Abstract-Strong terahertz response in quantum well photodetector based on intradonor transition by magnetic field

AIP Advances

C. H. Yu, Lin Li, Teng Fei Xu,   Bo Zhang, X. D. Luo,  Wei. Lu,

Schematic of THz detection in GaAs/AlGaAs THz QWP based on IDTs in AlGaAs barriers under magnetic field. Step ①: ISBT in GaAs wells, ②: Landau quantization and shift of LL ε0,0 with magnetic field in GaAs wells, ③: electron transfer from LL ε0,0 in GaAs wells to the 1s donor ground state in AlGaAs barriers after magnetic field reaches its threshold Bt, ④: IDT in AlGaAs barriers, ⑤: thermal phonon absorptions. PTI is a two-step process including both step ④ and ⑤. εe means higher donor states in AlGaAs barriers, such as 2p+, (210) and (310) observed in measurement. The figure is not drawn to scale.

https://aip.scitation.org/doi/abs/10.1063/1.5051203

We report on spectral investigation of photocurrent of a nonconventional GaAs/AlGaAs quantum well photodetector (QWP) which realizes a response to terahertz (THz) radiation by intradonor transitions (IDTs) in AlGaAs barriers rather than typical intersubband transitions (ISBTs) in GaAs wells. The photodetector shows dramatically enhanced photocurrent intensity and THz response when under a perpendicular magnetic field. This magnetic field helps to improve the absorption quantum efficiency, remove the restriction of the polarization selection rule, and extract high density electrons from two-dimensional electron gas in GaAs wells after electrons transfer into AlGaAs barriers. The effect of the magnetic field on the peak intensity and the linewidth of the photocurrent peak responses is exploited to distinguish IDT and ISBT and to identify the crucial role of electron transfer in THz detection in QWP. This work is useful for exploring detection strategy and technology for high responsivity THz photodetector.