InP-based optical receiver/2 × 2 crosspoint switch for high speed optical communications

A monolithically integrated circuit consisting of two InGaAs PINs, JFET preamplifiers, a 2 × 2 crosspoint switch, and output buffers was fabricated. It can convert two high-speed optical signals to electrical signals and subsequently amplify and route the signals to either of two output buffers. To minimize capacitance, the devices are fabricated in semi-insulating InP:Fe substrates using a horizontally-integrated planar technology. The InGaAs PIN photodetectors are grown by vapor phase epitaxy in recessed wells and are subsequently planarized so that they are level with the top of the InP:Fe substrate using reactive ion etching. Both n and p contacts are made from the top of the wafer. The JFETs and load resistors are fully ion-implanted using Si for n-type implants and a coimplant of Be and As to achieve a stable p-type implant. The electrical signals are amplified by inverting amplifiers which are connected to the inputs of the 2 × 2 crosspoint switch. Each switch cell consists of two series FETs with an intermediate shunt FET which can provide a low resistance path to a bias voltage when turned on. Optical signals of -20 dBm at rates of over 1 Gb/s have been successfully detected and transmitted through the circuit to the output terminals.