The curves of the minority carrier lifetime versus current are measured in InGaAsP-InP double heterostructure LED's. To analyze the measured data the carrier recombination rate R(tot) versus the minority carrier concentration n are calculated. The following recombination processes are considered to explain the measured data: radiative, Auger, on heterointerfaces and/or on recombination centres. The radiative recombination rate R(rad) versus n curves are confirmed to be parabolic. A simple analytical formula for the radiative recombination rate coefficient B(n) is derived.