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 ${\mathit{E}}_1$-gap resonant excitation, confined longitudinal-optical phonons of ${\mathit{A}}_1$ and ${\mathit{B}}_2$ symmetries are observed in both z(x,x)z¯ and z(x,y)z¯ polarization configurations. This relaxation of the selection rules is analyzed in terms of impurity-induced scattering. The enhancement of the intensity of the confined modes under resonant excitation indicates that the scattering involves ${\mathit{E}}_1$-gap excitons strongly confined in the InAs well. Both InAs-like and InP-like interface phonons are observed. Their energy positions are well explained by an electrostatic continuum model, assuming that two distinct mechanisms contribute to the presence of nonzero wave-vector modes. The first involves impurity-induced scattering and the second is attributed to a modulation of the InAs well thickness.