Double-layer collector for heterojunction bipolar transistors (original) (raw)
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We have demonstrated a heterojunction bipolar transistor using a novel compound collector (CCHBT) design that allows a low-knee voltage and high-breakdown voltage to be obtained simultaneously. The novel aspect of this design is to use a short wide band-gap collector only over a narrow portion of the collector, where the field is highest. This allows support of high fields while maintaining a low overall collector resistance due to the higher mobility of the narrow band-gap material. We demonstrate an offset voltage reduction of about 35% and a knee-voltage reduction of 30%, while increasing both BVCEO and BVCBO by 20 and 27%, respectively, compared to a single heterojunction device of the same collector length.
Heterojunction bipolar transistor design for power applications
IEEE Transactions on Electron Devices, 1992
Design rules of AIGaAsIGaAs heterojunction bipolar transistors for power applications are presented and compared to those for Si microwave power transistors. Concepts discussed include the tradeoff between power gain, output power, power-added efficiency in the layout design, layer structure selection, and thermal design.
Design study of AlGaAs/GaAs HBTs
IEEE Transactions on Electron Devices, 1990
The frequency performance of AlGaAs/GaAs heterojunction bipolar transistors (HBTs) having different layouts, doping profiles, and layer thicknesses was assessed using the BIPOLE computer program. The optimized design of HBTs was studied, and the high current performances of HBTs and polysilicon emitter transistors were compared. It is shown that no current crowding effect occurs at current densities less than 1×105 A/cm2 for the HBT with emitter stripe width SE<3 μm, and the HBT current-handling capability determined by the peak current-gain cutoff frequency is more than twice as large as that of the polysilicon emitter transistor. An optimized maximum oscillation frequency formula has been obtained for a typical process n-p-n AlGaAs/GaAs HBT having base doping of 1×10 19 cm-3
Thermal design studies of high-power heterojunction bipolar transistors
IEEE Transactions on Electron Devices, 1989
Abstruct-A theoretical thermoelectro-feedback model has been developed for thermal design considerations of high-power GaAlAs/ GaAs heterojunction bipolar transistors (HBT's). The power-handling capability, thermal instability, junction temperature, and current distributions of HBT's with multiple emitter fingers have been numerically studied. The calculated results indicate that power HBT's on Si substrates (or Si as the collector) have excellent potential power performance and reliability. The power-handling capability on Si is 3.5 and 2.7 times as large as that on GaAs and InP substrates, respectively.
GaAs Heterojunction Bipolar Transistor Emitter Design
We demonstrate that GaAs-based HBTs with very low base currents at both low and high injection levels can be achieved using either Al 0.35 Ga 0.65 As or InGaP in the emitter with the proper optimization of structure and growth. We observe an order of magnitude reduction in space charge recombination current as the Al composition, and hence the energy-gap, of the emitter increases from 25% (1.77 eV) to 35% (1.89 eV). AlGaAs/GaAs HBTs with approximately 35% Al have the same energy-gap as InGaP and exhibit comparable space charge recombination in large area devices (L = 75 x 75 µm 2 ). Moreover, this reduction in the space charge recombination in Al 0.35 Ga 0.65 As/GaAs HBTs can be achieved while maintaining a low turn-on voltage and high DC current gain over a wide range of current densities. Small area devices (L = 1.4 x 3 µm 2 ) fabricated with an Al 0.35 Ga 0.65 As emitter and a base sheet resistance of 330 Ω/V exhibit very high DC current gain at all bias levels, with a DC current gain exceeding 140 @ 25 A/cm 2 and a peak DC current gain of 210 @ 26 kA/cm 2 . The temperature dependence of the peak DC current gain is significantly improved over a similar structure with a 25% AlGaAs emitter. The RF performance of the 35% AlGaAs structure is also comparable to the 25% structure, with an f t of 34 GHz and an f max of 55 GHz.
Material-based comparison for power heterojunction bipolar transistors
IEEE Transactions on Electron Devices, 1991
A figure of merit based on material parameters has been used for a comparison of various Heterojunction Power Bipolar Transistors (HBT's). The general tendency is for use of narrow-bandgap materials such as Ge or InGaAs as the base and wide-bandgap materials such as AIGaAs, InP, Sic, or GaN as the collector, technology permitting.
The Safe Operating Area of GaAs-Based Heterojunction Bipolar Transistors
IEEE Transactions on Electron Devices, 2000
The safe operating area (SOA) of GaAs-based heterojunction bipolar transistors has been studied considering both the self-heating effect and the breakdown effect. The Kirk effect induced breakdown (KIB) was considered to account for the decrease of the breakdown voltage at high currents. With reasonable emitter ballastors, the KIB effect was shown to be the major cause for device failure at high currents, while the thermal effect controls the low current failure. The effect of emitter resistance and base resistance on device stability was also studied. While the emitter resistance always improves the device stability by expanding the SOAs, the base resistance degrades SOAs when the KIB dominates the failure mechanism. The effect of the base resistance on SOAs was explained by its control on the flow of the avalanche current. Since the KIB effect depends on the collector structure, it was shown that a nonuniformly doped collector can effectively improve the SOAs.
Power performance of InP-based single and double heterojunction bipolar transistors
IEEE Transactions on Microwave Theory and Techniques, 1999
The microwave and power performance of fabricated InP-based single and double heterojunction bipolar transistors (HBT's) is presented. The single heterojunction bipolar transistors (SHBT's), which had a 5000-Å InGaAs collector, had BV CE0 of 7.2 V and J C max of 2 2 10 5 A/cm 2. The resulting HBT's with 2 2 10 m 2 emitters produced up to 1.1 mW/m 2 at 8 GHz with efficiencies over 30%. Double heterojunction bipolar transistors (DHBT's) with a 3000-Å InP collector had a BV CE0 of 9 V and J C max of 1.1 2 10 5 A/cm 2 , resulting in power densities up to 1.9 mW/m 2 at 8 GHz and a peak efficiency of 46%. Similar DHBT's with a 6000-Å InP collector had a higher BV CE0 of 18 V, but the J C max decreased to 0.4 2 10 5 A/cm 2 due to current blocking at the base-collector junction. Although the 6000-Å InP collector provided higher f max and gain than the 3000-Å collector, the lower J C max reduced its maximum power density below that of the SHBT wafer. The impact on power performance of various device characteristics, such as knee voltage, breakdown voltage, and maximum current density, are analyzed and discussed. I. INTRODUCTION P OWER amplifiers for wireless communication systems require high-frequency active devices that have acceptable gain, produce significant output power, and cause little signal distortion. In addition, hand-held units require power amplifiers with high power-added efficiency (PAE) in order to maximize battery lifetime. Due to their ability to handle high power densities at microwave frequencies, heterojunction bipolar transistors (HBT's) operating linearly under Classes A and AB are good candidates for such amplifiers. While their breakdown voltages are typically not as high as GaAs-based HBT's, the excellent high-frequency performance and lower turn-on voltage of InP-based HBT's make them of interest for wireless applications. The simplest InP-HBT designs use a single heterojunction between the emitter and base, with the base and collector both composed of InGaAs. However, the narrow-bandgap collectors Manuscript
IEEE Transactions on Electron Devices, 1996
Abstruct-We propose the use of base-ballasting resistance to guarantee absolute thermal stability in AlGaAdGaAs heterojunction bipolar transistors (HBT's). Base-ballasted HBT's are fabricated and the measured I-V, regression and S-factor characteristics are discussed. We present a numerical model which elucidates the reasons why the base-ballasting scheme is helpful to HBT's but is damaging to silicon bipolar transistors. We compare measured small-signal and large-signal performances of unballasted, emitter-ballasted, and base-ballasted HBT's.