| Photo (h(nu) > E(,g)) and dark-capacitance transients are measured between 87K and 300K in Cr-SiO(,2)-n Si MIS capacitors with 20 to 176 (ANGSTROM) thick oxides. A 10 MHz fast capacitance bridge and an auto- mated data acquisition and evaluation system are built to measure transients from 10('-6) sec to 10('5) sec. From these measurements detailed information on the relaxation of inversion charge and tunneling parameters of interface traps has been obtained.; The observed fluence tF of the charge in interface and inversion layer exhibits as function of time three distinct maxima. A theoretical study of the two governing nonlinear differential equations--Shockley-Read-Hall recombination in interface traps, and continuity equation for holes in the valence band--shows that the first peak is caused by recombination in silicon bulk traps while the second and third peaks are generated by tunneling recombination in interface traps. These equations are solved for the time dependent occupancy f(t), the hole capture rate p(t), and the fluence components tH(,p) and tH(,m) due to hole emission into the valence band of the semiconductor and the conduction band of the metal. Theory and experiment agree.; The following interface trap and tunneling parameters are extracted from measurements. The geometric mean of thermal capture cross sections SQRT.((sigma)(,n)(sigma)(,p)), the interface trap density D(,it) and the distribution D(,(nu))(ln(nu)(,m)) of the logarithmic tunneling rate, ln(nu)(,m), of traps near midgap, are obtained from measurements of photo-capacitance transients. The trap density, D(,it) (E), and the centerline, ln(nu)(,m)(E) = ln(nu)(,m)(E), of the distribution D(nu)(ln(nu)(,m),E), as function of trap energy E above midgap, are obtained from dark-capacitance transients.; These data are analyzed to obtain the energy dependent tunneling attempt-to-escape frequency (nu)(,mo) decreasing from 10('15.4(+OR-)0.6) Hz at midgap to about 10('10) Hz at the silicon conduction band edge, nearly energy independent tunneling attenuation coefficient, (alpha) = 1.05 (ANGSTROM)('-1), and standard deviations, (sigma)(,(nu)) = 2.5 (+OR-) 0.2, of the distributions of the tunneling rate ln(nu)(,m), and (sigma)(,d) = 2.4 (+OR-) 0.3 (ANGSTROM) of the tunneling distance d of the traps from the metal.; The measured value (nu)(,mo) = 10('15.4) Hz of the tunneling attempt-to-escape frequency at midgap is predicted by Lundstrom's (delta)-function model; however, its energy dependence remains unexplained and may be related to an observed energy dependence of the thermal cross section. The measured attenuation coefficient (alpha) = 1.05 (ANGSTROM)('-1) is consistent with a Franz two band dispersion relation in SiO(,2) with effective mass 0.49. Finally the measured standard deviation (sigma)(,d) of the tunneling distance distribution is compatible with the existence of a monoatomic transition region between silicon and silicon dioxide. |
