Reliability characteristics of mesa-etched isolated emitter structure AlGaAs/GaAs HBTs with Be-doped base

Nozu, T.; Tsuda, Koji; Asaka, M.; Obara, M.

doi:10.1109/gaas.1992.247201

Cited by 6 publications

(4 citation statements)

References 8 publications

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“…Thermal and recombination-aided diffusion of crystalline defects from the bulk semiconductor to the heterointerface in abrupt junction HBTs has been suggested to account for increases in base current during burn-in of AlGaAs/GaAs HBTs. Additional evidence of the role of the emitter-base heterojunction was obtained in a study that found that implant-isolated HBTs degrade more than mesa-isolated HBTs [3]. The degradation consisted of a shift in V be and a decrease in h FE , apparently resulting from the contact of the emitter-base junction edge to the defect-laden implant region.…”

Section: Reliabilitymentioning

confidence: 96%

“…For Al. 3 Ga. 7 As/GaAs HBTs, ∆E g ≈14.6 kT and exp (∆E g /kT) ≈ 2 × 10 6 .Thus, the ∆E g difference provides a significant improvement in I n /I p over the bipolar transistors case (∆E g = 0). This property of HBT devices allows the fabrication of a heavily doped base and a lightly doped emitter without affecting current gain too much.…”

Section: B Operating Principlesmentioning

confidence: 96%

“…The parameters in Equations (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19) and (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) are q, the electronic charge; k, Boltzmann constant; T, temperature; A, the emitter-base junction area; D n , the electron diffusivity in the base; W, the base width; N E , the emitter doping concentration; D p , the hole diffusivity in the emitter; and L p , the hole diffusion length in the emitter. Obviously,…”

Section: B Operating Principlesmentioning

confidence: 99%

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Heterojunction bipolar transistors

Baca¹,

Ashby²

2005

Fabrication of GaAs Devices

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AlGaAs/GaAs heterojunction bipolar transistors (HBTs) are used for digital and analog microwave applications with frequencies as high as Ku band. HBTs can provide faster switching speeds than silicon bipolar transistors mainly because of reduced base resistance and collector-to-substrate capacitance. HBT processing requires less demanding lithography than GaAs FETs, therefore, HBTs can cost less to fabricate and can provide improved lithographic yield. This technology can also provide higher breakdown voltages and easier broad-band impedance matching than GaAs FETs.In comparison with Si bipolar junction transistors (BJTs), HBTs show better performance in terms of emitter injection efficiency, base resistance, base-emitter capacitance, and cutoff frequency. They also offer good linearity, low phase noise and high power-added efficiency. Table 3-3 shows a comparison of typical device characteristics between AlGaAs/GaAs HBTs and Si BJTs. HBTs are used in both commercial and high-reliability applications, such as power amplifiers in mobile telephones and laser drivers. Table 3-3. Comparison of AlGaAs/GaAs HBT and Si bipolar transistors. Parameter AlGaAs/GaAs HBT Si BJT Forward transit time, τ F 4 ps 12 ps Early voltage, V a 800 V 25 V Collector-substrate capacitance, C cs~0~1 5 fF Base resistance, R b 70 W 200 WFor NPN BJTs, a useful figure of merit that is important in determining the current gain is the ratio, electron current injected from the emitter into the base hole current injected from the base into the emitterThis ratio is called the injection efficiency, and it is usually optimized in BJTs by highly doping the emitter and lightly doping the base. High injection efficiency is obtained in an HBT by using a material with a larger energy band gap for the emitter than that used for the base material. The large energy band-gap emitter blocks injection of holes from the base. Therefore, the doping concentration in the base and emitter can be adjusted over a wide range with little effect on injection efficiency. In the normal operation of a bipolar transistor, the collector-base junction is reverse biased or at least not forward biased enough to cause appreciable injection current. The collector and base material are the same in most HBTs, although some use wide band-gap collector materials to improve the collector base breakdown voltage.It follows that AlGaAs/GaAs HBTs benefit from the following advantages:(1) Lower forward transit time along with a much lower base resistance (due to the much higher base doping concentration), giving increased cutoff frequency f t .

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Section: Reliabilitymentioning

confidence: 96%

Section: B Operating Principlesmentioning

confidence: 96%

Section: B Operating Principlesmentioning

confidence: 99%

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Heterojunction bipolar transistors

Baca¹,

Ashby²

2005

Fabrication of GaAs Devices

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“…It was particularly important to limit Be doping to modest levels (~1x10 19 /cm 3 ) to avoid performance drift caused by diffusion of Be. It was also necessary to use modest Je [5], which limits performance.…”

Section: B Evolution Of Wearout Reliability In Gaas Hbtsmentioning

confidence: 99%

GaAs HBT Reliability

Yeats

Low

Alt

et al. 2008

2008 IEEE Compound Semiconductor Integrated Circuits Symposium

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We discuss the many factors affecting the reliability of GaAs HBTs that we have encountered starting from the early days of AlGaAs-emitter HBTs through the present day use of InGaP-emitter HBTs. We discuss both wearout and infancy failure modes and try to distinguish fundamental (i.e., unavoidable) from nonfundamental failure modes. We have found that infant failures are dominated by substrate dislocation density, which can limit long-term-reliable circuit sizes to under ~1000 transistors.

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