POSITRONIUM IN QUANTUM-WELL SEMICONDUCTOR STRUCTURES

The wave function proposed by Efros [Sov. Phys. Semicond. 20, 808 (1986)] for an exciton state of positronium Ps is used to calculate its annihilation characteristics in quantum-well semiconductor structures exhibiting strong anomalies. It is shown that in the case of a ''silicon'' quantum well the contribution of the intrinsic annihilation of para-Ps to the overall annihilation process is 6.5% (corresponding to the case where d much less than a; here, d is the width of a quantum well and a is the Bohr radius of Ps). These specific states of para-Ps may be observed in precision experiments at liquid-helium temperatures.