Nitride-based semiconductor laser device and method for the production thereof

A method for the production of a nitride-based semiconductor laser device having:

• (A) a first contacting layer formed on a substrate,
• (B) a first electrode formed on the first contacting layer,
• (C) a first cladding layer formed on the first contacting layer,
• (D) an active layer formed on the first cladding layer,
• (E) a second cladding layer formed on the active layer,
• (F) a second contacting layer formed on the second cladding layer, and
• (G) a second electrode formed on the second contacting layer,
• the second cladding layer comprising a lower layer and an upper layer,
• the first contacting layer, the first cladding layer, the active layer, the second cladding layer and the second contacting layer each being composed of a nitride-based compound semiconductor layer,
• the first cladding layer, the active layer and the lower layer of the second cladding layer forming a mesa structure,
• the upper layer of the second cladding layer and the second contacting layer having a ridge structure having a width smaller than a width of the mesa structure,
• the second electrode having a width substantially the same as a width of the second contacting layer at an interface of the second contacting layer and the second electrode,
• an insulating layer formed on the portions of the lower layer of the second cladding layer which portions correspond to a top surface of the mesa structure, said insulating layer covering at least part of each of both side surfaces of the upper layer of the second cladding layer, and
• a metal layer being formed on a top surface of the insulating layer and a top surface of the second electrode such that the metal layer continues from the top surface of the insulating layer to the top surface of the second electrode, said metal layer having a width substantially the same as the width of the mesa structure,
• said method comprising the steps of:
• (a) consecutively depositing the first contacting layer, the first cladding layer, the active layer, the second cladding layer and the second contacting layer on the substrate, and then forming the second electrode having substantially the same width as the second contacting layer on the second contacting layer;
• (b) while using the second electrode as an etching mask, etching the second contacting layer and further partly etching the second cladding layer in the second cladding layer thickness direction, to form the second contacting layer and the upper layer of the second cladding layer having the ridge structure and to form the lower layer of the second cladding layer having top surfaces of which are exposed on both sides of the upper layer of the second cladding layer;
• (c) forming the insulating layer on the portions of the lower layer of the second cladding layer on which portions no upper layer of the second cladding layer is formed, so as to cover at least part of each of both side surfaces of the upper layer of the second cladding layer and to expose the top surface of the second electrode;
• (d) forming the metal layer having substantially the same width as the width of the mesa structure to be formed, on the insulating layer and the top surface of the second electrode such that the metal layer continues from the surface of the insulating layer to the top surface of the second electrode;
• and
• (e) while using the metal layer as an etching mask, etching at least the insulating layer, the lower layer of the second cladding layer, the active layer and the first cladding layer, to form the mesa structure.