Investigation of AlInAs/GaInAs heterostructure-emitter-confinement bipolar transistors

Abstract

In this paper, the performances of AlInAs/GaInAs heterostructure-emitter-confinement bipolar transistors including heterostructure-emitter bipolar transistors (HEBT) and superlattice-confinement bipolar transistors (SCBT) are demonstrated. Due to the elimination of the potential spike at the emitter-base junction, extremely low offset voltages of 40 and 80 mV are obtained for the studied HEBT and SCBT respectively. For the HEBT, due to the small hole diffusion length and the large neutral-emitter recombination current, a degraded current gain performance is observed. On the other hand, the SCBT exhibits a large differential current gain of 240 resulting from tunnelling injection which can reduce the spread of thermal distribution and the non-radiative recombination cross-section.

InGaP/GaAs superlattice-emitter bipolar transistor with InGaAs/GaAs superlattice-base structure

“…However, the conventional HBTs suffered from a large collector-emitter offset voltage ('V CE ) resulting from the difference between base-emitter (B-E) and basecollector turn-on voltages, which severely limits the minimum operated voltage and causes the high power consumption in circuit applications [1]. It is well known that two usual approaches, i.e., the reduction of potential spike at B-E junction [2][3][4] and the employment of a small energy-gap layer as base material [5][6][7], had been employed for the reduction of B-E turn-on voltage.…”

“…Over the past years, heterostructure-emitter bipolar transistor (HEBTs) with B-E homojunction [2][3][4], have been demonstrated to reduce the potential spike at B-E junction. Nevertheless, the thickness of the small energy-gap emitter layer is critical to determine the device performance.…”

“…Nevertheless, the thickness of the small energy-gap emitter layer is critical to determine the device performance. The transistor will act with inferior confinement effect for holes and cause the large charge storage in neutral-emitter region when the layer is too thick, while the undesirable offset voltage is still considerably large when the layer is too thin [3]. The second approach to improve the turn-on voltage is to adopt small energy-gap InGaAs ternary alloys as base layer for the GaAs-based HBTs.…”

The influence of a -doped sheet on DC performances of InP/InGaAs heterojunction bipolar transistors

“…However, unlike the case for the lattice-matched Al x Ga 1−x As/GaAs material systems, the thickness of the In x Ga 1−x As strained layer is severely limited and it must be accurately controlled although both linear and parabolic grading compositions are applicable for InP/InGaAs HBT's. Over the past few years, heterostructure-emitter bipolar transistors have been proposed and fabricated to achieve low offset voltage [7][8][9]. Moreover, a homojunction emitter will cause charge storage in the small-energy-gap emitter region and the transistor performs with an inferior confinement effect for holes.…”

“…Moreover, a homojunction emitter will cause charge storage in the small-energy-gap emitter region and the transistor performs with an inferior confinement effect for holes. So, the current gain might be degraded, particularly for an InGaAs-based HBT with small diffusion length under large forward B-E bias [8]. Recently, the In 0.53 Ga 0.25 Al 0.22 As/InP heterostructure with a nearly continuous conduction band has been proposed for improving the offset voltage.…”