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Theoretical study of tunnelling current in the access region of various heterojunction field-effect transistor structures

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  • Physics


Theoretical study of tunneling current in the access region of various hnulleterojunction field-effect transistor structures Theoretical study of tunneling current in the access region of various reduction.3,4 optimized toward highest electron density and so to lowest The reduction of source-gate spacing is considered to be the most difficult and least reproducible step for high-yield device processing. The conditions for source-gate spacing reduction can however be relaxed by reducing the resistance of the access region. In this article a new structure is pro- posed which leads to a reduction of the access resistance due to enhanced tunneling and increased current density in vari- ous parts of the heterostructure. A quantum-mechanical modeling program5,6 has been used to compare the resistance value and linearity of the current–voltage characteristics with those of several other heterostructures achieving access resistance reduction. To obtain a quantitative description of the contribution of the tunneling current on one side and the thermionic/diffusion current on the other side, the current transport is analyzed as a function of temperature. Moreover, conclusions are drawn resistance. Although when the resistance across the vertical heterojunction diode is negligible, the total resistance can be reduced by reducing the top-layer resistance. Reduction of the top-layer resistance by replacing GaAs by InyGa12yAs has been described by Kuroda et al.,7 and by inserting an InyGa12yAs quantum well between the electron supply layer and the top layer it has been described in former work.2 These two techniques, however, do not take into account the increase in barrier height of the electron supply layer at the interface with the top layer, due to the larger heterojunction dipole which is created. As the vertical heterojunction diode resistance then becomes significant, the improvement ob- tained by these two techniques remains marginal. Reduction of the vertical resistance has been obt

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