HOLE INTERSUBBAND RELAXATION IN CDTE CDMNTE QUANTUM-WELLS/

We report a direct measurement of the hole relaxation time in undoped CdTe/CdMnTe quantum wells. The internal piezoelectric field in a (111) -grown structure is screened by e(1)h(1) and e(1)h(2) excitons with di fferent efficiency. Thus, the temporal evolution of the screened field , as monitored by the e(1)h(1) exciton energy in a pump-probe transmis sion experiment, allows the determination of the e(1)h(2) - e(1)h(1) r elaxation time. We obtained a relaxation time of 15+/-5 ps for a split ting of 15 meV, smaller than the longitudinal-optical (LO) phonon ener gy. Deformation-potential scattering is too slow to explain this relax ation time which we attribute to hole-hole scattering and LO-phonon em ission by e(1)h(2) excitons acquiring enough kinetic energy. (C) 1997 American Institute of Physics.