Laser spectroscopy of individual quantum dots charged with a single hole
  We characterize the positively charged exciton (X1+) in single InGaAs quantum dots using resonant laser spectroscopy. Three samples with different dopant species (Be or C as acceptors, Si as a donor) are compared. The p-doped samples exhibit larger inhomogeneous broadening (x3) and smaller absorption contrast (x10) than the n-doped sample. For X1+ in the Be-doped sample, a dot dependent non-linear Fano effect is observed, demonstrating coupling to degenerate continuum states. However, for the C-doped sample the X1+ lineshape and saturation broadening follows isolated atomic transition behaviour. This C-doped device structure is useful for single hole spin initialization, manipulation, and measurement. 
B. D. Gerardot, R. J. Barbour, D. Brunner, P. A. Dalgarno, A.   Badolato, N. Stoltz, P. M. Petroff, J. Houel and R. J. Warburton
cond-mat.mes-hall quant-ph