CHAOTIC CONDUCTIVITY OSCILLATION IN N-TYPE AND P-TYPE SI

Chaotic conductivity oscillations in n-Si and p-Si have been investigated in the freeze-out temperature range between 15 and 37 K. The oscillations were found in zero magnetic field for n-Si<110>, n-Si<111> and p-Si<111>. For n-Si<100>, on the contrary, chaotic behaviours were found only in the presence of a magnetic field B of about 18 T. The fundamental oscillation frequency f and the attractor dimension D for n-type Si were obtained as f = 5.3 kHz and D = 1.1-1.54 for <111>, f = 870 Hz and D = 1.1-2.0 for <110>, and f = 12 kHz and D = 1.1-4.2 for <100>, respectively. For p-Si<111>, f = 1.25 kHz and D = 1.6-2.6 were obtained in zero magnetic field. The fractal structure was directly shown by the number density of the current trajectory crossing a special phase in the phase space for n-Si<110> sample. The chaotic oscillation was observed for the doped n-Si<111> with N(D) = 6 x 10(16) cm-3 at T = 15 K, whilst only harmonic oscillation was observed for a higher purity sample of N(D) = 10(14) cm-3. The fundamental oscillation frequency for n-Si<100> decreased by 20% with increasing magnetic field up to 16 T in an electric field E = 100 V cm-1.