OPTICAL CHARACTERIZATIONS OF (111) ORIENTED INGAAS/INALAS STRAINED QUANTUM-WELLS GROWN ON INP SUBSTRATES

Strained InGaAs/InAlAs quantum wells with compressively or tensilely strained InGaAs layers were successfully grown on slightly misoriented (111) B InP substrates. Optical properties were systematically studied from comparisons of theoretical and experimental data. The transmission spectra measured on both the (111) and the (100) oriented strained quantum wells showed excitonic peaks even at room temperature, which revealed the high quality of these quantum wells. The peak positions for the (111) oriented quantum wells corresponded well to the calculated excitonic transition energies only when growth orientation dependence of material parameters was taken into account. In the photoluminescence measurements with various excitation intensity, it was found that only the peak from compressively strained (111) InGaAs quantum wells blue-shifted as the excitation intensity increased. This implies the screening of the internal electric field, that is a piezo-electric field, by photogenerated carriers and a consequent decrease in the quantum confined Stark shift. These results provide evidence for the existence of a built-in electric field in the strained InGaAs/InAlAs quantum wells. These strained quantum wells grown along the (111) direction are found to be promising for the realization of optical bistable devices and optical switches in the long wavelength region by the use of the internal electric field.