The channeling avalanche photodiode: A novel ultra-low-noise interdigitated p-n junction detector

A novel avalanche photodiode (APD) concept, the channeling APD, is proposed. Using a new interdigitated p-n junction structure, electrons and holes are spatially separated and impact ionize in layers of different band gap. Thus the effective ionization-rates ratio can be made extremely high (κ = α/β > 100), while maintaining a high gain, by a proper choice of the band gap difference. In the limit of large κ, this device mimics a channeltron photomultiplier. This structure can be fabricated using most III-V lattice matched heterojunctions, including long-wavelength materials for fiber-optical communications ( µm). The design of three channeling APD\´s using Al0.45Ga0.55As/ GaAs, InP/In0.53Ga0.47As, and AlAs0.08Sb0.92/GaSb heterojunctions is discussed in detail. Other important features of this structure are the unique capacitance-voltage characteristic, which may be important in varactor diode applications, and the interdigitized geometry which allows the depletion of large volumes of semiconductor materials doped to levels as high as 10¹⁷/cm³. This novel semiconductor device may find interesting applications also for FET\´s and integrated p-i-n-FET receivers and may be used for studies of high-field transport phenomena (e.g., drift velocities) over a wide range of electric fields.