AbstractThe improved thermal stability of InGaAlAs‐based lasers compared with InGaAs‐based lasers for 1.5 μm operation is investigated using a combination of low temperature and high pressure techniques. The results indicate that the improved performance of InGaAlAs‐based devices is due to a reduction in the contribution of the non‐radiative Auger recombination current, IAug, to the total threshold current, Ith, in the InGaAlAs devices. This is due to the higher conduction band offset made possible with the InGaAlAs system which results in a lower hole density in the quantum wells at threshold. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)