Transport in Heterostructures and Devices in Microwave and Millimeter-WaveRegimes

摘要

Transport phenomena has been studied in semiconductors and superconductormaterials, and devices, using ultrafast optical and electrical signals. Femtosecond optical absorption spectroscopy has been used to study the carrier dynamics in low-temperature epitaxially grown (LT) Gallium Arsenide. Optical techniques have also been used to observe for the first time the ballistic acceleration of electrons from the bandedge in a GaAs quantum well and the domain formation in superlattices as well as excitonic transport in quantum wells. Using LT GaAs ultrafast electrical signals, less than 1 ps in duration, have been produced with amplitude up to 1 KV. These pulses have a frequency spectrum extending to 1 THz and have been used to study the physics of semiconductors and semiconductor devices in the high-field and high-frequency regime. Using LT GaAs photoconductive switches, and in conjunction with the electrooptic sampling we built an electro-optic analyzer capable of extracting S-parameters of active devices, up to 100 GHz. These techniques have been applied for the measurement of the fastest photoconductive response times of GaAs and In-GaAs epitaxially grown at 200 C.