HEMT Noise Research Articles

A SURVEY OF NOISE FIGURE RESPONSE TO OPERATING MODES IN GAN HEMT TRANSISTORS.

This paper contain experimental results for GaN HEMT noise figure and gain as functions of operating mode for L-band (1-2 GHz). It was pointed that minimum noise figure values (less than 1 dB) was measured for 2.5-5.5 V drain voltage and density current 40-80 mA/mm. Minimum noise figure (NFmin) was less than 0.G5 dB.

Influence of Spacer Thickness on the Noise Performance in InP HEMTs for Cryogenic LNAs

InP high electron mobility transistors (InP HEMTs) with different spacer thickness 1 to 7 nm in the InAlAs-InGaAs heterostructure have been fabricated and characterized at 5 K with respect to electrical dc and rf properties. The InP HEMT noise performance was extracted from gain and noise measurements of a hybrid low-noise amplifier (LNA) at 5 K equipped with discrete transistors. When biased for optimal noise operation, the LNA using 5 nm spacer thickness InP HEMTs achieved the lowest average noise temperature of 1.4 K at 4–8 GHz. The InP HEMT channel noise was estimated from the drain noise temperature which confirmed the minimum in noise temperature for the 5 nm spacer thickness InP HEMT. It is suggested that the spacer thickness acts to control the degree of real-space transfer of electrons from the channel to the barrier responsible for the observed noise variation in the cryogenic InP HEMTs.

Total-Ionizing-Dose Effects, Border Traps, and 1/f Noise in Emerging MOS Technologies

Subthreshold leakage currents and threshold-voltage shifts due to total-ionizing-dose (TID) irradiation are reviewed briefly for highly scaled devices in emerging MOS technologies. When isolation oxides of digital and analog MOS devices and ICs exhibit satisfactory performance, failure doses often are 100 krad(SiO2) to 1 Mrad(SiO2) or higher. Oxygen vacancies in SiO2 and/or high-K gate dielectrics and/or O-vacancy complexes with hydrogen are typically the dominant border traps before and after irradiation. Low-frequency noise measurements can provide significant insight into effective border-trap microstructures, densities, and energy distributions, especially when combined with complementary measurements and density-functional theory calculations. Illustrative examples are presented for past, present, and emerging MOS technologies with SiO2 and/or high-K gate dielectrics. These include FinFETs, MOS devices with alternative channels to Si, MOS devices based on 2-D materials, and SiC MOS devices. Traps in regions of MOS isolation oxides under strong gate control can also contribute to low-frequency noise, especially for multifinger, multiedge devices irradiated to high doses. The effects of defects on the 1/ $f$ noise of GaN-based HEMTs and thin metal lines are illustrated for comparison.

Modeling of Induced Gate Thermal Noise in HEMTs

We present an analytical surface potential based model for the induced thermal noise at the gate terminal in High Electron Mobility Transistors, due to gate channel coupling. Our model is applicable to any HEMT device. We also present the results of the validation of our model with experimental data from literature.

GaN HEMT noise modeling based on 50‐Ω noise factor

ABSTRACTThe extraction of a high‐frequency ivalent circuit model plays a fundamental role for the development of any emerging transistor technology. Indeed, an equivalent circuit can provide a valuable support for microwave engineers to ensure a fast and reliable optimization of both device fabrication and circuit design. As far as gallium nitride (GaN) HEMTs are concerned, research efforts have been mostly focused on determining equivalent circuits able to reproduce their large‐signal behavior. Nevertheless, an increasing amount of interest is also being devoted to noise equivalent circuits, due to the interesting GaN technology noise performance. Within this context, the purpose of the present paper is to extract and fully validate an accurate noise model for GaN HEMTs based on a simple, fast, and reliable extraction procedure. The noise model is obtained by assigning an equivalent noise temperature to each resistor of the small‐signal equivalent circuit. The accuracy of the extracted noise model is confirmed by the good agreement between measured and simulated high‐frequency noise parameters. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:937–942, 2015

1/ f Noise in GaN HEMTs grown under Ga-rich, N-rich, and NH 3-rich conditions

The magnitude of the low-frequency 1/ f noise in GaN/AlGaN HEMTs grown under Ga-rich, N-rich, and NH 3-rich conditions varies in response to hot-electron stress. Density-functional-theory (DFT) calculations show that the Ga vacancies that are responsible for the positive shift in pinch-off voltage due to electrical stress in Ga-rich and N-rich devices do not contribute significantly to the observed changes in 1/ f noise with electrical stress. The N anti-sites that cause negative shifts in pinch-off voltage in ammonia-rich devices can cause an increase in the noise magnitude after stress. DFT calculations also show that singly hydrogenated and dehydrogenated Ga–N divacancies also can contribute to the noise before and after stress, respectively. A decrease in noise magnitude is also observed in some devices after stress.

Procedure for accurate noise modelling of microwave FETs against temperature

A procedure for accurate prediction of noise parameters of microwave MESFETs/HEMTs against temperature is proposed. The error correction functions calculated for one temperature are used for efficient transistor noise parameter modelling for various device ambient temperatures, as is shown by an example of packaged HEMT noise modelling.

HEMT noise neural model based on bias conditions

Knowledge of the microwave transistor parameters at various bias conditions is often required in computer‐aided design of complex microwave low‐noise circuit. Since the measurements of noise parameters are very complex and time‐consuming, microwave circuit designers usually use the catalogues' data or noise models. The noise data that can be found in the catalogues are often limited to a few frequencies and to one or few bias points. Further, most of the existing noise models require recalculation of elements/parameters of an equivalent circuit for every bias point. Microwave HEMT transistor noise prediction based on a multilayer perceptron neural network, proposed in this paper, enables noise prediction for all operating points over a wide frequency range. Neural networks are trained to learn noise parameters' dependence on bias conditions and frequency. After network training, noise prediction for a specified bias point requires only a network response calculation without changes in the network structure.

An improved HEMT noise model for optical preamplifier design

An improved HEMT noise model for optical preamplifier design

Effect of Schottky barrier alteration on the low-frequency noise of InP-based HEMTs

For the first time the effect of increasing the Schottky barrier's Al content of InP-based InAlAs-InGaAs HEMTs from 48 to 60% on the low-frequency (LF) drain and gate current noise is investigated. It is shown that the LF gate current noise S/sub IG/(f) for the 60% case decreases by almost three decades, while the LF drain current noise S/sub IDS/(f) stays at the same level. From small coherence values, it can be concluded that drain and gate noise sources can be treated separately which facilitates the LF noise modeling of these HEMTs.

On the validity of a new extrinsic equivalent circuit including noise of HEMTs required for millimeter wave circuit design

In this paper, we propose a reliable extrinsic equivalent circuit of high electron mobility transistor (hemt) to determine both the S and noise parameters in the millimeter wave range from characterizations performed below 40 GHz. Only three extrinsic elements have to be determined instead of eight (at least) in the case of the conventional equivalent circuit. We show the validity of the proposed extrinsic equivalent circuit by S parameters and noise figure measurements up to W band (75-110 GHz).

Development of accurate on-wafer, cryogenic characterization techniques

Significant advances in the development of high electron mobility field-effect transistors (HEMT's) have resulted in cryogenic, low-noise amplifiers (LNA's) whose noise temperatures are within an order of magnitude of the quantum noise limit (h/spl nu//k). Further advances in HEMT technology at cryogenic temperatures may eventually lead to the replacement of maser and superconducting-insulator-superconducting (SIS) front-ends in the 1-100 GHz frequency band. Key to identification of the best HEMT's and optimization of cryogenic LNA's is accurate and repeatable device measurements at cryogenic temperatures. A cryogenic on-wafer noise and scattering parameter measurement system has been developed to provide a systematic investigation of HEMT noise characteristics. In addition, an improved parameter extraction technique has been developed to help understand the relationship between device structure and LNA performance.

Distributed channel model for HEMT signal and noise parameters

A new simple model for the signal and noise properties of a microwave FET or HEMT avoids the need for any explicit correlation between gate and drain noise sources by distributing the drain-to-gate capacitance and the drain noise source along the conducting channel. The new model applied to a commercial HEMT chip demonstrates a very good fit to measured scattering and noise parameter data.

Ultralow-noise pin -HEMT optical front end with spice noise modelling

Accurate modelling of HEMT noise mechanisms has been obtained using a new technique for implementing generalised noise sources in SPICE, including frequency and correlation effects. A pin-HEMT optical front end operating between 2.2 and 4.3GHz was designed, and the equivalent input noise spectral density was measured to be below 3.0pA/□(Hz) over the passband.

Wave techniques for noise modeling and measurement

The noise wave approach is applied to analysis, modeling, and measurement applications. Methods are presented for the calculation of component and network noise wave correlation matrices. Embedding calculations, relations to two-port figures-of-merit, and transformations to traditional representations are discussed. Simple expressions are derived for MESFET and HEMT noise wave parameters based on a linear equivalent circuit. A noise wave measurement technique is presented and experimentally compared with the conventional method. >

Tuned optical receivers for microwave subcarrier multiplexed lightwave systems

An analysis of tuned optical-receiver noise performance for microwave subcarrier multiplexed lightwave systems is presented. The effect of correlation between the gate and the drain HEMT noise sources and the design of tuning networks to obtain partial noise cancellation were investigated. Anoptimization algorithm is used to determine the tuning elements values for minimizing noise of 16 dB for a 60-video-channel subcarrier multiplexing (SCM) system, and 12 dB for a 120-channel system, which allows a significant increase in passive optical network distribution capacity. Design results for tuned front-end receivers encompassing the effects of p-i-n, HEMT, and SCM band parameters are presented. >

Output conductance frequency dispersion and low-frequency noise in HEMTs and MESFETs

It is reported that the high level of low-frequency noise observed in MESFETs and HEMTs in the saturation regime usually scales with the device output conductance frequency dispersion (in MESFETs) or with parallel conduction through the GaAlAs (in HEMTs). It does not seem to be directly related to output resistance frequency dispersion. The fundamental cause of output resistance dispersion in HEMTs is still unknown. Thermal feedback effects, low-frequency variations of series resistances, and trap-related effects are possibilities that require investigation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Improved performance of a cooled photoreceiver for high speed communication

An alternative method of improving photoreceiver sensitivity in a high-bit-rate optical transmission system is described. HEMTs have recently become commercially available and are known to generate mainly thermal noise and to exhibit transconductance enhancement at cryogenic temperatures. This suggests that a cooled photoreceiver with a HEMT in the first stage of the front-end amplifier could have an improved sensitivity with respect to that of room temperature operation. The DC transconductance variation between room temperature and 40 K for HEMTs of various technologies is presented. The signal-to-noise (S/N) ratios of a photoreceiver with a first-stage HEMT working at room temperature and 45 K are compared. The S/N improvement is currently about 4 dB (optical). It is found that HEMT noise generated in the frequency range considered does not seem to be of pure thermal origin. The results confirm that the proportion of MOCVD (metalorganic chemical vapor deposited) HEMTs exhibiting electrical characteristic degradation at low temperature is far less for MBE (molecular-beam epitaxial) HEMTs.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>