Optimising 1550 nm InGaAsP strain compensated MQW lasers close to the miscibility gap

Abstract

Fabry Perot 1550 nm sources are required for a number of high volume short haul applications, and an optimised device design is sought which is suitable for wide temperature range operation. Strain compensated multi-quantum well lasers with between five and 11 wells were produced using MOCVD with ~1% compressive strain in the wells, and ~1% tensile strain in the barriers. Electrical, optical, X-ray and TEM studies were used to determine the material properties. Although RT-PL measurements indicated good material quality for all wafers, significant degradation in device properties was observed for larger well numbers. TEM studies are presented which show the degradation to be due to the onset of ‘wavy layer’ growth, which is also responsible for a broadening of the satellite peaks in the X-ray rocking curves for the material. Although wavy layer effects constrain the matrix, high quality devices were produced with low thresholds, high output powers, and wide temperature range operation.