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Measured dark current densities of 3 mm diameter and diodes.
Band diagram of (top) and (bottom) Ge/Si heterojunctions. Interface states were not taken into account. is the distance from the surface.
Measured external quantum efficiency of 3 mm diameter and diodes at 0 V bias. The inset shows the measured external quantum efficiency at 1550 nm of a 3 mm diameter diode as a function of bias.
EBIC observation of (left) and (right) Ge/Si heterojunction photodiodes. The black region inside the top ring contact in the diode indicates poor collection of generated carriers, with a signal level comparable to noise. The EBIC image was taken with a VEGA Tescan at an acceleration voltage of 30 kV.
Summary of different growth techniques used to grow Ge layer for vertical incidence Ge/Si photodectors (presented in Table II ). Corresponding growth conditions, characteristics, and results of the grown layers are indicated. LT and HT stand for low and high temperatures, respectively, UHVCVD for ultra high vacuum chemical vapor deposition, MBE for molecular-beam epitaxy, RPCVD for reduced-pressure chemical vapor deposition, and CMP for chemical mechanical polishing. In the LEPECVD case the two growth temperatures correspond to the undoped Ge layer and highly doped top Ge layer growth temperatures, respectively.
Summary of low dark-current vertical incidence Ge/Si photodectors found in literature and whose growth conditions are presented in Table I . The dark current density is for an applied bias of −1 V.
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