Higher yield of 1.55 μm DFB lasers through MOVPE growth under N2 atmosphere with excellent homogeneity

In order to increase the utilizable wafer area for DFB laser production, metalorganic vapor phase epitaxy (MOVPE) under N2 as carrier gas has been applied for the first time to strain-compensated InGaAsP multi-quantum-well (MQW) structures on InP. Various InGaAs(P) layers and MQW structures were grown by low-pressure MOVPE in a horizontal reactor with substrate rotation using standard precursors. By replacing H2 by N2 the material homogeneity was considerably improved in all properties like wavelength, lattice mismatch and layer thickness. The role of the carrier gas is discussed. The standard deviation σ(λ) of the wavelength of bulk InGaAsP (λ=1.3 μm) 50-mm wafers was reduced from 4.0 nm (H2) to 0.63 nm (N2) and that of strain-compensated λ=1.55 μm laser structures with 10 QWs from 6.5 nm (H2) to 0.55 nm (N2). This increases the utilizable wafer area by a factor of six! This is one of the best homogeneity values reported so far for InGaAsP grown in any type of MOVPE reactor with any precursors. Details of the growth parameters and results are presented along with the characteristics of DFB laser arrays produced from these structures.