Identification of Trapping Effects and Ion Neutralization at the Insulator/Semiconductor Interface of MIS Structures from Dynamic Current–Voltage Characteristics of Ion Depolarization

Abstract

The manifestations of ion traps, ion neutralization, and minority carrier generation at the insulator/semiconductor interface (hereafter, interface for brevity) in MIS structures are judged from isothermal dependences of ion depolarization current J and high-frequency capacitance Cs of the depletion layer in the semiconductor on gate potential Vg and the rate of potential change βv = dVg/dt = const. In the general case, even for a single type of mobile ions in the insulator, the dynamic current–voltage characteristics (CVCs) may exhibit three current peaks. The transfer of some nonlocalized (free) ions at the interface through the insulator, depletion of ion traps, and decomposition of neutral ion–electron associates are responsible for the peaks. The sequence and number (down to one) of the peaks depend on the activation energies of the associated processes, value of βv, and energy of activation of minority carrier generation. Depending on these parameters, the peaks may appear, disappear, or merge into a broad peak, which may erroneously be identified as a result of the depletion of ion traps that have an energy spectrum. In other words, the CVC with a single peak does not necessarily mean that there exist several types of mobile ions. From the J, Cs = f(T, Vg, n0, βv) families, one can discriminate between purely ionic and electronic phenomena and identify free, neutralized, and/or trapped ions present at the interface (here, T is the temperature and n0 is the initial total surface concentration of particles (ions) and neutral associates at the interface).