The system of nonlinear equations describing the stationary st,ate of a semiconductor with negative bulk differential conductivity is analpsed in t.he "phase plane". The negative differential conductivity is considered to arise from either the field dependencc of the electron concentration (due to t.he recombination process) or the field dependence of the mobility. Possible spatial variations of the field along the sample have a step-like form and correspond to two different values of the saturation current. The current-voltage characteristics and the field distributions are studied experimcntdly in n-type germanium samples containing p a r~l y compensatd copper. It is found that the saturation current corresponds to the peak of the cii rrent-field curve of D spatially homogeneous sample. The electric field in the low and high field regions, as well as the location of these regions in the sample, are found to be in satisfactory agreement with thcory.
Steady state and transient current-voltage characteristics are studied for Cu-doped n-type Ge samples with the upper Cu level ( E , -0.26) eV partly compensated. The field strength is varied from -1 V/cm to lo4 V/cm. The I -U curves obtained are sublinear a t field strengths above -100 V/cm. A study is made of the effect of temperature and of the spectrum of the incident light upon both the steady state and the kinetics of the photocurrent. Negative differential conductivity and coherent low frequency oscillations are observed a t nitrogen temperatures with high illumination. The nonlinear effects are shown to be due mainly to the reduction of electron concentration in the conduction band. This could be ascribed to the field dependence of a; the probability of electron capture by the doubly charged Cu ions. In the strong electric fields the crystals are becoming inhomogeneous due to the formation of strong-and weak-field regions. The possible influence of these inhomogenities on the nonlinear effects is discussed and the change of a; in the strong field is estimated.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.