Patent Application
20220059989
The disclosure relates to a semiconductor light-emitting diode, and more particularly to a laser diode and a method for making the same.
GaN-based light-emitting diodes (LEDs) and laser diodes are extensively researched and profusely applied in the market, especially in the fields of laser display and laser projection, such as GaN-based blue or green-colored laser diodes, which mainly has an edge-emitting ridge-waveguide structure. For a laser diode to adopt the edge-emitting ridge-waveguide structure, distributed Bragg reflection (DBR) mirrors are plated on both ends of a laser bar in order to form a Fabry-Pérot cavity that is used for resonance. Conventional Fabry-Pérot cavity surfaces are all right-angled, which results in poor coverage of the DBR mirrors on the edges of the cavity and easy breakage when under high stress. Moreover, side-plated DBR cover layers may adversely affect the eutectic structure of the laser diode, thereby affecting electrical properties of the laser diode.
Therefore, an object of the disclosure is to provide a laser diode that can alleviate at least one of the drawbacks of the prior art.
According to a first aspect of the present disclosure, there is provided a laser diode that includes:
According to a second aspect of the present disclosure, there is provided a method for making a laser diode. The method includes the steps of:
forming a light-emitting stack, the light-emitting stack having an N-type layer, an active layer and a P-type layer, the P-type layer being formed with a ridged member;
cleaving the ridged member in a direction perpendicular to a lengthwise direction of the ridged member to obtain a first inclined surface at an end face where the ridged member is cleaved; and
growing a DBR cover layer that covers the light-emitting stack, a contact interface between the DBR cover layer and the ridged member including the first inclined surface.
Other features and advantages of the disclosure will become apparent in the following detailed description of the embodiment(s) with reference to the accompanying drawings, of which:
Before the disclosure is described in greater detail, it should be noted that where considered appropriate, reference numerals or terminal portions of reference numerals have been repeated among the figures to indicate corresponding or analogous elements, which may optionally have similar characteristics.
In addition, in the description of the present disclosure, the terms “outward”, “inward”, “upward”, “downward”, “top”, “bottom”, “front” are meant to indicate relative position between the elements of the disclosure, and are not meant to indicate the actual position of each of the elements in actual implementations.
Referring to
Referring to
In some embodiments, an angle between the first inclined surface 7 and a normal to a bottom surface of the ridged member 2 ranges between 0° and 60°, which ensures that the DBR cover layer 8 properly covers the ridged member 2 and does not peel off easily.
Referring to
In some embodiments, the second inclined surface 9 has an angle with a normal to a top surface of the substrate 3 that ranges between 0° and 60°, which ensures that the DBR cover layer 8 properly covers the substrate 3 and does not peel off easily.
In some embodiments, the first inclined surfaces 7 are disposed on the P-type layer 6. In the process of forming the first inclined surfaces 7, the first inclined surfaces 7 do not extend into the active layer 5.
In some embodiments, the N-type layer 4 includes an N-type metal layer 41. The N-type metal layer 41 is used for connecting the N-type layer 4 and conducting electricity.
In some embodiments, the P-type layer 6 includes a P-type metal layer 62. The P-type metal layer 62 is used for connecting the P-type layer 6 and conducting electricity.
In some embodiments, the P-type layer 6 further includes an upper waveguide layer 61. The upper waveguide layer 61 may be, but not limited to, a P-InGaN layer. The first inclined layers 7 are made by forming grooves 1 (see
Referring to
In step S1, a light-emitting stack is formed on the substrate 3. The light-emitting stack has the N-type layer 4, the active layer 5, and the P-type layer 4. The P-type layer 6 is formed with the ridged members 2.
In step S2, the ridged members 2 are cleaved (see
In step 3, a DBR cover layer 8 that covers and contacts the substrate 3 and the light-emitting stack is grown by using vacuum coating, which may include magnetron sputtering, electron cyclotron resonance (ECR) deposition or chemical vapor deposition. A contact interface between the DBR cover layer 8 and each ridged member 2 includes the first inclined surfaces 7. In this embodiment, the active layer 5 is a multi-quantum well (MQW) active layer. An angle between the first inclined surface 7 and a normal to a bottom surface of the ridged member 2 ranges between 0° and 60°, which ensures that the DBR cover layer 8 properly covers the ridged member 2 and does not peel off easily.
Since the contact interface layer includes the first inclined surface 7, problems such as poor coverage of the DBR and easy breakage when under high stress caused by a right-angled cavity surface and adverse effects on the eutectic structure of the laser diode that affects the electrical properties of the laser diode caused by side-plated DBR are solved.
Another embodiment of the method for making the laser diode further includes step S4 in addition to steps S1, S2, S3. In step S4, the substrate 3 is cleaved after the ridged members 2 are cleaved to obtain the first inclined surfaces 7. In particular, the substrate 3 is cleaved in a direction perpendicular to the lengthwise direction of the ridged member 2 to obtain second inclined surfaces 9 at end faces where the substrate 3 is cleaved. A contact interface between the substrate 3 and the DBR cover layer 8 includes the second inclined surfaces 9. A two-sided wedge-shaped laser diode is thus obtained. In some embodiments, the second inclined surface 9 forms an angle with a normal to a top surface of the substrate 3 that ranges between 0° and 60°, which ensures that the DBR cover layer 8 properly covers the substrate 3 and does not peel off easily.
The two-sided wedge-shaped laser diode obtained from the aforementioned steps has a double inclined surface structure formed cooperatively by the first inclined surfaces 7 and the second inclined surfaces 9 so that the DBR cover layer 8 has a better coverage of the substrate 3 and does not peel off easily, which ensures good electrical conductivity of the laser diode.
Referring to
In some embodiments, cleaving the substrate 3 includes the steps of forming a second groove 1′ (see
The first and second grooves 1, 1′ extend in a direction perpendicular to the lengthwise direction L1 of the ridged member 2, i.e. L2 is perpendicular to L1. The first and second grooves 1, 1′ may be made by, but not limited to, using a yellow light process and an inductive coupled plasma (ICP) etching process.
Referring back to
In view of the aforementioned, the method for making the laser diode of the present disclosure not only can ease fabrication of DBR cover layers for laser diodes, but can solve the drawbacks of right-angled cavity surfaces such as poor DBR coverage and easy breakage under high stress, which cause the side-plated DBR to adversely affect the eutectic structure of the laser diode and hence leads to poor electrical properties of the laser diode. In addition, since a portion of the contact interface at the end face is etched to improve the coverage of the DBR, the current density near the contact interface is reduced, and the laser diode is capable of resisting catastrophic optical damage (COD).
In the description above, for the purposes of explanation, numerous specific details have been set forth in order to provide a thorough understanding of the embodiments. It will be apparent, however, to one skilled in the art, that one or more other embodiments may be practiced without some of these specific details. It should also be appreciated that reference throughout this specification to “one embodiment,” “an embodiment,” an embodiment with an indication of an ordinal number and so forth means that a particular feature, structure, or characteristic may be included in the practice of the disclosure. It should be further appreciated that in the description, various features are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of various inventive aspects, and that one or more features or specific details from one embodiment may be practiced together with one or more features or specific details from another embodiment, where appropriate, in the practice of the disclosure.
While the disclosure has been described in connection with what are considered the exemplary embodiments, it is understood that this disclosure is not limited to the disclosed embodiments but is intended to cover various arrangements included within the spirit and scope of the broadest interpretation so as to encompass all such modifications and equivalent arrangements.
This application is a bypass continuation-in-part (CIP) application of PCT International Application No. PCT/CN2019/088883, filed on May 28, 2019. The entire content of the international patent application is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2019/088883 | May 2019 | US |
| Child | 17493602 | US |
