The inhibition of negative resistance dipole waves and domains in n-GaAs

Expressions describing the growth and propagation of infinitesimal space-charge waves in the presence of a differential negative resistance are derived, and conditions for the inhibition of dipole waves and domains inn-GaAs of resistivity greater than 10Ω-cm at 300°K are obtained. Thermoelectric effects are estimated and found to be small for carrier densities much less than 1015cm-3. Taking the negative differential resistivity to be larger than the ohmic resistivity by a factor of 102leads to 1) condition for inhibition of dipole waves:nl² 10⁹cm-12) condition for inhibition of stable domains:nl 10¹²cm-2whenn= electron density andl= specimen length. The relevance of these results to explaining the phenomena observed in amplifying crystals is pointed out. It is suggested that the condition for amplification is({10⁹}{n})1/2 l {10¹²}{n}.