OPTICAL-PROPERTIES OF GE SELF-ORGANIZED QUANTUM DOTS IN SI

Small-size, high-density, and vertical-ordering Ge quantum dots are ob served in strained Si/Ge short-period superlattices grown on Si(001) a t low growth temperature by molecular-beam epitaxy. The photoluminesce nce (PL) peak position, the strong PL at room temperature, and the hig h exciton binding energy suggest an indirect-to-direct conversion of t he Ge quantum dots. This conversion is in good agreement with the theo retical prediction. The characteristic of absorption directly indicate s this conversion. The tunneling of carriers between these quantum dot s is also observed. [S0163-1829(98)03515-2].