Laurent Escotte

Broadband Frequency Dispersion Small-Signal Modeling of the Output Conductance and Transconductance in AlInN/GaN HEMTs

Frequency dispersion of transconductance and output conductance in AlInN/GaN high electron mobility transistors is investigated in this paper. Broadband dispersion effects in the microwave frequency range are reported for the first time. A small-signal model is developed. Trapping effects are taken into account with parasitic electrical networks including distributed time constants. The model is compared with experimental data for several bias conditions and different types of dispersion.

SiGe HBT-Based Active Cold Load for Radiometer Calibration

An active cold load (ACL) using SiGe heterojunction bipolar transistor (HBT) has been realized at L-band for radiometer calibration. A hybrid circuit has been realized with a discrete transistor, lumped elements and microstrip transmission lines. The ACL exhibits return loss higher than 30 dB and a noise temperature less than 65 K in the L- band (1400-1427 MHz). The ambient temperature sensitivity is less than 0.3 K/°C.

Stability Analysis of an SiGe HBT-Based Active Cold Load

In this study, we report the results of short- and intermediate-term stability at L-band of an active cold load (ACL) realized with an SiGe heterojunction bipolar transistor. A noise injection radiometer has been developed to perform the measurements. A noise-equivalent delta temperature of less than 40 mK and a stability estimated to 30 mK during 90 s were obtained from Allan variance analysis. The results indicate that the variations of the ACL noise temperature correspond to the sensitivity of the measurement system. No drift was detected over one week of continuous characterization indicating that this kind of active load is very stable.

Noise characteristics of AlInN/GaN HEMTs at microwave frequencies

The microwave noise parameters measured on AlInN/GaN HEMTs devices with different gate length values are presented in this paper. 0.15-μm HEMTs achieve a maximum current density of 700 mA/mm at VGs = 0 V and a measured extrinsic transconductance of 350 mS/mm. The current gain cutoff frequency and the maximum oscillation frequency are 40 GHz and 70 GHz, respectively. At 10 (20) GHz, the device exhibits a minimum noise figure of 0.8 dB (1.8) dB with an associated power gain of 14 (8.8) dB. Below 8 GHz, the gate leakage current and a generation-recombination noise source with a very short time constant limit the noise performance.

Ka-band low noise amplifiers based on InAlN/GaN technologies

Low noise amplifiers in receivers are usually addressed by III-V (narrow bandgap) technologies: but when the receivers are subject to EM exposure or jamming, the need for protection devices before the active low noise amplifier (LNA) degrades the overall noise figure, and decreases the effective radio link budget. This vulnerability of the LNA can be overcome thanks to robust designs or robust technologies. Nitride technologies are investigated for power modules in transmitters and stand as promising solutions to avoid the use of limiters for robust low noise circuits in receivers. This work focuses on HF noise in InAlN/GaN HEMT devices and circuits for Ka-band SATCOM applications. Different versions of LNA have been designed at 30 GHz, in hybrid and MMIC technologies. For these designs, 1-stage and 3-stages LNAs have been realized; 1-stage amplifiers are designed to assess and study the stress tolerance under RF signal, whereas 3-stages LNAs are designed as demonstrators of operational module for receivers blocks (Gain>20dB featuring the lowest noise figure achievable).

InAlN/GaN HEMT technology for robust HF receivers: An overview of the HF and LF noise performances

From the first developments of Nitride technologies using AlGaN/GaN heterostructures for designing high power, high frequency HEMT devices, we now assist to the emergence of new declination with InAlN/GaN heterostructures. Considering the expected better interface quality of this last technology as a consequence of the better lattice match, and better electrical properties, these HEMT devices attract much interest for high frequency applications (transmitter for power, receiver for low noise and robustness versus jamming). Different InAlN/GaN technological developments have been studied considering their frequency and noise parameters for low noise amplifiers in Ka-band. The paper addresses two issues related to noise in InAlN/GaN HEMT devices; one concerns the study of the HF noise performance for different technological processes and for the optimized technology, whereas the second focuses on the gate and drain current LFN spectra of competing technological versions featuring good HF dynamic and noise performance.

Low-frequency noise in reverse-biased Schottky barriers on InAlN/AlN/GaN heterostructures

We present low-frequency gate noise characteristics of InAlN/AlN/GaN heterostructures grown by low-pressure metal-organic vapor phase epitaxy. The electric field in the InAlN barrier is determined from C-V measurements and is used for gate leakage current modeling. The latter is dominated by Poole-Frenkel emission at low reverse bias and Fowler-Nordheim tunneling at high electric field. Several useful physical parameters are extracted from a gate leakage model including polarizations-induced field. The gate noise fluctuations are dominated by trapping-detrapping processes including discrete traps and two continuums of traps with distributed time constants. Burst noise with several levels and time constant values is also observed in these structures. Low-frequency noise measurements confirm the presence of field-assisted emission from trap states. The 1/f noise model of McWorther is used to explain the 1/f-like noise behavior in a restricted frequency range.

Identification of the physical signatures of CDM induced latent defects into a DC¿DC converter using low frequency noise measurements.

In this paper, it is demonstrated that low frequency noise measurements are an efficient tool for the detection of latent defects induced by CDM stress in a complex circuit such as a DC-DC converter. This technique is able to detect the presence of a defect whereas classical electrical testing techniques such as Iddq or functionality test fail. In addition, a correlation between the noise signature and the nature of the defect is established. In particular, the presence of trapped charges in the oxides is clearly identified.

Generation-recombination noise, Allan variance, and low-frequency gain instabilities in microwave amplifiers

The stability of a microwave amplifier is reported in this paper. The presence of a generation-recombination noise source is investigated both in the frequency and time domains. An analytical expression of the Allan variance in the case of Lorentzian noise is originally determined in the time domain and agrees with previous work. The model is supported by experimental data realized at different temperatures which corroborates the presence of a thermally activated process.

SiGe HBT-based active cold load: Design, characterization and stability measurements

We report experimental results concerning the noise performance and the stability of an active cold load (ACL) realized with an SiGe heterojunction bipolar transistor at microwave frequency (1.4 GHz). The ACL exhibits return loss higher than 35 dB and a noise temperature less than 66 K. Stability measurements performed over 4 months with a dedicated noise injection radiometer indicates that this active load is very stable.