CARRIER LIFETIME VS. ION-IMPLANTATION DOSE IN SILICON ON SAPPHIRE.

Abstract

Measurements of the carrier lifetimes of a systematic series of SOS (silicon on sapphire) samples with increasing amounts of ion implantation are presented. The samples consist of 0. 5- mu m SOS wafers that were implanted with O** plus ions of doses ranging from 1. 0 multiplied by 10**1 **2 /cm**2 to 7. 5 multiplied by 10**1 **5 /cm**2 at 200 keV (and 100 keV in some cases). The carrier lifetimes are measured by time-resolved reflectivity and transmission measurements following excitation with femtosecond optical pulses. The variation of lifetime with implantation dosage saturates at a level 3. 0 multiplied by 10**1 **4 /cm**2 . Above this dose, the lifetime reaches a limit of 600-700 fs. Possible interpretations of the lack of dependence on ion-implantation level include saturation of effective trap densities and hot carrier relaxation.