QUANTUM MONTE-CARLO STUDY OF POLYEXCITONS IN SEMICONDUCTORS

A variational Monte Carlo method was used to calculate the binding energies and ground-state wave functions of two-, three-, and four-exciton complexes in indirect-band-gap semiconductors within the spherical-effective-mass approximation. The results for two-exciton complexes (biexcitons) have been compared with those of Green's-function Monte Carlo calculations which produce exact ground-state energies within statistical error; the variational results recover about 90% of the binding energy of these systems. For three- and four-exciton complexes in Si, we predict that the binding energy with respect to the smaller complex with one less exciton is about 2.2 meV, in fair agreement with the experimental value of 2.5 meV. © 1990 The American Physical Society.