Abstract
The threshold current of InGaAsP–InP double hetetostructure lasers has been investigated through measurements of the temperature dependence of carrier lifetime and radiative efficiency. Both the carrier lifetime and the radiative efficiency decrease noticeably above the break point temperature as observed in the Ith vs. T relation. The decrease of the carrier lifetime is explained by considering additional non-radiative recombination centers with 0.3 eV activation energy. The origin of this center is also discussed.