Patent ID: 7605527

Claim:
A discharge lamp comprising: a sealed-off tube filled with a discharge gas; and a discharge electrode provided in the sealed-off tube comprising: a supporting base having a flat top surface, formed of a wide bandgap semiconductor, wherein an electron-emitting layer is provided at an upper portion of the supporting base, implemented by a plurality of protrusions separated by a plurality of grooves cut from the top surface toward a bottom surface of the supporting base, wherein the depth of the grooves are smaller than a thickness of the supporting base, the top end surfaces of the protrusions are parallel to the top surface of the supporting base, for each protrusion viewed from above a perpendicular center line from the plane of the top end surface of the protrusion, at least a part of sidewalls of the protrusion are unseen, and dangling bonds of the wide bandgap semiconductor at the unseen sidewalls are terminated with hydrogen atoms.