Patent attributes
The present invention provides a front-illuminated avalanche photodiode (APD) with improved intrinsic responsivity, as well as a method of fabricating such a front-illuminated APD. The front-illuminated APD comprises an APD body of semiconductor material, which includes a substrate and a layer stack disposed on a front surface of the substrate. The layer stack includes an absorption layer, a multiplication layer, and a field-control layer. Advantageously, a back surface of the APD body is mechanically and chemically polished, and a reflector having a reflectance of greater than 90% at the absorption wavelength band is disposed on the back surface of the APD body. Thus, incident light that is not absorbed in a first pass through the absorption layer is reflected by the reflector for a second pass through the absorption layer, increasing the intrinsic responsivity of the front-illuminated APD.
