Analysis and Numerical Simulation of the Dual-Gate Permeable Base Transistor

Abstract

Recent interest in novel transistor geometries to radically extending the high-frequency limit of three-terminal devices has stimulated the development of ,new technologies for fabricating submicrometer semiconductor structures. One such technology, the lateral growth of single-crystal semiconductor over metals and insulators, has been combined with submicrometer lithography in the fabrication of permeable base transistor (PBT) [1]- The distinguishing feature of PET is a thin tungsten grating which is embedded inside a single crystal semiconductor and is the gate (base) of the transistor. In this article the dud gate is used to reduce the idluence of drain voltage on the input current. Numerical solutions to the two-dimensional Poisson's equation and the continuity equation have been used to investigate the performance of the dual-gate PBT. The device geometry used in the numerical simulations is illustrated in Fig. 1. The constant potential contours of the initial device condition is shown in Fig. 2, in which the dotted he indicates the depletion edge of the Schottky contact. Fig. 3 shows the potential surface of the same device as Fig. 2 with V,=lV and Vg=0.3V. From Fig. 3, the barrier-limited mode of operation can be known. Fig. 4 shows the drain current density as a function of the gate bias. From Fig. 4(a) and Fig. 4@), the exponential transfer characteristic at the lower controfelectrode bias levels and a square-law transfer characteristic at higher bias levels as the conventional PBT [ 11 are observed, respectively. Fig. 5 shows the collector characteristics 5f the device with 0.16 pm tungsten grating stripes. According to Fig. 5, it reveals a transconductance (gd of 628 mS/mm, which is larger than the experimental results 12, 31 by one order. The results indicated that by proper choice of the carrier density and structure dimensions the dual gate PBT can operate in both depletion and enhancement mode, just the same as the conventional PBT [I, 4, 51. The results also indicated that the Early voltage is larger than that of the conventional PBT.