Tunneling dynamics and transport in MBE-grown GaAs/AlGaAs asymmetric double quantum wells investigated via photoluminescence and terahertz time-domain spectroscopy.

We study the transport of photogenerated carriers in molecular beam epitaxy (MBE)-grown gallium arsenide/aluminum gallium arsenide (GaAs/AlGaAs) coupled (CDQW) and uncoupled (UDQW) double quantum wells. Photoluminescence (PL) spectroscopy was used to investigate the optical properties and establish differences in the tunneling properties between the CDQW and UDQW. Terahertz time-domain spectroscopy (THz-TDS) measurements have shown that the emissions from the CDQW and UDQW were 57 % and 31 % of the THz emission of p-InAs, 800 nm excitation wavelength. The higher THz emission from the CDQW is attributed to the tunneling of electrons from the NW to the WW leading to a larger dipole moment. Furthermore, excitation wavelength-dependent THz-TDS measurements have shown that when the NW is not photoexcited, high-frequency components appear in the frequency spectra. These results provide insights on the possible development of DQWs as THz optoelectronic devices. It also demonstrates the application of THz-TDS in investigating tunneling dynamics in DQWs in conjunction with established optical characterization techniques, such as PL spectroscopy. [ABSTRACT FROM AUTHOR]