Quantum well structure, chip processing method, chip, and laser

A method for processing a chip, comprising:

• processing a chip-layer group on a substrate;
• removing part of the chip-layer group to form a waveguide region;
• processing a capping layer by growth;
• processing the capping layer at the waveguide region into a waveguide strip with an end surface facing the chip-layer group, and removing part of the waveguide strip attached to the chip-layer group to define a gap between the waveguide strip and the chip-layer group;
• and
• processing a waveguide cladding, and removing the waveguide cladding corresponding to the chip-layer group and the waveguide cladding corresponding to the gap.

A chip, comprising:

• a substrate having a chip region and a waveguide region;
• a chip-layer group disposed at the chip region of the substrate, wherein the chip-layer group comprises:
• a buffer layer with a thickness of 1 μm-1.5 μm on the substrate;
• a lower graded-buffer-layer with a thickness of 10 nm-100 nm;
• a quantum well structure with a thickness of 10 nm-30 nm, wherein the quantum well structure for a distributed feedback (DFB) laser chip comprises:
• a plurality of indium aluminum arsenide (InAlAs) quantum well layers;
• and
• a plurality of indium aluminum gallium arsenide (InAlGaAs) quantum well layers, wherein a thickness of each of the plurality of InAlGaAs quantum well layers is the same as a thickness of each of the plurality of InAlAs quantum well layers, and one InAlGaAs quantum well layer is disposed between two adjacent InAlAs quantum well layers, wherein
• the thickness of each of the plurality of InAlAs quantum well layers ranges from 0.4 nm to 0.6 nm, and the number of the plurality of InAlAs quantum well layers ranges from 3 to 17;
• an upper graded-buffer-layer with a thickness of 10 nm-100 nm;
• a grating layer;
• and
• a corrosion stop layer with a thickness of 10 nm-50 nm;
• a waveguide strip spaced apart from the chip-layer group and integrated at the waveguide region of the substrate, and configured to guide a light spot of laser light emitted to be substantially circular;
• and
• a waveguide cladding deposited on the waveguide strip.