AlGaAs VSCELs grown on thin 150 mm germanium substrates

Abstract To reduce material usage and minimise device cost the use of reduced substrate thickness is considered in high volume vertical-cavity surface-emitting laser (VCSEL) manufacturing. For large-diameter VCSEL wafers, germanium (Ge) is emerging as an alternative substrate solution. In this work, VCSEL structures designed for 940 nm emission are grown by metal–organic vapour-phase epitaxy on 150 mm (6 inch) germanium substrates of thickness 675, 450 and 225 µ m. Using on-wafer testing of fabricated devices, threshold current density, differential resistance, and emission wavelength are compared across the three substrate thicknesses, with results demonstrated for the first time on a Ge wafer thickness of 225 µ m. These results underline the potential of thin Ge substrates for reduced material usage in VCSEL manufacturing.