrast grating of the present invention used as a second mirror;

FIG. 5 is a flow chart of a method of making an embodiment of the present invention;

FIG. 6 is a schematic diagram of a sample structure after epitaxial growth;

FIG. 7 is a schematic structural diagram of a HCG structure formed by patterning and etching a P-type layer on the outer surface of a semiconductor epitaxial layer;

FIG. 8 is a schematic structural diagram of a transparent conductive layer deposited on a sample surface;

FIG. 9 is a schematic view of a sample structure after preparation of a metal support substrate;

FIG. 10 is a schematic view of the sample structure after inverting the sample and removing the original substrate;

FIG. 11 is a schematic diagram of the structure of a sample after preparation of an N-type electrode;

fig. 12 is a schematic view of a sample structure after preparation of the first mirror.

Detailed Description

The present invention will be described in further detail with reference to the accompanying drawings and examples. It is to be noted that the following examples are only illustrative of the present invention, and do not limit the scope of the present invention. Similarly, the following examples are only some but not all examples of the present invention, and all other examples obtained by those skilled in the art without any inventive work are within the scope of the present invention.

As shown in fig. 1, the gallium nitride-based resonant cavity light emitting diode of the present embodiment includes a supporting substrate 6, a high contrast grating 45, an active region 3, and an N-type layer 2, which are sequentially stacked, wherein a first reflector 8 and an N electrode 7 are further disposed on an end surface of the N-type layer 2 away from the active region;

the high-contrast grating 45 is composed of a P-type layer 4 and a transparent conducting layer 5, one end face of the P-type layer 4 is attached to the active region 3, an uneven grating structure is formed on the other end face of the P-type layer 4 through etching, the transparent conducting layer 5 is arranged in a gap and a surface of the grating structure of the P-type layer 4, namely, the portion, attached to the active region 3, of the P-type layer 4 serves as a normal P-type layer structure, an HCG structure (namely, a high-contrast grating structure) is formed between the other end face of the P-type layer 4 and the transparent conducting layer 5, and the transparent conducting layer 5 is in ohmic contact with the P-type layer 4.

In this embodiment, the P-type layer 4 is a grating structure formed by patterned etching, and the high-contrast grating 45 serves as a second mirror to provide optical confinement;

in this embodiment, the other end surface of the P-type layer 4 is patterned and etched to form a grating structure, and the specific grating structure may be a stripe (as shown in fig. 2), a mesh (as shown in fig. 3), a column (as shown in fig. 4), or the like, and the grating may be periodic or aperiodic, the etching pattern width of the grating is between 100 and 500nm, the period of the grating is between 200 and 1000nm, and the etching depth is between 1 and 200nm, and in this scheme, the grating may be but not limited to a sub-wavelength grating.

In the present embodiment, the shape of the patterned etching on the other end face of the P-type layer 4 is preferably a strip (as shown in fig. 2), a net (as shown in fig. 3), or a column (as shown in fig. 4). But is not limited thereto and in some embodiments the P-type layer 4 may be etched into other geometries as well.

As an alternative, in this embodiment, the transparent conductive layer 5 may be one of transparent conductive materials such as Indium Tin Oxide (ITO) and zinc oxide, but its refractive index is smaller than that of the P-type layer 4, and the larger the difference is, the better.

In this embodiment, the material of the N electrode 7 may be Cr, Au, Ni, Au, Ti, Au, or other metal electrode material with good conductivity or a stacked structure of different metal materials.

In this embodiment, the first reflector 8 is a dielectric DBR, and the reflectivity of the first reflector 8 is smaller than that of the high-contrast grating 45(HCG) to improve the light output power.

In other embodiments, the first reflector 8 may also adopt an HCG structure, and the high refractive index material may be TiO₂、Ti₃O₅、Ta₂O₅、ZrO₂、HfO₂One of the materials, the low refractive index material can be SiO₂、Al₂O₃MgO or air.

As a possible embodiment, further, the supporting substrate 6 is formed of a hard material, in particular, the supporting substrate 6 is formed of a metal or ceramic material or other kind of hard material, which is prepared by electroplating, deposition or metal bonding.

In other embodiments, the first mirror 8 may also be a metal mirror.

Since the P-type layer 4, the active region 3, and the N-type layer 2 in this embodiment may all adopt the existing P-type layer, active region, and N-type layer structures, which are already well-established in the prior art, further description is omitted.

Based on the above structural scheme, referring to and shown in fig. 5, this embodiment further provides a method for manufacturing a gallium nitride-based resonant cavity light emitting diode, which includes the following steps:

s1, growing a semiconductor epitaxial layer with a pin structure on the original substrate 1, specifically, as shown in fig. 6, growing a semiconductor epitaxial layer with a pin structure on the original substrate 1 by using MOCVD or MBE, wherein an N-type layer 2, an active region 3, and a P-type layer 4 are sequentially grown on the original substrate 1 to form a semiconductor epitaxial wafer, and the original substrate 1 is generally made of GaN, sapphire, Si, SiC, or other substrates;

s2, etching P-GaN on the outer surface of the semiconductor epitaxial layer to form an HCG structure, and preparing a blank A, specifically, as shown in FIG. 7, preparing a grating structure on the upper surface of the P-type layer by using processes such as nanoimprint, dry etching and the like;

s3, depositing a transparent conductive layer 5 on the upper surface of the blank a to obtain a blank B, specifically, as shown in fig. 8, depositing Indium Tin Oxide (ITO) on the gap and surface of the P-type layer grating by magnetron sputtering to form the transparent conductive layer 5, or depositing other transparent conductive materials such as zinc oxide;

s4, preparing a supporting substrate 6 on the upper surface of the blank B to obtain a blank C, specifically, as shown in fig. 9, preparing a metal supporting substrate 6 on the upper surface of the transparent conductive layer 5 by using an electroplating or metal bonding method, where the thickness of the metal supporting substrate 6 may be tens to hundreds of micrometers, and the metal supporting substrate 6 may be copper, aluminum or other metal materials with good thermal and electrical conductivity;

s5, inverting the blank C, and then removing the original substrate 1 to expose the end surface of the semiconductor epitaxial layer away from the support substrate, specifically, as shown in fig. 10, inverting the blank C formed in step S4 and removing the original substrate 1 during epitaxial growth by using a laser lift-off, polishing or etching method, where after removing the original substrate 1, the metal support substrate 6 plays a role in supporting the semiconductor epitaxial layer;

s6, preparing an N electrode on the end surface of the semiconductor epitaxial layer far from the supporting substrate 6, specifically, as shown in fig. 11, preparing an N electrode 7 on the upper surface of the N-type layer 2 by sputtering or evaporation, and the material thereof may be Cr, Ni, Pt, Ti, Au, or other metal electrode materials with good conductivity or a stack of different metal materials;

s7, preparing the first mirror 8 on the end surface of the semiconductor epitaxial layer far from the supporting substrate 6, and completing the device fabrication, specifically, as shown in fig. 12, the first mirror 8 may be prepared by deposition, evaporation, or the like, and may adopt a metal mirror, a dielectric film DBR, or an HCG structure. In this embodiment, a dielectric film DBR is used, and the reflectivity is smaller than that of the bottom mirror.

According to the scheme, part of the P-type layer and the transparent conducting layer are directly adopted as the high-contrast grating structure to replace a traditional bottom reflector, so that the additional growth of other dielectric films as a low-refractive-index medium and a high-refractive-index medium of HCG is avoided, the process difficulty of the device is effectively reduced, and the process flow is simplified. Meanwhile, compared with other reflectors, the HCG structure has higher reflectivity than a metal reflector and has more excellent thermal performance than a DBR reflector, the series resistance and the self-generated heat of the device are effectively reduced, and the thermal stability of the device is improved. In addition, the high contrast grating junction has a high reflectivity for light with a polarization direction perpendicular to the grating and a low reflectivity for light with a polarization direction parallel to the grating, so that a sufficiently high gain can be obtained in the device only for light with a polarization direction perpendicular to the grating. This polarization control method is currently the most effective polarization control method. The use of HCG as the bottom mirror not only maintains its advantages of low loss, high reflectivity, polarization control, and strong phase matching and focusing capabilities, but also simplifies the structure and process. Furthermore, the HCG structure is also suitable for the vertical cavity surface emitting laser, and the characteristic of the HCG structure is favorable for further reducing the lasing threshold of the device.

The invention is prepared by processes of nano-imprinting, etching, electroplating, deposition and the like, can realize the preparation of the gallium nitride-based high-efficiency resonant cavity light-emitting diode, is compatible with all preparation processes of standard semiconductor preparation processes, meets the requirements of large-scale photoelectric device preparation and integration, and has wide application prospect.

The above description is only a preferred embodiment of the application and is illustrative of the principles of the technology employed. It will be appreciated by those skilled in the art that the scope of the invention herein disclosed is not limited to the particular combination of features described above, but also encompasses other arrangements formed by any combination of the above features or their equivalents without departing from the inventive concept. For example, the above features may be replaced with (but not limited to) features having similar functions disclosed in the present application.