EXCITONS IN SPATIALLY SEPARATED ELECTRON-HOLE SYSTEMS - A QUANTUM MONTE-CARLO STUDY

Variational and diffusion quantum Monte Carlo simulations of excitons in the type-II semiconductor quantum well system In1-xGaxAs/GaSb1-yAsy are performed for a wide range of composition (0,0) less than or equa l to(x,y)less than or equal to(0.62,0.64) and well width 25 Angstrom l ess than or equal to L less than or equal to 200 Angstrom. The exciton binding energy is found to increase with the decrease of the layer th ickness and with the increase of the composition. The calculated resul ts suggest that a novel semiconductor-excitonic insulator (Bose conden sate)-semimetal transition should be observable in this system. (C) 19 95 American Institute of Physics.