Semipolar Nitride Laser Fractured Facets Low Threshold Current
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Solution Overview
Problem
Group-III nitride semiconductor laser devices with semipolar surfaces tilted relative to the c-axis face challenges in achieving low threshold current due to difficulties in forming high-quality, perpendicular, and flat laser cavity mirrors without ion damage using conventional dry etching methods.
Innovation Solution
A group-III nitride semiconductor laser device with a semipolar surface tilted towards the m-axis, featuring fractured facets that intersect with the m-n plane, allowing for a laser waveguide orientation that reduces threshold current, and a method of fabricating these devices using scribing and pressing techniques to form end faces without dry etching, ensuring flatness and perpendicularity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional dry etching methods are used to form laser cavity mirrors, then the mirrors can be formed on semipolar surfaces, but the facets suffer from ion damage, poor flatness, and lack of perpendicularity
Solution Approach 1:
The patent extracts the harmful ion bombardment step from the mirror formation process by replacing reactive ion etching with a mechanical fracturing method. The laser cavity mirrors are formed by cleaving the semiconductor crystal along natural fracture planes, completely eliminating ion damage while achieving atomically flat surfaces with excellent perpendicularity to the waveguide direction.
Solution Approach 2:
The patent replaces the chemical-mechanical dry etching system with a pure mechanical fracturing system. By applying controlled mechanical stress to the semiconductor crystal, natural cleavage planes form that are inherently flat and perpendicular, substituting the complex etching chemistry and ion bombardment with simple mechanical fracture mechanics.
2Use of energy by moving object
If the laser waveguide extends along the plane defined by the c-axis and m-axis to achieve low threshold current, then the transition energy is minimized, but conventional cleaved facets cannot be used for laser cavity mirrors
Solution Approach 1:
Instead of trying to adapt conventional cleaved facets (c-planes, a-planes, m-planes) to the new waveguide orientation, the patent inverts the approach by allowing the fracture faces to naturally form at the required orientation. The mechanical fracturing process automatically produces surfaces that are perpendicular to the waveguide extending along the c-axis and m-axis plane, eliminating the need to force conventional facet geometries.
3Reliability
If dry etching is used to form laser cavity mirrors, then mirrors can be created on semipolar surfaces, but the process conditions are difficult to optimize and require heavy burden of process development
Solution Approach 1:
The patent employs the self-service principle by utilizing the natural fracture properties of the semiconductor crystal itself to form the laser cavity mirrors. The crystal structure automatically provides the required flatness and perpendicularity through its inherent cleavage planes, eliminating the need for complex process optimization and heavy process development burden associated with dry etching parameter tuning.
Data Source
AI summary
Provided is a group-III nitride semiconductor laser device with a laser cavity allowing for a low threshold current, on a semipolar surface of a support base in which the c-axis of a hexagonal group-III nitride is tilted toward the m-axis. First and second fractured faces 27, 29 to form the laser cavity intersect with an m-n plane. The group-III nitride semiconductor laser device 11 has a laser waveguide extending in a direction of an intersecting line between the m-n plane and the semipolar surface 17a. For this reason, it is feasible to make use of emission by a band transition enabling the low threshold current. In a laser structure 13, a first surface 13a is opposite to a second surface 13b. The first and second fractured faces 27, 29 extend from an edge 13c of the first surface 13a to an edge 13d of the second surface 13b. The fractured faces are not formed by dry etching and are different from conventionally-employed cleaved facets such as c-planes, m-planes, or a-planes.