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

Abstract

Analysis of collector-emitter offset voltage of InGaP/GaAs composite collector double heterojunction bipolar transistorAn analytical model which matches thermionic-emission-diffusion of holes across the emitter-base heterojunction with drift-diffusion transport across a graded base has been developed and used to examine the performance capabilities of InP-based Pnp heterojunction bipolar transistors ͑HBTs͒. Hole drift-diffusion across the emitter-base space charge region is shown to be of comparable importance to thermionic emission in controlling hole injection into the base. The effects of compositional base grading on the recombination currents is also taken into account. Compositional grading of the base is shown to enhance the device's current gain by as much as a factor of 10 by reducing recombination in the quasi-neutral base. More importantly, compositional base grading significantly reduces the base transit time which improves the device's peak cutoff frequency by as much as a factor of 1.5. A cutoff frequency as high as 35 GHz is found to be possible. The analysis indicates that composition grading of the base can be useful in developing high performance Pnp InP-based HBTs.

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

“…͑14͒ and ͑15͒, has been employed in the development of a complete analytical model for the Pnp HBT as described elsewhere. 17 The pur-pose of this article is to examine the implications of the result on hole injection and transport and to test its accuracy. In Sec.…”

“…[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.…”

Performance optimization of Pnp InGaAs/InP heterojunction phototransistors

“…The HPTs made of III-V compound semiconductors have been studied for two decades for its potentials as highperformance photodetectors [9,10], such as AlGaAs/GaAs and InGaAs/InP material systems. However, the HPTs also have some drawbacks that limit their applications in optoelectronic systems.…”