Silicon-germanium base heterojunction bipolar transistors by molecular beam epitaxy

Iyer, Subramanian S.; Patton, G.L.; Delage, S.S.; Tiwari, Sandip; Stork, J.M.C.

doi:10.1109/iedm.1987.191578

Cited by 54 publications

(16 citation statements)

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“…Device engineers came up with concepts like graded dopant profiles, SiGe [1] and SiGe:C [2] base layers, elevated base structures [3], etc. Regarding the collector, selectively implanted collectors (SIC) were introduced to increase both the cutoff frequency f t and the maximum frequency of oscillation f max .…”

mentioning

confidence: 99%

The influence of collector dopant profile on breakdown voltage and cutoff frequency of Si‐based RF bipolar transistors

Schippel

Schwierz

2006

Phys. Status Solidi (c)

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The cutoff frequency ft and the collector-emitter breakdown voltage BVCEO are computed for various types of Si-based bipolar junction transistors with different doping profiles of the selectively implanted collectors (SIC). In particular the influence of the SIC profiles on the f t vs. BVCEO characteristics is investigated. It is shown that for slow BJTs the effects of collector profile variations are negligible. For fast HBTs, however, the actual SIC profile has a significant influence on the f t vs. BVCEO characteristics. Graded and steplike SIC profiles show an improvement compared to constant SIC doping, while retrograde profile deteriorate device performance.Motivation and introduction During the evolution of RF bipolar transistors, much efforts were spent to optimize the base design. Device engineers came up with concepts like graded dopant profiles, SiGe [1] and SiGe:C [2] base layers, elevated base structures [3], etc. Regarding the collector, selectively implanted collectors (SIC) were introduced to increase both the cutoff frequency f t and the maximum frequency of oscillation f max . In this work we focus on the collector-emitter breakdown voltage BV CEO and its relation to the cutoff frequency f t for differently designed SICs of Si-based RF bipolar transistors. This is done by two-dimensional numerial device simulation. To get a general picture, several distinctly different types of bipolar junction transistors were investigated: A SiGe HBT with a graded Ge profile in the base ("triangular" design) and a second SiGe HBT having a much higher Ge content in the entire base, thus allowing higher dopant concentration in the base than in the emitter ("true" HBT or rectangular design). Additionally two conventional NPN BJTs with diffusion respectively drift as the dominant mechanism for the electron transport through the base were simulated.

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confidence: 99%

The influence of collector dopant profile on breakdown voltage and cutoff frequency of Si‐based RF bipolar transistors

Schippel

Schwierz

2006

Phys. Status Solidi (c)

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“…The angles related to the "1" in the normalized curves are critical angles. The porosity of SiGe layer is defined by the following equation (2): ρ = 1 -(θ PC ) 2 /(θ C ) 2 [1] where θ PC is porous SiGe layer's critical angle and θ C is Strained SiGe epilayer's critical angle. Table 1 Hence, it explains that Si-Ge peak is vanished and Ge-Ge peak is raised in Raman spectra.…”

Section: Resultsmentioning

confidence: 99%

“…Strained p-SiGe base greatly improved performance of npn Si BJT with the SiGe layer thickness of several tens of nanometer (1). Due to differences of oxide properties between Si and Ge (2), wet process may make some changes on strained SiGe layers, especially on the layers with higher Ge fraction and without Si-cap layer passivated on the top.…”

Section: Introductionmentioning

confidence: 99%

X-ray and Raman Characterization of Strained SiGe Layers Treated by Stain Etching

2013

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The characterization of porous SiGe layers by means of X-ray and Raman spectroscopy is reported. The strained p-SiGe layers are stain etched to form porous SiGe layers which are studied by HRXRD and compared to the control sample. The rocking curves show that Si-Ge peak is no significant change at the beginning of stain etching and collapses for 30 seconds treatment. However, Raman spectroscopy shows Si-Ge peak in the SiGe epilayer almost vanished at the beginning of etching and meanwhile, Ge-Ge peak raised. XRR shows small changes in the thickness of SiGe layers for short time stain etching but critical angels change significantly. It appears that Si and Ge in the SiGe layer have different behaviors during the stain etching.

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“…This has been an essential step to reduce the lattice mismatch. The first realized SiGe HBT has been reported in 1987 by IBM researchers [17].…”

Section: Historymentioning

confidence: 99%

High speeds in a single chip

et al. 2009

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Silicon-germanium base heterojunction bipolar transistors by molecular beam epitaxy

Cited by 54 publications

References 0 publications

The influence of collector dopant profile on breakdown voltage and cutoff frequency of Si‐based RF bipolar transistors

The influence of collector dopant profile on breakdown voltage and cutoff frequency of Si‐based RF bipolar transistors

X-ray and Raman Characterization of Strained SiGe Layers Treated by Stain Etching

High speeds in a single chip

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