Method of manufacturing substrate for forming device, and method of manufacturing nitride-based semiconductor laser diode

1. A method of manufacturing a substrate for forming a device, the method comprising:

preparing a GaN substrate of which an a-plane or an m-plane is selected as a main plane;

masking the entirety of a surface of the main plane of the GaN substrate; and

applying etching liquid to the entirety of the surface of the masked GaN substrate, wherein the entirety of the main plane of the GaN substrate is unexposed to the etching liquid, thereby forming a crystallographic surface on the a-plane or m-plane that is exposed to the etching liquid and whichever is not the selected main plane.

2. The method according to claim 1 , wherein KOH is used as the etching liquid.

3. A method of manufacturing a semiconductor laser diode, the method comprising:

preparing a GaN substrate of which an a-plane or m-plane is selected as a main plane;

masking the entirety of a surface of the main plane of the GaN substrate;

applying etching liquid to the entirety of the surface of the masked GaN substrate, wherein the entirety of the main plane of the GaN substrate is unexposed to the etching liquid, thereby forming a crystallographic surface of the a-plane or m-plane, whichever is not the selected main plane;

forming a GaN layer on the main plane of the GaN substrate;

forming a plurality of laser diode structures on the GaN layer;

etching the GaN substrate such that a cutting reference line is formed as a groove in the direction of the a-plane or m-plane, whichever is the selected main plane; and

cutting the GaN substrate along the cutting reference line so as to form a mirror surface of the semiconductor laser diode, the mirror surface coinciding with the cut surface of the a-plane or m-plane whichever is not the selected main plane.

4. The method according to claim 3 , wherein the preparing of the GaN substrate includes the steps of:

preparing an r-plane sapphire substrate; and

forming an a-plane or m-plane GaN layer on the r-plane sapphire substrate.

5. The method according to claim 3 , where the etching of the GaN substrate includes the steps of:

applying a mask onto the GaN substrate having laser diode structures formed thereon such that a region where the cutting reference line is to be formed is exposed.

6. The method according to claim 5 , wherein the etching of the GaN substrate is performed using KOH etching liquid.

7. The method according to claim 3 , wherein the cutting reference line is formed by etching only portion of the GaN substrate in the thickness direction of the GaN substrate.

8. The method according to claim 3 , wherein the cutting reference line is formed by etching the GaN substrate such that the sapphire substrate is exposed.