A method for fabricating a group-III nitride semiconductor laser device, comprising the steps of:
- preparing a substrate product having a substrate and a semiconductor region, the substrate comprising a hexagonal group-III nitride semiconductor and including a semi-polar principal surface, the semiconductor region provided on the semi-polar principal surface and including an active layer;
- scribing a first surface of the substrate product to form a plurality of scribe marks extending along an a-axis of the hexagonal group-III nitride semiconductor;
- and
- forming a laser bar and a substrate product residue from the substrate product with a cleaving system,
- wherein, the cleaving system includes a support member supporting the substrate product, a stretchable protective sheet protecting the first surface of the substrate product facing the support member when the substrate product is supported by the support member, a blade forced down through the substrate product toward the support member from a second surface of the substrate product opposite to the first surface when the substrate product is supported by the support member, and a movable member movable relative to the support member and adjusting the tension of the protective sheet,
- the protective sheet extends in the direction of a reference axis and is disposed between the substrate product and the support member while both edges of the protective sheet intersecting the reference axis are fixed to the support member,
- the substrate product is disposed over the protective sheet and the support member such that the a-axis intersects the reference axis, the substrate product comprising a first region and a second region,
- the first region and the second region are disposed in sequence in a direction intersecting the a-axis,
- the interface of the first region and the second region extends along the a-axis,
- the first region includes a scribe mark at the furthest end among the scribe marks,
- the step of forming the laser bar and the substrate product residue includes the steps of:
- holding the substrate product with the support member such that the first region protrudes from an edge of the support member and the second region is disposed over the support member;
- putting the blade into contact with an area included in the first region of the second surface in a direction along a normal vector extending along a normal axis of the semi-polar principal surface of the substrate;
- and
- forcing the blade down through the first region such that the first region is squeezed between the support member and the movable member together with a part of the protective sheet in contact with the first region while increasing the tension generated in the area of the protective sheet using the movable member to generate a force in the first region in a direction opposite to the direction of travel of the blade toward the first region, until the semi-polar principal surface at an end face of the first region tilts by a deflection angle THETA from the semi-polar principal surface of the second region,
- the laser bar extends from the first surface to the second surface and has a first end surface and a second end surface formed by separation,
- the first end surface and the second end surface constitute a laser cavity of the group-III nitride semiconductor laser device,
- a c-axis vector representing the direction of a c-axis of the hexagonal group-III nitride semiconductor tilts by an angle ALPHA from a normal vector of the semi-polar principal surface of the substrate,
- an area in the first region in contact with the blade extends along the a-axis,
- the deflection angle THETA is defined in the c-m plane, the c-m plane being defined by the c-axis and an m-axis of the hexagonal group-III nitride semiconductor, the deflection angle THETA having a positive value when the substrate product bends in the direction from the m-axis to the c-axis, having a negative value when the substrate product bends in the direction from the c-axis to the m-axis, being within a range of 11 degrees to 19 degrees if the angle ALPHA is within a range of 71 degrees to 79 degrees, and being within a range of −19 degrees to −11 degrees if the angle ALPHA is within a range of 101 degrees to 109 degrees, and
- the first end surface and the second end surface intersect the c-m plane.