Abstract: A visible-light light emitting diode having a center wavelength of 400 to 560 nm formed on a patterned sapphire substrate and with a four-layer quantum well as an active layer. The patterned sapphire substrate can include a plurality of recesses having openings and a plurality of convex portions on one surface thereof, the recesses being integrally formed between the neighboring convex portions or a plurality of convex portions on one surface thereof, a recess being defined between two of the neighboring convex portions and wherein the convex portions on the surface are made of dielectric material. A lens layer is disposed on an upper P-type doped region.

Abstract: A homojunction type high-speed photodiode has an active area of greater than at least 50 microns (?m) or preferably greater than 60 microns (?m) in diameter, which has an p-i-n junction epitaxial layer formed on a semiconductor substrate and includes a first ohmic contact layer, an absorption layer, a collector layer and a second ohmic contact layer. No more absorbance occurs in the collector layer of InGaAs, by means of completely absorbing the photon energy in advance by the absorption layer in which the absorption layer has powerful optical absorption constant. Not only can the prior art problems be solved, such as surface absorbance, but also improved electron transport can be achieved by using InGaAs as the constructing material, compared to other materials. The resistance capacitance (RC) for the entire structure can be significantly reduced, and the limitations to the bandwidth resulted from the carrier transport time can be improved.