ABSORPTION-COEFFICIENT AND EXCITON OSCILLATOR-STRENGTHS IN INGAAS INPMULTIQUANTUM WELLS/

The excitonic properties of InGaAs/InP multi-quantum-well systems grow n by chemical beam epitaxy have been investigated with absorption meas urements in the temperature range 8-300 K and in the spectral region 0 .775-1.550 eV. In this region, the excitonic resonances corresponding to n=1, n=2 interband transitions, and the steplike behaviour of the t wo-dimensional density of states have been clearly observed. By fittin g the lineshape of the excitonic features with Gaussian functions the most noteworthy parameters are discussed. The energy position of the p eak changes as a function of temperature, according to the relation kn own for the InGaAs energy gap. Moreover, the full width at half maximu m is deduced and is discussed in terms of an intrinsic contribution pl us a thermal broadening due to the interaction with LO phonons. The in tegrated area of the excitonic peak examined seems to be temperature i ndependent. On the other hand, the integrated area decreases when the well width increases, because of the shrinkage of the Is exciton wave function. A ratio of the oscillator strengths related to light, and he avy hole excitons equal to 0.6 has been determined, in accordance with the theoretical prediction.