Interpretation of the common emitter offset voltage in heterojunction bipolar transistors

NRC publication: Ye

Influence of built-in drift fields on the performance of InP-based HBTs grown by solid-source MBE

The versatility of solid-source molecular beam epitaxy for the growth of InP/InGaAs heterojunction bipolar transistors (HBTs) is provided by its excellent control of doping and composition grading profiles in combination with its efficiency for carbon doping. Various designs using doping grading or composition grading in the base are investigated to provide a built-in quasi-electric field that enhances electron transport. All graded-base devices exhibit higher current gains (beta), as compared to uniform-base structures, but the beta improvements are found to be nonproportional to the generated built-in drift fields. The best performances are obtained with a 9% linear composition grading profile. As compared to conventionally grown uniform-base structures, the linearly graded-base HBTs show higher current gains (up to 42%), which is of particular importance particularly in analog and mixed-signal applications

High-speed selector-driver using abrupt delta-doped InP/InGaAs/InP DHBTs

This letter reports the potential of an InP-based double-heterojunction bipolar transistor (DHBT) using a thin highly doped n+-InP layer inserted at the base-collector junction. Molecular-beam-epitaxy-grown abrupt pulse-doped InP-InGaAs-InP DHBTs ensure very high current gains of »90, low saturation voltages of less than 1 V, and high cutoff frequencies of ~350 GHz. Using this technology, a compact high-speed high-voltage multiplexer-driver integrated circuit (IC) suitable for high-speed signal processing and communication systems has been designed and fabricated. The IC has successfully been measured at 112 Gb/s with very clear eye openings of up to 2 Vpp with a power consumption of 2W

High stability heterojunction bipolar transistors with carbon-doped base grown by atomic layer chemical beam epitaxy

We report the improved thermal stability of heavily C-doped GaAs layers using atomic layer chemical beam epitaxy (ALCBE). The use of ALCBE improves the crystal quality and reduces hydrogen incorporation in the epilayers by about a factor of 2, resulting in enhanced electrical dopant activity as compared to conventional growth techniques. This process has been successfully applied to the fabrication of InGaP/GaAs heterojunction bipolar transistors (HBTs) with a highly C-doped base grown by ALCBE and other layers grown by conventional CBE. Dc current gains up to 150, for a base doping layer of 3 \ufffd 1019 cm \ufffd 3, have been obtained. Moreover, the thermal stability of these devices is increased, as indicated by a post-growth annealing (650\ufffdC, 60 min) which induces only a slight current gain degradation of about 20% at high collector currents, to be compared to a degradation of 60% for HBTs conventionally grown by CBE.NRC publication: N

Crystallographic orientation effects on the performance of InP-based heterojunction bipolar transistors

We report the crystallographic orientation effects in InP-based heterojunction bipolar transistors (HBTs). The DC and RF characteristics of DHBTs fabricated on the same wafer were found to be dependent on the emitter orientation. Self-aligned InP/InGaAs DHBTs with [0 1 -1] emitter direction exhibit higher current gains, more stable and also better RF performance, while maintaining similar breakdown voltages, as compared to [0 1 1] oriented devices. Most of the differences are attributed to the resulting emitter-base sidewall profiles obtained after mesa etching. Without ruling out piezoelectric and stress effects, generally observed in III-V based HBTs, a contribution to the orientation effect, especially on the DC characteristics seem to be related to the more effective extrinsic base passivation for the [0 1 -1] orientation. For a given bias point, the maximum oscillation frequency (fmax) is also slightly higher in [0 1 -1] oriented devices, due to a smaller base resistance resulting from a smaller base-emitter spacing, while the cut-off frequency (fT) remains comparable in both orientations

Correlation between composition and stress for high density plasma CVD silicon nitride films

Intrinsic film stress is an important issue for the fabrication, performance, and application of a device. In the present study, a correlation between stress in high density plasma chemical vapor deposited silicon nitride films and their composition has been established. This has led to the low temperature deposition of low stressed films. The films exhibit a relatively negligible amount of chemically nonbonded hydrogen atoms. The density of the films calculated from the results of Rutherford backscattering spectroscopy and nuclear reaction analysis techniques is high, around 2.4 g/cm3, indicating a dense network. The films exhibit a relatively high coefficient of thermal expansion of around 3.2 ppm/°C, indicating a fairly short-range order in the film. Furthermore, a reversible thermally induced stress, i.e., a negligible stress hysteresis upon thermal cycling between room temperature and 400°C, has been observed in the film. From the stress response to the thermal cycling experiments, contributions from the thermal and athermal components to the net room temperature stress have been deconvoluted

Fundamental W-band InP DHBT-based VCOs with low phase noise and wide tuning range

In this paper, fundamental W-band voltage controlled oscillators (VCOs) featuring low phase noise and wide tuning range are reported. These monolithically integrated circuits (ICs) are fabricated using an InP/InGaAs DHBT technology, exhibiting cut-off frequency values of more than 250 GHz for both fT and fmax. The VCOs in differential topology consist of an oscillator core according to the negative resistance type and an ac-coupled output buffer. A first VCO version features operation frequencies ranging between 88 GHz and 100 GHz. Within this tuning range, phase noise values down to 90 dBc/Hz have been achieved at 1 MHz offset frequency, while single-ended output power values up to +4 dBm were measured, resulting in a total signal power of +7 dBm. A second VCO version shows operation frequencies between 101 GHz and 109 GHz. Within this frequency operation interval, phase noise values down to 88 dBc/Hz have been achieved at 1 MHz offset frequency, while a single-ended output power up to +2 dBm was measured, i.e. a total available signal power of +5 dBm

Multiwafer solid source phosphorus MBE on InP for DHBTs and aluminum free lasers

InP-based double heterojunction bipolar transistors (DHBTs) and aluminum free 14xx nm high power lasers were grown in a multiwafer solid source phosphorus molecular beam epitaxy system. The growth of InP, carbon-doped InGaAs, and quaternary InGaAsP was studied in detail. DHBTs display a common emitter current gain Beta of 65. Cutoff frequencies values of more than 200 GHz for both f(ind t) and f(ind max) have been achieved. Tapered diode lasers reach continuous wave output power levels of 1.5 W at room temperature

Planar InGaP/GaAs HBTs for high speed optoelectronic circuit applications

A fully planar self-aligned HBT fabrication process based on selective chemical beam epitaxial (CBE) regrowth of both the extrinsic base and subcollector layers is reported. Using this technology, cutoff frequencies of 50 and 70 GHz for fT and fmax, respectively, have been achieved for In0.49Ga0.51P/GaAs HBTs with 9 \ufffd 4 \ufffdm2 emitter-base junction area. High speed integrated circuits for lightwave communications including a 10 Gbit/s decision circuit and an 18 GHz dynamic frequency divider were successfully fabricated using these planar HBTs.NRC publication: N

Effect of emitter design on the dc characteristics of InP-based double-heterojunction bipolar transistors

NRC publication: Ye