Frequency Performance Of Transistors Research Articles

Novel fluctuation-based approach to optimization of frequency performance and degradation of nitride heterostructure field effect transistors

The fluctuation-based technique has been used to shed light onto the physical processes responsible for the performance of nitride heterostructure field effect transistors. A non-monotonic dependence of hot-phonon lifetime on the density of two-dimensional electron gas (2DEG) is found and interpreted in terms of plasmon-longitudinal-optical-phonon resonance. Experimental data show that the hot-phonon lifetime acquires the shortest value in the vicinity of the resonance. At a fixed 2DEG density of the 2DEG, the resonance can be tuned in with supplied electric power. The signatures of the resonance have also been resolved in frequency performance of the transistors and their degradation. In particular, the transistor operation is the fastest and the reliability is the highest when the hot-phonon lifetime is the shortest. (online colour at: www.pss-a.com) Drain current degradation (stars [8]) correlates with hot-phonon lifetime (curve).

Effects of transverse diffusion and transverse stored charge in alloy transistor base†

Transverse diffusion of minority carriers under the action of a transverse concentration gradient in the base, which will exist even in the absence of surface recombination, is shown to make an appreciable contribution to the base current and is to be taken into account in considering transistor action. The dependence of transistor current gain on base geometry is traced to this factor. The role hitherto assigned exclusively to surface recombination in this regard and in several areas of disagreement between the predictions of the one-dimensional theory and experimental observations now appears to be largely assignable to transverse diffusion. Transverse diffusion processes in alloy junction type and grown junction type base geometries are contrasted. The adverse effect of transverse stored charge on the high frequency performance of transistors is analysed and their effect on increasing the ‘ effective base transit time ’ discussed. The possibility of localized reduction of volume lifetime in the base in...