M. Kemerink et al., MAGNETOOPTICAL STUDY ON EXCITON SCREENING IN P-TYPE ALXGA1-XAS INYGA1-YAS QUANTUM-WELLS/, Physical review. B, Condensed matter, 56(8), 1997, pp. 4853-4862
We have studied exciton unbinding in empty and p-doped quantum wells,
using magnetophotoluminescence excitation measurements. The use of p-t
ype quantum wells allows us to discriminate unambiguously between exci
ton bleaching by Coulomb screening and by the Pauli exclusion principl
e. We found that the ground-state heavy-hole exciton, which experience
s both effects, is unbound at hole densities in the range (6-9) x 10(1
5) m(-2). In contrast, the ground-state light-hole and first excited h
eavy-hole excitons, which are only screened by the Coulomb interaction
, still have a finite binding energy at these densities. However, for
both bands, its Value is far below what is found in an undoped well. F
urthermore, we found a strong indication that, in p-doped wells, the e
xcitons of excited subbands are less efficiently screened than those o
f the Light-hole ground state, due to the lesser overlap of the screen
ing ground-state heavy holes with the excited subbands than with the g
round-state light holes.