IMPORTANCE OF METALORGANIC VAPOR-PHASE EPITAXY GROWTH-CONDITIONS FOR THE FABRICATION OF GAINASP STRAINED-QUANTUM-WELL LASERS

GaInAsP/GaInAsP multi quantum well (MQW) structures with 1% compressive strain in the wells and a bandgap wavelength of 1.55 mu m have been grown by low-pressure metalorganic vapor phase epitaxy (LP-MOVPE). Photoluminescence (PL) measurements at 300 and 4 K together with X-ray diffraction analysis reveal a strong dependency of the material quality on the MOVPE growth conditions. The photoluminescence intensity could be increased by more than a factor of 3 by optimizing reactor pressure and temperature. Under properly chosen pressure and temperature in the reactor, we found a greatly reduced sensitivity of the material quality to other parameters such as growth interruptions or barrier composition. When utilizing strain-compensating barriers, the number of strained quantum wells could be increased up to 32, without any indication for material degradation due to strain relaxation. Utilizing those findings, distributed feedback (DFB) laser structures employing 8 compressive strained wells with lattice-matched as well as strain-compensating barriers have been grown. The processed lasers showed excellent static and high-frequency characteristics with threshold currents as low as 3.3 mA and a 3dB modulation frequency of 21.7 GHz, which is among the highest values ever reported for DFB lasers.