Quantum indistinguishability effects of confined polyexcitons

We report experimental evidence for the existence of confined polyexcitons in strain-relaxed epitaxial SiGe layers by means of low-temperature photolu minescence. The number of excitons, n, up to four in a polyexciton is confi rmed. Our data clearly show that only one type of polyexciton is confined i n potential wells generated by lower band-gap regions in SiGe layers due to alloy fluctuations. The radiative annihilation of a polyexciton with a giv en n produces n - 1 photons and a single exciton left behind. The most stri king fact is that confined polyexcitons having n > 2 do not decay to polyex citons having n - 1. These observations can be explained by the quantum eff ect of indistinguishability of polyexcitons which possess either zero or in tegral spin. This effect is enhanced in a confined well since confined poly excitons interact strongly among themselves in a limited spatial region. Ou r observations are important to understand the unique properties of a few q uantum particles in a confined region. [S0163-1829(99)03832-1].