Optimizing N-p-n and P-n-p heterojunction bipolar transistors for speed

A thermionic-emission-diffusion model for graded base Pnp heterojunction bipolar transistors

“…Subsequently, the drift-diffusion model is employed to a͒ Electronic mail: kroenker@ece.uc.edu describe hole transport across the quasi-neutral base where the effects of compositional grading have been included. This article extends the work of Hutchby, 21 Sunderland and Dapkus, 22 and Yuan 23 by including: ͑1͒ the physics of hole thermionic-emission-diffusion injection at the emitter-base heterojunction, ͑2͒ the effects of linear compositional grading in the base, and ͑3͒ the calculation of the recombination currents in the base current including the effects of compositional grading. In addition, it incorporates a more realistic boundary condition for the hole concentration at the collector end of the quasi-neutral base, i.e., a finite concentration sufficient to carry the hole collector current.…”

“…6,7,[21][22][23] In particular, this approach follows that of Grinberg et al 16,17 where the electron thermionic-field-emission current across the heterojunction spike at the emitter-base heterojunction is matched with the diffusion current in the base to derive the excess carrier concentration at the emitter end of the quasi-neutral base. In this article an analogous approach is followed for the holes based on a more general description of carrier injection across the heterojunction following Stettler and Lundstrom.…”

Symmetric P-n-P InAlAs/InGaAs double-heterojunction bipolar transistors fabricated with Si-ion implantation

“…[2] not only has obvious advantages for integrated injection logic (I L) and emitter-coupled logic (ECL) circuits, but it may also improve its high-speed performance in the emitter-down configuration due to a reduction of the collector capacitance [ 11. Recent analysis suggests P-n-p HBT's have the potential for performance approaching that of N-p-n HBT's [3]. We expect the InGaAs/InAlAs system, lattice-matched to InP, to be very promising for the symmetric P-n-P DHBT because 1) the large conduction-band offset, approximately 0.5 eV, improves the blocking of hole injection from the external portion of the emitter in the emitter-down configuration, 2) the turn-on voltage is expected to be smaller than that of the N-p-n GaAs/AlGaAs HBT, which can make the power dissipation very low, and 3) the large electron mobility in n-InGaAs can make the base resistance very low.…”

Hole transport and quasi-Fermi level splitting at the emitter-base junction in Pnp heterojunction bipolar transistors

“…[4][5][6][7][8] However, there have been few theoretical studies of Pnp HBTs. [9][10][11][12][13][14][15][16][17] In particular, the role of hole thermionic emission, tunneling and space charge region drift diffusion at the emitter-base heterojunction have not been fully investigated. Due to the hole's larger effective mass and lower mobility, differences from the electron case are possible.…”

“…The result is compared with the current expected when limited by hole diffusion in the quasineutral base, which has been assumed in the previous analysis of PnP HBTs. 10 Finally, the quasi-Fermi level variation across the emitter space charge region, the heterojunction interface, and quasineutral base are determined and compared with results obtained from a commercial numerical simulator. In Sec.…”