Bound excitons at doubly ionizable acceptors in GaSb

Experimental results on excitons bound to neutral doubly ionizable acceptors are presented and discussed. In particular, the bound-exciton emission was investigated as a function of the concentration of the natural acceptor in GaSb and as a function of uniaxial stress. The final state after decay of the bound exciton is split by the $\mathrm{jj}$ coupling of the holes. From the stress dependence we determine the values of the three different deformation-potential constants that must be assumed for the ionized acceptor, neutral acceptor, and the bound-exciton states, i.e., one-, two-, and three-hole states, respectively. The reduction factors for the uniaxial-deformation-potential constants of the bound holes were deduced from simultaneous measurement of the free-exciton reflection and the photoluminescence under uniaxial stress. These factors show a strong dependence on the binding energy of the bound holes. The magnetic field data can be interpreted completely with this model.