On the nature of centers responsible for the spin-dependent recombination in Si and Ge

Abstract

We have previously observed /1, 2/ photoinduced EPR signals (PS EPR) in Si and Ge monocrystals. It was shown, on the basis of the spin-dependent recombination model /3/, that the Q value registered as PS EPR change of the resonator is connected with the resonance change of photoconductivitv. If the injection level is constant the intensity of PS EPR (I) with a single recombination channel does not depend on the concentration of paramagnetic recombination centers /2/. I With several recombination channels being available, either dependent on the spin polarization o r independent, the change of I will be connected with the variation of the relative contribution of the spin-dependent component of recombination to the total recombination rate (6). F o r example, the &crease of I due to active surface treatment can be connected not only with the reduction of the paramagnetic center concentration, but with the increase of the number of non-paramagnetic recombination centers. It is known /4/ that one can distinguish two surface recombination rate components at the real surface of such semiconductors as Si and Ge. The first being strong dependent on the surface potential (bell shape component Sb, and the second weakly dependent on the potential Sc /4/). To explain the problem which component is connected with the spin polarization, we have studied the influence of various active surface treatments on the intensity of PS EPR. The experiments were made with Si monocrystals of p-and n-type ( 9 = 3000 to 1000 Qcm) and Ge monocrystals of p-type ( 8 = 20 to 30 Rcm). A l l the Samples were etched either in C P o r KOH. A s shown in Fit. 1 the intensity of PS EPR (curves 1 , 2 ) decreases when Si -6 monocrystals in C P etched a r e heated in vacuum (P ~. l 0 ence of oxvgen (P * 50 Torr). Signals a r e absent on samples etched in KOH, Torr) o r in the pres-