Picosecond photodetectors fabricated on low temperature GaAs

GaAs metal-semiconductor-metal photodiodes fabricated on GaAs grown at low substrate temperatures (200 degree C) have been investigated in the time domain by electro-optic sampling. It could be shown, that these diodes have a faster response and a considerably reduced long time tail. They can be used at larger bias than comparable diodes produced on GaAs grown at 700 degree C. Temperature dependent measurements show, that the tail can be described by hopping conductivity and disappears below 50 K.