InGaAs/InGaAsP Quantum-Well Engineering for Multiple Regrowth MOVPE Process

Abstract

For the heterogeneous integration of several layer structures for absorber, gain and passive waveguide sections in a monolithically-integrated mode locked laser diode, the bandgap of the absorber section has to be matched to the emission wavelength of the gain section. Because of the use of a multiple regrowth process for optical butt-coupling, the first grown multiple quantum-well gain material undergoes a quantum-well intermixing process, resulting in a blue shift of the emitting optical wavelength. Experimental results show, that the blue shift is dependent on the process details and cannot be investigated by simple thermal cycling of unprocessed quantum well-structures. With the introduction of an effective quantum-well width computed from the emission wavelength we found a linear relationship between the effective quantum well width shrinkage and the cumulated regrowth heating time of 8.3Å/h at a growth temperature of 630°C. Therefore knowing the cumulated regrowth time for a laser fabrication, we could successfully design the initial quantum well thickness that yields the targeted emitting wavelength and excellent matching to the absorber bandedge.