OPTICAL PHONONS IN STRAINED SINGLE INAS INP QUANTUM-WELLS - A RAMAN-STUDY/

Confined and interface optical phonons are observed in InAs/InP single quantum wells. Under InAs E1-gap resonant excitation, confined longit udinal-optical phonons of A1 and B2 symmetries are observed in both z( x, x)zBAR and z(x, y)zBAR polarization configurations. This relaxation of the selection rules is analyzed in terms of impurity-induced scatt ering. The enhancement of the intensity of the confined modes under re sonant excitation indicates that the scattering involves E1-gap excito ns strongly confined in the InAs well. Both InAs-like and InP-like int erface phonons are observed. Their energy positions are well explained by an electrostatic continuum model, assuming that two distinct mecha nisms contribute to the presence of nonzero wave-vector modes. The fir st involves impurity-induced scattering and the second is attributed t o a modulation of the InAs well thickness.