ANOMALOUS HALL EFFECT AND OTHER RELATED NONLINEAR BULK EFFECTS.

Abstract : Incoherent Gunn domains generated by brief current pulses through fairly heavily doped n-GaAs contain high electric fields and produce a strong bulk ionization. Changes in conductivity, and the recombination radiation, resulting from this pulse-ionization have been studied. The decay times of conductivity and of light output are both of the order of 10 to the -8th power sec, but differ; measurement of their magnitudes in conjunction with the output power in GaAs with n approx. 10 to the 17th power/cc allows the radiative recombination cross section to be deduced. At room temperature, it is 5 x 10 to the -18th power square cm, in reasonable agreement with the van Roosbroeck-Shockley theory. The light output (bulk electroluminescence) originates in band-to-band recombination. At 83 K, stimulated emission has been obtained in material with n = 4 x 10 to the 17th power/cc. The bandwidth narrows to 40 A, and the power output increases to 20,000 W/sq cm (5 W for the samples measured) in pulses of the order of 2 x 10 to the -9th power-sec duration. Studies of the spectral distribution of spontaneous photoluminescence and of bulk electroluminescence have shown the transition from band-to-acceptor to band-to-band recombination, and also suggest, in the light of detailed balance considerations, that excitons play little part in the recombination process. Theoretical studies of the propagation of a light wave through transversely drifting change carriers have been made, on a classical basis. The interaction via the Lorentz field changes the propagation constant of the wave. Computer results are given which show that when the drift velocity is very high, a growing wave can exist.