Prof. Nachrichtentechnik
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Fabrication and Electrical Performance of Oscillators in GaAs/GaInP-HBT MMIC Technology up to 40 GHz
(2002)
A MMIC Colpitts oscillator in push-push configuration with integrated frequency divider using InGaP/GaAs HBTs is presented. The output is taken from the second harmonic port while the fundamental signal is fed to a frequency divider by two thus providing a reference signal at one quarter of the output frequency. The MMIC VCO reaches state-of-the-art phase-noise performance in X-band down to -120dBc/Hz at 1MHz offset frequency at high output power and a tuning range of 4%.
In this paper, optimization of the loaded quality factor Q<sub>L</sub> for reflection-type heterojunction bipolar transistor (HBT) oscillators is investigated. The main result is an optimum relation between the S-parameter phases at the three transistor ports. A new design strategy for this type of oscillator is proposed. The analysis is verified by comparing several Ka-band monolithic-microwave integrated-circuit oscillators in GaAs HBT technology with different resonators. The measured loaded Q<sub>L</sub> values correspond to the measured phase noise of the circuits. At an oscillation frequency of 33 GHz, an excellent phase noise of -87 dBc/Hz at 100-kHz offset frequency is achieved over the whole tuning range.
A flip-chip packaging approach for W-band GaAs chips is presented using thin-film structures on silicon as carrier substrate. Reliability investigations indicate that, depending on bump size, the CTE mismatch is not critical and an underfiller does not provide distinctive benefits. A 77 GHz VCO GaAs-HBT MMIC is flip-chip-mounted to demonstrate validity of the packaging scheme.
A new method is presented how to characterize multiport devices using a two-port vector network-analyzer (VNA). Up to now, at least one of the port terminations had to be fully known to measure the S-parameters of the device. Our new measurement method overcomes this restriction. All of the device parameters and all of the port terminations are calculated from the device measurements.
In this paper, optimization of the loaded quality factor QL for reflection-type HBT oscillator is investigated. Main result is an optimum relation between the S parameter phases at the three transistor ports. To support this finding, a 35.5 GHz MMIC VCO phase noise better than -85 dBc/Hz at 100 kHz offset frequency is demonstrated.
Coplanar W-band push-push VCO MMICs using GaInP/GaAs HBTs are presented. One circuit operates at 77 GHz with phase noise of -92 dBc/Hz at 1 MHz offset. To our knowledge this is the first fully monolithic W-band VCO with phase noise better than -90 dBc/Hz. A second version with two varactor diodes yields an almost threefold relative tuning bandwidth.
Two differential coplanar MMIC HBT oscillators are presented, a fixed frequency and a VCO version. They provide single-ended output at the second harmonic at 38 GHz as well as differential output at 19 GHz. The oscillators show excellent phase noise performance, the fixed-frequency type reaches -95 dBc/Hz at the fundamental frequency and -89 dBc/Hz at the second harmonic, at 100 kHz offset.
In low-power applications FETs with small gate width are required. For such devices common extraction methods fail. In particular, extracting source inductance and drain pad capacitance using "cold"-FET measurements is no longer possible. We present an improved method that allows reliable extraction of extrinsic elements for small-sized FETs.
Monolithic coplanar 18 and 36 GHz oscillators with GaInP/GaAs-HBTs and on-chip resonators are presented. Measured phase-noise reaches -93 dBc/Hz and -91 dBc/Hz at 100 kHz offset for 18 and 36 GHz, respectively. These values demonstrate that GaAs-HBT oscillators yield a phase-noise performance comparable to SiGe-HBTs, with the potential for higher frequencies.
A new procedure for extracting the extrinsic capacitances of FETs is presented. It requires measurements only in the active bias regime. The method utilizes the symmetry of the intrinsic FET in the forward and reverse biased operating regime. The extraction is performed analytically and does not require any optimization.
24 GHz VCOs and frequency dividers with very low power consumption are presented. The circuits are realized as GaAs HBT MMICs. They comprise a VCO with high efficiency >17% and 12% tuning range at only 18 mW DC consumption as well as several frequency dividers. In order to minimize power consumption, the latter use the injection-locked frequency-divider (ILFD) concept. Divider ratios of 2 and 4 are realized, power consumption as low as 25 mW for a divider-by-2 is achieved. This demonstrates the capabilities of the analog concept in realizing dividers for mm-wave frequencies at DC consumption levels far below their digital counterparts
DC and RF characteristics of AlGaN/GaN HEMTs processed by 2-inch stepper lithography are presented. The devices, grown by MOVPE on 2" sapphire wafers consist of: GaN buffer, Al0.25Ga0.75 N spacer, doped Al0.25Ga0.75N supply layer, Al0.25Ga0.75N barrier, GaN cap. Refractory source and gate contacts along with mesa isolation and air bridge technology are applied. Typical values for maximum saturation current, transconductance and pinch-off voltage are: 616 m/A/mm, 203 mS/mm, -3.5 V with very good homogeneity across 2". The cut off frequencies fT and fmax are 24 and 54 GHz respectively. A standard small signal equivalent circuit model exactly describes DC- and microwave properties
AlGaN/GaN heterostructure field effect transistors (HFETs) were irradiated with 2 MeV protons, carbon, oxygen, iron and krypton ions with fluences ranging from 1 × 109 cm−2 to 1 × 1013 cm−2. DC, pulsed I–V characteristics, loadpull and S-parameters of the AlGaN HFET devices were measured before and after irradiation. In parallel, a thick GaN reference layer was also irradiated with the same ions and was characterized by X-ray diffraction, photoluminescence, Hall measurements before and after irradiation. Small changes in the device performance were observed after irradiation with carbon and oxygen at a fluence of 5 × 1010 cm−2. Remarkable changes in device characteristics were seen at a fluence of 1 × 1012 cm−2 for carbon, oxygen, iron and krypton irradiation. Similarly, remarkable changes were also observed in the GaN layer for irradiations with fluence of 1 × 1012 cm−2. The results found on devices and on the GaN layer were compared and correlated.
The effect of proton, carbon, oxygen and krypton irradiation on AlGaN HFET devices has been studied. Irradiation was performed at 68 and 120 MeV with fluences in the range from 1 × 10^7 to 1 × 10^13 cm2 . Before and after irradiation, dc and pulsed I – V characteristics, loadpull and S -parameters of the AlGaN HFET devices were measured. A thick GaN reference layer was characterized by x-ray diffraction, photoluminescence and Hall measurements before and after irradiation. Proton, carbon and oxygen irradiation show no degradation in devices while krypton irradiation shows a small change at a fluence of 1 × 10 10 cm2 in the device characteristics. The device results are correlated with the thick GaN results.
AlGaN/GaN heterostructure field effect transistors (HFETs) were irradiated with protons as well as carbon, oxygen, iron and krypton ions of high (68 and 120 MeV) and low (2 MeV) energy with fluences in the range from 1x107 to 1x1013 cm-2. High energy irradiation with protons, carbon and oxygen produced no degradation in devices while krypton irradiation at the fluence of 1x1010 cm-2 resulted in a small reduction of 2% in the transconductance. Similarly, for GaN samples irradiated with protons, carbon and oxygen at high energy no changes were seen by XRD, PL and Hall effect, while changes in lattice constant and a reduction in PL intensity were observed after irradiation with high energy krypton. Low energy irradiation with carbon and oxygen at a fluence of 5x1010 cm-2 results in small change in the device performance while remarkable changes in device characteristics are seen at a fluence of 1x1012 cm-2 for carbon, oxygen, iron and krypton irradiation. Similarly changes are also observed by XRD, PL and Hall effect for the thick GaN layer irradiated at the fluence of 1x1012 cm-2. The device results and GaN layer properties are strongly correlated.
Accurate oscillator phase-noise simulation is a key problem in MMIC design, which is not solved satisfactory so far and needs further investigation. In this paper, a Ka-band MMIC oscillator with GaInP/GaAs HBT and on-chip resonator is treated as an example. Measured phase noise reaches -90 dBc/Hz and below at 100 kHz offset. To evaluate phase-noise prediction, the circuit is simulated using different commercial simulation tools and HBT models. Considerable differences in simulation results are observed.
We report on the technology and performance of fully monolithic coplanar voltage-controlled oscillators (VCOs) with GaInP/GaAs-HBTs as the active devices. With our optimized HBT process, the parasitic base resistance R/sub B/ and extrinsic base-collector capacitance C/sub EX/ are significantly reduced. In this way, the maximum frequency of oscillation F/sub max/ is increased from 100 to 170 GHz. This allows us to realize fundamental 38 GHz-VCOs with very low phase noise. At an oscillation frequency F/sub res/=34.2/spl plusmn/0.2 GHz, the VCO reaches phase noise levels of -87 dBc/Hz @ 100 kHz and -108 dBc/Hz @ 1 MHz offset frequency, respectively. To our knowledge, these phase noise values are the lowest GaAs data for Ka-band applications reported so far.
Low phase-noise MMIC oscillators are key components for microwave and nun-wave systems. As a consequence, phase-noise measurements of these circuits have become a subject of growing interest and importance. This paper demonstrates that MMIC oscillator circuits with their relatively low Q factors are prone to specific measurement errors. Caused by a load-pull effect, the measurement system can become part of the oscillator, which yields phase-noise data significantly below reality. Special care has to be taken in order to avoid such phenomena.
High-power GaInP/GaAs HBTs with high breakdown voltage for X-band applications are presented. To demonstrate the capabilities of these devices, a simple monolithic amplifier is realized. For a single 12-finger device with 2/spl times/70 /spl mu/m/sup 2/ emitter finger size, an output power of 3.2 W at 9 GHz with 47% PAE is achieved.
This paper investigates the impact of possible parameter extraction errors caused by inaccurate definition of the calibration reference impedance of in-situ multiline TRL. Two calibration sets implemented on GaAs and Si/SiGe:C wafer processes were quantitatively analyzed. Obtained results demonstrated that for most practical cases, the desired 5%-level of confidence of extracted parameters of high-reflective devices can easily be achieved without additional efforts. Thus, implementation of the in-situ TRL into a characterization workflow of high-performance microwave devices can be significantly simplified.
The uncertainty calculation for on-wafer 1-port S-Parameter measurements due to the uncertainty of coplanar on-chip calibration standards is presented. Analytical expressions for the sensitivities are used and applied for typical fabrication tolerances of monolithic integrated on-chip structures. The method is verified for OSM calibration by means of simulations with a commercial calibration software as well as by measurements, where test-structures with artificial errors were used. In each case the analytically calculated deviation is compared to a numerical approach and good agreement is found. All results are given for a MMIC process on GaAs, but can be adopted for other technologies.