Methods for making light emitting diodes and optical elements

A method for making a light emitting diode, comprising steps of:

• providing a substrate having a first surface;
• forming a first semiconductor layer, an active layer, and a second semiconductor pre-layer on the first surface;
• electrically connecting a first electrode with the first semiconductor layer and a second electrode with the second semiconductor pre-layer;
• and
• applying a patterned mask layer on a second semiconductor pre-layer surface away from the active layer, wherein the patterned mask layer comprises a plurality of linear walls aligned side by side, and a groove is defined between each adjacent linear walls to form an exposed portion of the second semiconductor pre-layer;
• and
• etching the exposed portion of the second semiconductor pre-layer surface and removing the patterned mask layer to form a plurality of three-dimensional structures, wherein during the step of etching the exposed portion of the second semiconductor pre-layer surface, the patterned mask layer remains;
• the plurality of three-dimensional structures are linear protruding structures, and a cross-section of each linear protruding structure is an arc, the step of etching the exposed portion of the second semiconductor pre-layer surface is carried out in a microwave plasma system capable of producing a reactive atmosphere, the reactive atmosphere comprises chlorine gas and argon gas, a chlorine input flow rate is lower than an argon input flow rate, and the chlorine input flow rate is in a range from about 4 standard-state cubic centimeters per minute to about 20 standard-state cubic centimeters per minute, and the argon input flow rate is in a range from about 10 standard-state cubic centimeters per minute to about 60 standard-state cubic centimeters per minute.