Majority- and minority-carrier lifetime in MOS structures

Abstract

The technique proposed by Goetzberger and Nicollian to determine carrier lifetime in MOS structures from admittance measurements in inversion, is reexamined. The interpretation of the experimental results is carried out in terms of a simplified equivalent circuit, which is topologically the same as that used by the preceding Authors, but differs for the expressions of some parameters appearing in it. The validity of the above equivalent circuit in inversion is demonstrated by comparing the frequency dependence of its admittance, both with the transmission line model, and with experimental results. Majority and minority carrier lifetime measurements are performed on n-type 〈100〉 and 〈111〉 oriented samples, oxidized both in the presence and in the absence of hydrochloric acid. It is shown that the addition of HCl to the oxygen-gas stream has determined a three-fold increase in the majority-carrier lifetime, and a sixty-fold one in the minority-carrier lifetime. The latter observation would indicate that HCl acts on the SRH centers by modifying their capture-cross section, rather than rendering them electrically inactive as assumed in earlier papers.