Electrical characteristics and deep-level transient spectroscopy of a Ge0.873Si0.104Sn0.023 photodiode grown by ultra-high vacuum chemical vapor deposition on a p++ Ge platform are investigated. The photodiode shows good rectifying I-V characteristics, and the dark current exhibits an activation energy of E-dc = 0.43 eV at high temperature while the reverse bias leakage current in the film is low but increases with temperature. Capacitance-voltage measurements show the diode has a built-in potential of 0.37 V at 300 K; the depth profile obtained from capacitance-voltage measurements is in agreement with secondary ion mass spectrometry analysis reported previously. Deep level transient spectroscopy shows two electron traps at similar to 100 K and at similar to 165 K with energy levels at similar to 0.09 eV and similar to 0.36 eV from the conduction band, respectively; and at least one hole trap at similar to 275 K with energy level at similar to 0.61 eV from the valence band (similar to 0.33 eV from the conduction band) existing in the device.