The quantum efficiency and reliability of III-V semiconductor-based light emitters can be significantly degraded by nonradiative recombination resulting from the presence of harmful surface states at the mesa sidewalls of the devices. Specifically, surface states are expected to substantially affect the possibility to observe electroluminescent cooling (ELC) in III-As light-emitting diodes (LEDs). Here, we confirm the existence of significant surface currents by exploring the effect of ammonium polysulfide [(NH4)(2)S-x] surface passivation on a GaInP/GaAs heterojunction double diode structure (DDS) designed to study the feasibility of ELC. The DDS consists of an LED and a photodiode (PD) within a single device structure, enabling easy monitoring of the photon-mediated thermal energy transport between the LED and the PD, and eliminating challenges associated with light extraction. Our results show that the surface passivation can improve the internal quantum efficiency of the LEDs by more than 10% points under optimal bias conditions.