NOVELTY - The optical device comprises: a gallium- and nitrogen-containing substrate having an off-axis non-polar oriented crystalline surface plane; a gallium- and nitrogen-containing epitaxial layer overlying the off-axis non-polar oriented crystalline surface plane; and a surface region overlying the gallium- and nitrogen-containing epitaxial layer, where 90% of the surface region is free from hillocks with lengths of 100-200 mu m, with a pyramidal-like shape and with a rectangular footprint that is elongated in an a-plane direction.    USE - The optical device is useful as a laser diode (claimed), LED, solar cells, a photoelectrochemical water splitting and hydrogen generation device, photodetectors, integrated circuits, and transistors.    ADVANTAGE - The optical device has simple structure, reduced cost, and the surface region free from hillocks or other surface imperfections so that performance, reliability, intensity and efficiency can be effectively enhanced.    DETAILED DESCRIPTION - The optical device comprises: a gallium- and nitrogen-containing substrate having an off-axis non-polar oriented crystalline surface plane; a gallium- and nitrogen-containing epitaxial layer overlying the off-axis non-polar oriented crystalline surface plane; and a surface region overlying the gallium- and nitrogen-containing epitaxial layer, where 90% of the surface region is free from hillocks with lengths of 100-200 mu m, with a pyramidal-like shape and with a rectangular footprint that is elongated in an a-plane direction. The off-axis non-polar oriented crystalline surface plane is defined from the non-polar (10-10) plane with a negative angle or an angle of 0 degrees to a predetermined angle toward either or both the c-plane (0001) and the a-plane. A magnitude of the negative angle is greater than 1.2 degrees . The optical device is set for overlying the gallium nitride containing epitaxial layer. The gallium- and nitrogen-containing epitaxial layer comprises the surface region. The gallium- and nitrogen-containing epitaxial layer comprises multiple quantum wells or multiple layers, where n-type and p-type regions of the multiple quantum wells or multiple layers are formed by an atmospheric pressure epitaxial formation process. The quantum well has thickness of 3.5 nm. The atmospheric pressure is 700-800 Torr. The off-axis non-polar oriented crystalline surface plane has an on-axis orientation.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of various miscuts/offcuts in planes.