A PIN diode comprising an N-type substrate comprising a cathode of the PIN diode and having an intrinsic layer disposed upon the N-type substrate and having a top surface a P-type material disposed upon the top surface of the intrinsic layer comprising an anode of the PIN diode and a N-type material disposed over the sidewall of the cathode and over the sidewall and a portion of the top surface of the intrinsic material that is not occupied by the anode, wherein a horizontal gap is defined between the anode and the cathode through the intrinsic material, the gap being variable in width and/or the horizontal gap is less than the thickness of the intrinsic layer.