Self-heating is a crucial effect in integrated nanophotonic devices regarding their power consumption. In this work, we employ coupled 3D thermo-electrical simulations to gain insight into the thermal behavior related to traps in a monolithic InP-InGaAs-InP pin-diode fabricated at IBM-Research Zurich. From transport study, two types of defects are found to be very likely present in the studied device: (i) positive oxide charges close to the interface between III-V materials and top oxide layer and (ii) electron-type traps at the p-InP/i-InGaAs interface. Thermal simulations show that the presence of electron-type traps at the p/i interface enhances the self-heating in the device.