Metamorphic growth of 1.25-1.29mum InGaAs quantum well lasers on GaAs by molecular beam epitaxy

We demonstrate 1.25-1.29mum metamorphic laser diodes grown on GaAs by molecular beam epitaxy (MBE) using an alloy-graded buffer layer (GBL). Use of Be in the GBL is effective to reduce surface/interface roughness and improves optical quality. The RMS surface roughness of the optimized metamorphic laser is only two atomic monolayers for 1X1mum2. Cross-sectional transmission electron microscopy (TEM) images confirm that most dislocations are blocked in the GBL. Ridge waveguide lasers with 4mum wide ridge were fabricated and characterized. The average threshold current under the pulsed excitation is in 170-200mA for a cavity length of 0.9-1.5mm. This value can be further reduced to about 100mA by high-reflectivity coating. Lasers can work in an ambient temperature up to at least 50 deg C.