Chemical beam epitaxy of GaInAsP for long-wavelength lasers

The precise control of growth parameters in chemical beam epitaxy (CBE) is essential for high-quality photonic devices and monolithic integration in OEICs. We find a very narrow growth window suitable for high-quality GaInAsP. We observe a strong dependence of crystal quality from the V/III ratio at a growth temperature of 543°C. For GaInAsP with a band gap of 0.95 eV (λ = 1.3 μm) a miscibility gap occurs at this temperature. The material quality is demonstrated by very narrow photoluminescence linewidths of 3-5 meV at 4.2 K for (GaIn)(AsP) layers of varying compositions. Laser diodes grown under the optimised conditions without growth interruptions show very low threshold current densities of 62 A cm^-2 per QW for 10 QWs. Internal losses can be reduced by using tensile-strained barriers.