A photovoltaic device and method include a substrate coupled to an emitter side structure on a first side of the substrate and a back side structure on a side opposite the first side of the substrate. The emitter side structure or the back side structure include layers alternating between wide band gap layers and narrow band gap layers to provide a multilayer contact with an effectively increased band offset with the substrate and/or an effectively higher doping level over a single material contact. An emitter contact is coupled to the emitter side structure on a light collecting end portion of the device. A back contact is coupled to the back side structure opposite the light collecting end portion.

A photovoltaic device includes a digital alloy buffer layer including a plurality of alternating layers of semiconductor material. An absorption layer epitaxially is grown on the digital alloy buffer layer, an intrinsic layer is formed on the absorption layer and a doped layer is formed on the intrinsic layer. A conductive contact is formed on the doped layer.

The present disclosure provides a photo sensing device and a method for forming a photo sensing device. The photo sensing device includes a substrate, a photosensitive member, a superlattice layer and a diffusion barrier structure. The substrate includes a silicon layer at a front surface. The photosensitive member extends into and at least partially surrounded by the silicon layer, wherein an upper portion of the photosensitive member protruding from the silicon layer has a top surface and a facet tapering toward the top surface. The superlattice layer is disposed between the photosensitive member and the silicon layer. The diffusion barrier structure is disposed at a first side of the photosensitive member and a bottom of the diffusion barrier structure is at a level below a top surface of the silicon layer, wherein at least a portion of the diffusion barrier structure is laterally surrounded by the silicon layer.

A semiconductor-graphene heterojunction quad-detector pairs a semiconductor material with curved graphene strips in a quad-cell design. Graphene has been shown to have exceptional electrical properties that enhance the operation of semiconductor photodetectors. These properties address limitations of current semiconductor quad-cell devices by drastically increasing their sensitivity. According to an aspect of the present disclosure, a position detector includes a substrate having windows formed therein. Four graphene pads each having a plurality of curved strips are formed on the substrate. Each of the plurality of curved strips have a first end connected to a grounded conductor pad and a second end connected to one of four signal conductor pads.

An avalanche photodiode includes a silicon layer on a substrate; a germanium layer on the silicon layer; and a plurality of contacts including a cathode, an anode, and at least two separate gain tuning contacts configured to adjust an electric field to tune multiplication of carriers. The at least two separate gain tuning contacts are configured to control the electric field in the germanium layer and silicon layer. The at least two separate gain tuning contacts are configured to tailor the electric field such that the multiplication of carriers is greater in the silicon layer than the germanium layer. This added gain tuning control can be used to tailor the electric field profile such that multiplication happens mostly in silicon to achieve lower excess noise and little to no bandwidth variation.