Carrier dynamics in Er,O-codoped GaAs revealed by time-resolved terahertz emission measurements

Transient carrier dynamics in Er,O-codoped GaAs (GaAs:Er,O) have been investigated by terahertz (THz) emission from the sample surface. The THz radiation from GaAs:Er,O was observed under 800 nm optical excitation and depended on Er concentration. The radiated THz amplitude decreased and the decay time of transient photocurrent became long as the Er concentration was increased. GaAs:Er,O with the highest Er concentration of 8.7times10¹⁸ cm^-3 showed the decay time of 0.86 ps which was longer than that of 0.37 ps in an undoped GaAs epitaxial layer. These results were understood by electron scattering due to the codoping of Er and O.