We describe reproducible and uniform overgrowth on InP corrugations to fabricate DFB LDs by reduction of carrier gas in an LPMOCVD system. The reduction of carrier gas from 201/min, which was a typical growth and system-recommended condition, to 21/min during heat-up time enabled the growth of an InGaAsP layer on InP corrugations for any heat-up condition including heat-up time and heat-up ambient. The TEM image showed abrupt interfaces in the MQW layer and a non-defective interface between the InGaAsP layer and the InP corrugations. This study demonstrated the variation of residual grating depth with changing the heat-up time while maintaining a specific gas ambient. The SEM and microscopic images showed the effect of reducing the carrier gas flow. A fabricated DFB laser diode with 1.55 mum operating wavelength showed a threshold current of 12mA (36 mA) and slope efficiency of 0.32mW/mA (0.22 mW/mA) at 25degreesC (100degreesC). Aside mode suppression ratio (SMSR) of 50 dB was obtained within the range of temperature, 25-85degreesC, and an injection current range of 40-200 mA. (C) 2003 Elsevier B.V. All rights reserved.