Fig. 4

Dark currents and photocurrent from Ge/GaAs UTC-PD with different device size conditions. (a) Dark current versus voltage characteristics for Ge/GaAs UTC-PD devices with varying diameters (5 µm to 8 µm) at different bias conditions. (b) Photocurrent versus voltage characteristics for Ge/GaAs UTC-PD devices with varying diameters (5 µm to 8 µm) at different bias conditions.