Overgrowth on InP corrugations for 1.55 μm DFB LDs by reduction of carrier gas flow in LPMOCVD

Abstract

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 20 l/min, which was a typical growth and system-recommended condition, to 2 l/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 μm operating wavelength showed a threshold current of 12 mA (36 mA) and slope efficiency of 0.32 mW/mA (0.22 mW/mA) at 25°C (100°C). A side mode suppression ratio (SMSR) of 50 dB was obtained within the range of temperature, 25–85°C, and an injection current range of 40–200 mA.