Germanium content and base doping level influence on extrinsic base resistance and dynamic performances of SiGe:C heterojunction bipolar transistors

Abstract

We describe a reliable technique to separate the different contributions to the apparent base resistance (R B = R Bx + X R Bi ) of silicon germanium carbon (SiGe:C) heterojunction bipolar transistors (HBTs). The extrinsic base resistance (R Bx ) is quantified using small-signal measurements. The base-collector junction distribution factor (X) and the intrinsic base resistance (R Bi ) are extracted from high frequency noise (MWN) measurements. This method is applied to five different SiGe:C HBTs varying in base doping level and germanium content. The results show that high doping levels improve high frequency noise performances while germanium gradient helps to maintain outstanding dynamic performances. This method could be used to elucidate the base technological configuration that ensures low noise together with remarkable dynamic performances in state-of-the-art SiGe:C HBTs.

Influence of temperature on transit times and microwave noise performances of SiGe HBT

“…From this last formula, we see that the square of f MAX is directly proportional to f T and inversely proportional to the product R B C BC , and as stated in [19] and references therein, for the modern HBTs the product R Bx C BC is greater than R Bi XC BC . Hence, f MAX,T2 is higher than f MAX,T1 because f T,T2 is greater than f T,T1 , and because R Bx,T2 lower than R Bx,T1 (see table 3).…”

“…The contributions to R B are [20]: R B ≈R Bx +X R Bi where X is the BC distribution factor, R Bx and R Bi are the extrinsic and intrinsic base resistances, respectively. The separation of each term of the triplet {R Bx , X, R Bi } uses the method described in [19,21] and is based on both the S-parameters and the noise measurement at 300 K. At 40 K we used the same value for X as that obtained at 300 K. Figure 1(b) shows a satisfactory agreement between the simulated (continuous black lines) and measured (circles) S-parameters of T2 at the two temperatures. For the three devices, the agreement is similar at all bias levels.…”

“…We used an analytical-based method to extract some of the small-signal parameters at 300 K and at 40 K. The extraction of the emitter resistance (R E ), the apparent base resistance (R B ), the BC capacitance (C BC ), the BE dynamic resistance (R Π ), the BE capacitance (C Π ), the transconductance (g m ), and its high-frequency excess delay time (τ Π ) were determined using the strategy described in [19]. The contributions to R B are [20]: R B ≈R Bx +X R Bi where X is the BC distribution factor, R Bx and R Bi are the extrinsic and intrinsic base resistances, respectively.…”

Novel Frequency Dependent OFET Attenuator Using ClInPc with Al2O3 Embedded Nanoparticles in Nylon 11 for Flexible Electronics

“…For biosensing and radiofrequency applications the time response and gain are important to perform with high speed, high sensitivity, and great accuracy (Li et al,2014;Sarangadharan et al, 2019). The device gain is voltage-frequency dependent and can be altered by the apparent gate resistance of the semiconductor in use, as well as the device architecture (Nakamura et al, 1992;Ramirez-Garcia et al, 2014). Although in the design and manufacture of an OFET, factors such as the device architecture, substrate, and terminals type are considered.…”

“…There are various ways to analyze and model transistors, which do not present a defined configuration, such as S-parameters and π parameters. The importance of these methodologies is that the application of the device may include small-signal and high frequency noise device modelling (Ramirez-Garcia et al, 2014). When applying higher frequencies to an OFET device, there is a determined stage delay, usually in µs, which is defined as the charging time.…”