Selection and calculation of parameters of strip optical waveguides

Abstract

Experimental and theoretical work on hot electron emission is reviewed. The effects of impact ionization scattering and phonon scattering on the efficiency of a given material are examined. The impact ionization threshold is shown to depend only in a very broad manner on the energy gap of the material. For silicon carbide the threshold energy is larger than in silicon or germanium. However, there is little difference between the last two materials. No clear cut evidence exists regarding the relative importance of phonon and ionization scattering, but the relatively large emission currents observed from silicon carbide suggest that the latter is dominant. There appears to be no reason why germanium should be a less efficient material than silicon, despite the lower energy gap. In fact experimental evidence suggests that germanium is better. In silicon p-n junctions the emitted current originates at breakdown microplasmas, whereas in silicon carbide it appears to originate at other parts of the junction. This may be due to the pi-n nature of many silicon carbide junctions. It is suggested that experiments should be extended to other semiconductors with large band gaps.