Credit: Light: Science & Applications
a, Transient THz dynamics of Te/Ge and Ge/Te heterojunctions with 800 nm excitation wavelength. b, Left: Calculated space distribution of the differential charge density for different materials on substrate. The color blue (yellow) denotes electron depletion (accumulation). Right: Schematic substrate-induced electric fields and charge transfer in heterojunctions of Te/Ge (upper) and Ge/Te (lower), respectively.