Wide tunability and electron transfer in GaAs/AlGaAs quantum well photodetector by magnetic field

One strategy for terahertz (THz) detection in GaAs/AlGaAs quantum well photodetectors under the magnetic field is reported. The THz detection begins to operate after the normally empty hydrogenic donor ground states in the AlGaAs barriers become populated by electrons transferred from the GaAs wells. Through the Landau quantization arising from a perpendicular magnetic field, we achieved the electron transfer from subband Landau levels in the GaAs wells at liquid helium temperature when the magnetic field reaches a certain threshold. One detector based on this strategy exhibited a dramatic range of frequency tunability of 3.20–6.13 THz. Our photothermal ionization spectroscopy measurements show quantitative agreement with the theoretical calculation of intradonor transition energies, verifying the origin of the strongly enhanced frequency tunability from the Zeeman behavior of transferred electrons in the AlGaAs barriers. This finding is useful for exploring magneto-optical effects and realization of wide tunability in THz photodetectors.