1-picosecond InGaAs Photodetector For Operation At 1300-1600 Nm

THE OBJECTIVE OF THIS PROPOSAL IS TO DEVELOP A 1-PICOSECOND MONOLITHICALLY INTEGRATABLE PHOTODETECTOR WITH 0.2 A/W RESPONSIVITY FOR ULTIMATE USE AT 1600 NM. THE DETECTOR WILL RELY ON THE INTRISIC CARRIER LIFETIME OF THE SEMICONDUCTOR FOR ITS SPEED AND ON SUBMICROMETER-SPACED INTERDIGITATED FINGER ELECTRODES FOR ITS SENSITIVITY. ONE SEMICONDUCTOR ALREADY DEVELOPED FOR SHORTER WAVELENGTH APPLICATIONS IS LOW-TEMPERATURE-MBE-GROWN GaAs (LT-GaAs). THIS MATERIAL IS RICH IN ARSENIC DEEP-LEVEL TRAPPING CENTERS, RESULTING IN ITS SUBPICOSECOND CARRIER LIFETIME. USING LT-GaAs, WE HAVE RECENTLY DEVELOPED A PHOTODETECTOR, SENSITIVE OUT TO 800 NM, THAT HAS A 1.2 PICOSECOND RESPONSE TIME AND 0.1 A/W RESPONSIVITY. THIS IS THE FASTEST PHOTODETECTOR IN THE WORLD. WE NOW WISH TO APPLY THE TECHNIQUE OF LOW-TEMPERATUREMBE TO InGaAs MATERIAL FOR DEVELOPMENT OF PICOSECOND PHOTODETECTORS SENSITIVE OUT TO 1600 NM. DURING THIS PHASE I PROGRAM, WE WILL INVESTIGATE THE LOW-TEMPERATURE GROWTH OF InGaAs ON GaAs. WE HAVE FOUND THAT BY GROWING A LATTICE-MISMATCHED LAYER, WE CAN OBTAIN HIGH-RESISTIVITY MATERIAL WITH NO LOSS IN SENSITIVITY. WE WILL STUDY THE EPILAYER SYSTEM IN TERMS ITS LIFETIME, MOBILITY, DARK CURRENT, AND VOLTAGE HOLD-OFF, AS FUNCTIONS OF THE GROWTH-AND POST-ENNEALING TEMPERATURES. WE WILL THEN FABRICATE PHOTODETECTORS AND CHARACTERIZE USING PICOSECOND ELECTRO-OPTIC SAMPLING.