We investigate the influence of Rh-doping on electrical properties of InP and InGaAs. Deep level transient spectroscopy carried out on Rh-doped as well as undoped reference samples reveals a single Rh-related deep level in both semiconductors. While a Rh-related electron trap in InGaAs is situated at EC-0.38eV a Rh-related hole trap is found to exist in InP approximately 0.73 eV above the valence band edge. The internal reference rule for 3d transition metal deep levels is found to be valid for these 4d transition metal levels: their energy is constant across the InGaAs/InP heterojunction. We conclude these levels to be the single acceptor states of Rh substitutionally incorporated on cation sites.