Abstract
Optically excited THz-radiation from ten molecular-beam epitaxy (MBE)-grown strained multiple quantum wells (MQWs) on a (100)-oriented semi-insulating GaAs substrate is studied in a 1-T magnetic field. Wavelength-dependent THz-radiation clearly exhibits a resonance behavior at the excitation wavelength near 830 nm, the peak wavelength of photoluminescence (PL). We also observe and explain an emission spectrum from the MQW with slightly enhanced higher-frequency components compared to that of bulk GaAs. In the thin MQW sample, the THz emission is still significant, This indicates the possibility of designing MQWs as efficient THz emitters in the future.