Oscillatory instabilities (but not chaos) in the electrical properties of semiconductors due to nonlinear effects of an applied electric field have been known for a long time. The concept of chaos introduces a new means for analyzing and understanding these nonlinear semiconductor systems, and helps to establish the physical origin of the oscillations and non-linear behavior. A comprehensive investigation of oscillatory behavior, bifurcation and chaos in the electrical properties of narrow gap semiconductors (m- and p-InSb and Hg1-xCdxTe) that are controlled by impact ionization of shallow impurities will be carried out, with the goal of understanding the dynamics of deterministic nonlinear systems of narrow gap semiconductors, especially chaotic ones. Both experimental and mathematical modeling behavior will be investigated for period doubling tangent bifurcations, intermittency, quasiperiodicity, frequency locking, strange attractors, Lyapunov exponents, chaotic states, etc. Effects of various parameters--sample doping, lattice temperature, magnetic field, sample contacts, sample compensation, etc. on the chaotic behavior of both n- and p- type InSb will be studied. Models will be developed to better understand semiconductor dynamics and the relationship of the nonlinear oscillations/chaos to the role of the impurities. The PI will seek to discover how the nonlinear oscillations/chaos can be used to characterize the impurities in the samples. The results should have general applicability to other semiconductors which have similar properties. A major emphasis will be placed on studies at high magnetic fields (up to 120 kG).
