NARROW-GATE IN0.53GA0.47AS JUNCTION FIELD-EFFECT TRANSISTORS AS TUNABLE RESISTORS FOR LONG-WAVELENGTH INTEGRATED OPTICAL RECEIVERS

We have fabricated In0.53Ga0.47 As junction field-effect transistors (JFET’s) for use as active feedback resistors in integrated transimpedance photoreceivers. Transistors using both air-bridge and non-air-bridge technologies are described. By varying the gate-to-source voltage (VGS), the output resistance is continuously tuned between 3 and 40 k? with a drain-to-source shunt capacitance of less than 10 fF. The temperature coefficient of output resistance is between -5 and -20 ?/°C (for VGS less than the pinch-off voltage). The combination of large resistance and low shunt capacitance can result in high receiver sensitivity without sacrificing amplifier dynamic range. The feedback FET’s were fabricated adjacent to 1.8-?m gate JFET’s with transconductances of 110 mS/mm and gate-to-source capacitances of 1.3 pF/mm. The compatibility of these two transistor structures suggests that an integrated preamplifier with dynamically tunable bandwidth can be realized using InP-based materials. © 1990 IEEE