Design, growth and performance of different QW structures for improved 1300 nm InGaAsP lasers

We have investigated the material quality of three alternative InGaAsP 1.3 mu m wavelength multiple quantum well structures with strained wells, fabri cated by low pressure metal organic vapour phase epitaxy. The designs have radically different compositions but similar calculated properties concerni ng gain, carrier distribution, laser threshold and optical output power. Th e structures considered all employ compressively strained wells and have co nstant-As, constant-Ga or InAsP-InGaAsP materials in wells and barriers. Gr owth conditions were optimised for each design. Evaluation of the constant- As multiple quantum well (MQW) resulted in poor X-ray diffraction (XRD) and photoluminescence (PL) response. The InAsP MQW exhibited clearly defined X RD-satellites but as the As-content was increased to reach 1.3 mu m, PL pro perties degraded severely. The constant-Ga MQW indicated superior material quality with excellent PL and XRD properties. Fabricated lasers with up to 12 periods and lattice matched barriers. showed internal efficiency values above 95%, internal losses below 10 cm(-1), threshold densities as low as 6 0 A cm(-2)/well and temperature constant, T-0, values as high as 79 K in th e temperature range 20-80 degrees C. The constant-Ga structure allows a var iable barrier height, strain compensation and simultaneously avoids the pro blem with growth undulation and interdiffusion, typically encountered for t he InAsP and constant-As cases and should therefore be an excellent candida te for active layers in 1.3 mu m lasers. (C) 1998 Elsevier Science B.V. All rights reserved.