Multiquantum barriers (MQBs) were introduced into 660 nm GaInP/AlInP lasers with superlattice confinement (SLC) layers, resulting in drastic improvements in lasing performance. Lowest threshold current densities (840 A/cm2) and highest room‐temperature values forT0(167 K) ever reported for 660–680 nm range lasers with bulk active layers were achieved. High‐temperature characteristics of the threshold current densities were measured in order to investigate the enhanced carrier confinement effect of MQBs and to estimate the excess nonradiative recombination current component. From the temperature dependence on the excess current density, the activation energiesE0of nonradiative processes were estimated to be 0.45 eV for MQB‐SLC lasers, and 0.26 eV for conventional SLC lasers without MQB. The increase ofE0demonstrates the enhanced heterobarrier effect by MQBs.