Influence of mask design on the growth of InGaAs/InAlAs quantum wells on patterned substrates

The influence of mask geometry on growth enhancement and alloy composition was investigated for InGaAs/InAlAs multiple quantum well structures grown on patterned InP (100) substrates by low pressure metalorganic vapor phase epitaxy. The masks used have a window 20 μm wide and width varying between 5 and 75 μm. Two different regimes have been observed. For masks with width smaller than 40 μm both growth enhancement and alloy composition influence the lowest optical transition energy, while for masks wider than 50 μm, alloy composition remains stable and selectivity is essentially due to growth enhancement. With the results obtained together with calculations of the Schrödinger equation within the effective mass approximation, one concludes that, with proper mask design, it is possible to obtain an array of several modulators with slightly different operation wavelengths which are all polarization independent. In addition, the waveguiding characteristics of a modulator sample selectively grown was analysed by near field experiments. Comparing the results with a sample conventionally grown, one concludes that the selective growth technique essentially does not influence the waveguiding properties.