Calculation of optical absorption associated with indirect transitions in siliconnhyphen;ihyphen;phyphen;istructures

摘要

Indirect transitions in siliconnhyphen;ihyphen;phyphen;istructures are investigated theoretically. A method is used in which these structures are characterized by their internal electric fields, which change the absorption in a Franzndash;Keldyshhyphen;like manner. Our calculations, in which the influence of excitons is included, are based upon the effectivehyphen;mass approximation. The conclusions are that the absorption only increases in an energy region for which the absorption is very small in the first place. It is further shown that excitonic effects are very important in this geometry, in spite of the strong internal electric fields, or, equivalently, in spite of the large spatial separation of the carriers.