Microwave Noise Performance Research Articles

Investigation of cryogenic current–voltage anomalies in SiGe HBTs: Role of base–emitter junction inhomogeneities

The deviations of cryogenic collector current–voltage characteristics of SiGe heterojunction bipolar transistors (HBTs) from ideal drift-diffusion theory have been a topic of investigation for many years. Recent work indicates that direct tunneling across the base contributes to the non-ideal current in highly scaled devices. However, cryogenic discrepancies have been observed even in older-generation devices for which direct tunneling is negligible, suggesting that another mechanism may also contribute. Although similar non-ideal current–voltage characteristics have been observed in Schottky junctions and were attributed to a spatially inhomogeneous junction potential, this explanation has not been considered for SiGe HBTs. Here, we experimentally investigate this hypothesis by characterizing the collector current ideality factor and built-in potential of a SiGe HBT vs temperature using a cryogenic probe station. The temperature dependence of the ideality factor and the relation between the built-in potential as measured by capacitance–voltage and current–voltage characteristics are in good qualitative agreement with the predictions of a theory of electrical transport across a spatially inhomogeneous junction. These observations suggest that inhomogeneities in the base–emitter junction potential may contribute to the cryogenic non-idealities. This work helps to identify the physical mechanisms limiting the cryogenic microwave noise performance of SiGe HBTs.

GaN High‐Electron‐Mobility Transistors with Superconducting Nb Gates for Low‐Noise Cryogenic Applications

The successful integration of superconducting niobium (Nb) gate electrodes into cryogenic gallium nitride (GaN)‐based high‐electron‐mobility transistors (HEMTs) is reported. This is achieved through a specifically developed microfabrication process. The device's DC, microwave, and noise performances at cryogenic temperatures, down to 4 K, are studied and presented. The superconductivity of the gate is tested using DC end‐to‐end measurements. A clear superconducting state transition at a critical temperature, Tc, of ≈9.2 K is shown. This is further verified with GaN HEMTs with two gate fingers and a gate length of 0.2 μm, through the extraction and validation of a small‐signal model at T < Tc. Additionally, the superconductivity of the gate is verified for several gate widths and lengths, showing a significant reduction of the gate resistance independently of its dimensions. Finally, a comparative study of the cryogenic microwave noise performances of the GaN HEMTs with gold (Au) and Nb gates is presented. The Au‐gated device presents a competitive optimum noise temperature, Tmin‐opt, of ≈8 K at 5 GHz, demonstrating the potential of this technology for cryogenic low‐noise applications. The Nb‐gated device presents a 5 K higher Tmin‐opt, which is found to be related to the suppression of the superconductivity of the Nb gate at the optimum‐noise bias.

Noise characterisation of GaN current aperture vertical electron transistor metal‐insulated semiconductor field effect transistor with Δ‐shaped gate for low noise radio frequency amplifiers

In this article, vertical CAVET with boron-doped GaN layer as current blocking layer (CBL) for AlGaN/GaN is proposed in this study, and different electrical characteristics of the devices, such as DC (Ids − Vds), small-signal radio frequency and high-frequency microwave noise performances, are characterised using Synopsys TCAD simulations. The vertical CAVET AlGaN/GaN metal-insulated semiconductor field effect transistor (MIS-HEMT) has been found to have a high threshold VT = 6.36 V, drain saturation current, Ids,sat = 3.41 kA/cm2, reduced OFF-state current <10−12 and improved high frequency and noise performances. The findings provide insight on noise sources and provide information on how to improve GaN transistor noise performance. Its useful characterisation tool for learning more about the imperfections in advanced AlGaN/GaN MIS-HEMTs and how they evolve. A two-port noise equivalent-circuit description is used to calculate data for noise. Using data from noise and scattering parameters that have been measured, we evaluated the effect of noise sources due to gate and drain, as well as their correlation. The devices exhibit a minimum noise figure (NFmin) and an equivalent noise resistance (Rn) of 1.21 dB and 20 Ω at 20 GHz, with Vgs = 5 V and Vds = 10 V, which is small and appropriate for low-noise amplifiers with a wide bandwidth. The maximum output power density Pout of 23 dBm and the maximum PAE of 63.3% are achieved for GaN V-shaped CAVET MIS-HEMTs with Vds = 10 V at 3.12 GHz is achieved. A comparison is made between the noise performance of conventional HEMTs, MIS-HEMTs and FETs. The methods for obtaining the noise figure (NFmin) and other noise metrics are then explained and compared with those found in the literature.

Self-heating of cryogenic high electron-mobility transistor amplifiers and the limits of microwave noise performance

The fundamental limits of the microwave noise performance of high electron-mobility transistors (HEMTs) are of scientific and practical interest for applications in radio astronomy and quantum computing. Self-heating at cryogenic temperatures has been reported to be a limiting mechanism for the noise, but cryogenic cooling strategies to mitigate it, for instance, using liquid cryogens, have not been evaluated. Here, we report microwave noise measurements of a packaged two-stage amplifier with GaAs metamorphic HEMTs immersed in normal and superfluid 4He baths and in vacuum from 1.6 to 80 K. We find that these liquid cryogens are unable to mitigate the thermal noise associated with self-heating. Considering this finding, we examine the implications for the lower bounds of cryogenic noise performance in HEMTs. Our analysis supports the general design principle for cryogenic HEMTs of maximizing gain at the lowest possible power.

Influence of HfAlOx in DC, RF and Microwave Noise Performance of Dual-Channel Single-Gate InAs MOSHEMT

This paper analyzes the effect of a HfAlOx dielectric in a dual-channel (DC)single-gate (SG) metal oxide semiconductor high-electron-mobility transistor (DCSG-MOSHEMT) on improving device performance metrics. The small-signal analog/RF and noise performance of the device are explored in detail. The physics-based TCAD simulator tool is utilized to characterize the device. A peak drain current of 1.52 mA/µm is achieved due to superior sheet carrier density (ns) of 1.5×1018 cm−3 and low ON resistance. Further, a high positive threshold voltage (VT) of 0.214 V and a peak transconductance of 1.8 ms/µm is achieved with HfAlOx as the dielectric. Moreover, high cutoff frequency (fT) of 530 GHz and maximum frequency of oscillation (fmax) of 840 GHz at Vds = 0.5 V is achieved. The device exhibits a minimum noise figure of 1.32 dB at Vgs = 0.3 V and Vds = 0.5 V. With low noise over a large bandwidth and high-frequency performance, this device can be utilized to design low-noise amplifiers (LNA) for broadband applications.

Analysis of microwave noise in an enhancement-mode dual-quantum-well InAs HEMT

A systematic theoretical study is carried out on the microwave noise performance of an InAs-based dual-quantum-well double-gate high-electron mobility transistor. The proposed dual-quantum-well HEMT shows prominent small-signal analog/radiofrequency (RF) and noise performance. The results for a device with a gate length of 30 nm reveal enhancement-mode operation with a threshold voltage (Vt) of 0.146 V and high transconductance of 4.77 S/mm along with a cutoff frequency (ft) of 810 GHz and maximum oscillation frequency (fmax) of 900 GHz for Vds = 0.5 V with reduced parasitic capacitance (Cgg) of 0.003 pF/mm. The high-frequency noise of this device is estimated from the gate and drain noise spectral densities evaluated by a Green’s function method under varying bias conditions. This device shows a minimum noise figure (NFmin) of 1.62 dB in combination with an equivalent noise resistance of 972 Ω at 810 GHz for Vgs = 0.6 V and Vds = 0.5 V, which is relatively low and suitable for the design of low-noise amplifiers for use in high-frequency applications. This study shows that such an InAs HEMT with a dual-quantum-well structure is highly suitable for use in higher-frequency applications that require low noise.

Noise characterization of enhancement-mode AlGaN graded barrier MIS-HEMT devices

This paper reports a systematic theoretical study on the microwave noise performance of graded AlGaN/GaN metal-insulator semiconductor high-electron mobility transistors (MIS-HEMTs) built on an Al2O3 substrate. The HfAlOx/AlGaN/GaN MIS-HEMT devices designed for this study show an outstanding small signal analog/RF and noise performance. The results on 1 μm gate length device show an enhancement mode operation with threshold voltage, VT = + 5.3 V, low drain leakage current, Ids,LL in the order of 1 × 10−9 A/mm along with high current gain cut-off frequency, fT of 17 GHz and maximum oscillation frequency fmax of 47 GHz at Vds = 10 V. The device IV and low-frequency noise estimation of the gate and drain noise spectral density and their correlation are evaluated using a Green's function method under different biasing conditions. The devices show a minimum noise figure (NFmin) of 1.053 dB in combination with equivalent noise resistance (Rn) of 23 Ω at 17 GHz, at Vgs = 6 V and Vds = 5 V which is relatively low and is suitable for broad-band low-noise amplifiers. This study shows that the graded AlGaN MIS-HEMT with HfAlOX gate insulator is appropriate for application requiring high-power and low-noise.

Influence of temperature on transit times and microwave noise performances of SiGe HBT

The influence of temperature (300 K and 40 K) on intrinsic transit times and microwave noise performances of silicon germanium (SiGe) heterojunction bipolar transistors (HBTs) is investigated. At 300 K, we compared measured and modelled S-parameters and four noise parameters, and we found a good agreement. At 40 K, we compared measured and modelled S-parameters, and we deduced noise performances from the S-parameter measurements. The electric model includes correlated junction noise sources and a proper extraction of the transit times involved in these sources. Moreover, the microwave noise model considers all the physical phenomena that impact noise performances in SiGe HBTs. We analysed three devices having different Ge content (10%–20%, 10%–25% and 10%–30%). At 40 K, the device with 10%–25% reaches one of the lowest base transit times (τB), the lowest minimum noise figure (NFmin), and the lowest equivalent noise resistance (Rn), for operation frequencies up to the maximum device dynamic performances (f ≈ fT) These results demonstrate the excellent potential to develop cryogenic applications of SiGe HBTs.

High-Frequency Microwave Noise Characteristics of InAlN/GaN High-Electron Mobility Transistors on Si (111) Substrate

We report for the first time high-frequency microwave noise performance on 0.17-μm T-gate In 0.17 Al 0.83 N/GaN high-electron mobility transistors (HEMTs) fabricated on Si(111). The HEMTs exhibited a maximum drain current density of 1320 mA/mm, a maximum extrinsic transconductance of 363 mS/mm, an unity current gain cutoff frequency (f T ) of 64 GHz and, a maximum oscillation frequency [fmax (U)/ f max (MSG)] of 72/106 GHz. The product f max (U) × L g =12.24 GHz· μm is the highest value ever reported for InAlN/GaN HEMTs on Si substrate. At V d =4 V and V g =-2.25 V, the device exhibited a minimum noise figure (NF min ) of 1.16 dB for 10 GHz and 1.76 dB for 18 GHz. Small variation of NF min (<;0.5 dB) from 8% to 48% with I Dmax (100-636 mA/mm) was observed.

Procedure to derive analytical models for microwave noise performances of Si/SiGe:C and InP/InGaAs heterojunction bipolar transistors

We present a useful procedure to derive simplified expressions to model the minimum noise factor and the equivalent noise resistance of Si/SiGe:C and InP/InGaAs heterojunction bipolar transistors (HBTs). An acceptable agreement between models and measurements at operation frequencies up to 18 GHz and at several bias points is demonstrated. The development procedure includes all the significant microwave noise sources of the HBTs. These relations should be useful to model Fmin and Rn for state-of-the-art IV-IV and III–V HBTs. The method is the first step to derive noise analyses formulas valid for operation frequencies near the unitary current gain frequency (fT); however, to achieve this goal a necessary condition is to have access to HFN measurements up to this frequency regime.

Low-Noise Microwave Performance of AlN/GaN HEMTs Grown on Silicon Substrate

Microwave noise performance of state-of-the-art AIN/GaN high-electron-mobility transistors (HEMTs) grown on 100-mm Si substrate has been investigated. DC and RF measurements show the outstanding potential of this structure for high power millimeter-wave (mmW) applications. A maximum output current density of about 2 A/mm, together with a low gate leakage current, and a record GaN-on-Si extrinsic transconductance above 600 mS/mm are demonstrated. The current gain cutoff frequency f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">T</sub> and the maximum oscillation frequency f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> were 85 and 103 GHz, respectively, with a 0.16-μm gate length. At V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">DS</sub> = 4 V, the device exhibits a minimum noise figure (NF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> ) of 1 dB (1.8 dB) with an associated gain (G <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">A</sub> ) of 12 dB (10 dB) at 10 GHz (18 GHz) favorably comparable to the best reported GaN-on-Si HEMTs. These results show that AIN/GaN HEMTs grown on silicon substrate are promising for the integration of cost effective, low noise, and high power mmW amplifiers.

Nanometric AlGaN/GaN HEMT Performance with Implant or Mesa Isolation

AlGaN/GaN 70-nm-gate high-electron mobility transistors (HEMTs) fabricated using either ion implantation or conventional mesa isolation are compared. Although the resulting devices display comparable dc characteristics, the isolation process influences the RF and pulsed I-V characteristics. Although others have described implant-isolated GaN HEMTs, published reports focused on limited performance metrics, such as the gate leakage current. The present multiparametric study explicitly contrasts the performance of ion-implanted devices to otherwise identical mesa-isolated deep-submicrometer high-speed AlGaN/GaN HEMTs, in terms of transistor cutoff frequencies, small-signal model parameters, microwave noise performance, gate leakage currents, and large-signal pulsed I-V characteristics. We find that implant isolation can bring compelling advantages in terms of bandwidth, microwave noise performance, and tighter parametric distributions.

Sub-1-dB Noise Figure Performance of High-Power Field-Plated GaN HEMTs

In this letter, we report the state-of-the-art micro wave noise performance of discrete 0.15-μm-gate-length field plated (FP) GaN HEMTs. The FP GaN HEMTs yielded a peak fτ/f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> of 60 GHz/150 GHz at Vds = 10 V. An f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> of 230 GHz was obtained at Vds = 20 V. At 2.5 V, the source-drain bias and dc power dissipation of 200 mW/mm, a minimum noise figure (NF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> ) of 0.89 dB, and an associated gain (AG) of 11 dB were measured at 10 GHz. At 20 GHz the NF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> and AG were 1.9 and 6.2 dB, respectively. The sub-1-dB microwave noise performance at 10 GHz is the best ever reported for FP high-power GaN HEMTs, which can be attributed to their lateral scaling and deep-submicrometer gate lengths.

High Microwave-Noise Performance of AlGaN/GaN MISHEMTs on Silicon With $\hbox{Al}_{2}\hbox{O}_{3}$ Gate Insulator Grown by ALD

High microwave-noise performance is realized in AlGaN/GaN metal-insulator semiconductor high-electron mobility transistors (MISHEMTs) on high-resistivity silicon substrate using atomic-layer-deposited (ALD) Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> as gate insulator. The ALD Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /AlGaN/GaN MISHEMT with a 0.25- ¿m gate length shows excellent microwave small signal and noise performance. A high current-gain cutoff frequency <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">fT</i> of 40 GHz and maximum oscillation frequency <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">max</sub> of 76 GHz were achieved. At 10 GHz, the device exhibits low minimum-noise figure (NF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> ) of 1.0 dB together with high associate gain ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Ga</i> ) of 10.5 dB and low equivalent noise resistance ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Rn</i> ) of 29.2 ¿. This is believed to be the first report of a 0.25-¿m gate-length GaN MISHEMT on silicon with such microwave-noise performance. These results indicate that the AlGaN/GaN MISHEMT with ALD Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> gate insulator on high-resistivity Si substrate is suitable for microwave low-noise applications.

Low microwave noise of AlGaN/GaN HEMTs fabricated on SiCopSiC substrates

Low microwave noise performance of AlGaN/GaN HEMTs fabricated on MOCVD epitaxial structures grown on composite substrates (SiCopSiC) is reported. They are made of a thin SiC single-crystal layer transferred on top of a thick polycrystalline SiC wafer. The transistor fabrication process is similar to the one developed for AlGaN/GaN devices on SiC substrate. A minimum noise figure of 0.12 dB with an associated gain of 14.8 dB at 3 GHz is found, showing the capability of gallium-nitride based devices for low noise microwave applications in the S-band.

Improved Microwave Noise Performance by SiN Passivation in AlGaN/GaN HEMTs on Si

Effects of silicon nitride (SiN) surface passivation by plasma enhanced chemical vapor deposition (PECVD) on microwave noise characteristics of AlGaN/GaN HEMTs on high-resistivity silicon (HR-Si) substrate have been investigated. About 25% improvement in the minimum noise figure (NF min) (0.52 dB, from 2.03 dB to 1.51 dB) and 10% in the associate gain (G a) (1.0 dB, from 10.3 dB to 11.3 dB) were observed after passivation. The equivalent circuit parameters and noise source parameters (including channel noise coefficient (P), gate noise coefficient (R), and their correlation coefficient (C)) were extracted. P, R and C all increased after passivation and the increase of C contributes to the decrease of the noise figure. It was found that the improved microwave small signal and noise performance is mainly due to the increase of the intrinsic transconductance (g m0) and the decrease of the extrinsic source resistance (R s).

High-Performance 0.1-$\mu\hbox{m}$ Gate AlGaN/GaN HEMTs on Silicon With Low-Noise Figure at 20 GHz

The realization of high-performance 0.1-mum gate AlGaN/GaN high-electron mobility transistors (HEMTs) grown on high-resistivity silicon substrates is reported. Our devices feature cutoff frequencies as high as fT = 75 GHz and fMAX = 125 GHz, the highest values reported so far for AlGaN/GaN HEMTs on silicon. The microwave noise performance is competitive with results achieved on other substrate types, such as sapphire and silicon carbide, with a noise figure F = 1.2-1.3 dB and an associated gain Gass = 8.0-9.5 dB at 20 GHz. This performance demonstrates that GaN-on-silicon technology is a viable alternative for low-cost millimeter-wave applications.

The impact of post gate annealing on microwave noise performance of AlGaN/GaN HEMTs

The effects of post gate annealing on microwave noise performance of AlGaN/GaN HEMTs on SiC substrate were investigated. The results show that post Schottky gate annealing under an optimized condition, 400°C for 10min in N2 ambient, can increase the current driving capability, reduce gate leakage current, and improve the microwave noise performance. Specifically, the maximum extrinsic transconductance increased from 223mS/mm to 233mS/mm. The 1mA/mm gate leakage current at Vgs=−30V reduced to 4nA/mm. Before annealing, the device exhibited a minimum noise figure of 0.99dB at 4GHz. It decreased to 0.63dB and the associated gain increased from 13.2dB to 17.4dB at the mean time. The change is even more significant under high current operation. At 4GHz, the 4.90dB NFmin at Ids of 670mA/mm decreased more than 3dB to 1.12dB. Based on a simple noise model, the improvement of the microwave noise performance is attributed to the significant decrease of the gate leakage current.

An evolution algorithm for noise modeling of HEMT’s down to cryogenic temperatures

The implementation of an Evolution Algorithm (EA) for the cryogenic noise modeling of microwave devices has been the object of the present work. Several approaches exist to treat the modeling issue as far as advanced microwave transistors are concerned. The aim of such procedures is mostly oriented to extract a linear equivalent circuit including noise performance that allows to reproduce the global device behavior in a small signal regime. In the present paper, the authors show how EA’s can be employed to solve the noise modeling problem according to a black-box approach. The application refers to the simulation of the Noise Parameters of High Electron Mobility Transistors (HEMT) in the 6-18 GHz frequency range and down to cryogenic temperatures (90K) compared with experimental data. The quality of results indicates that EA techniques represent a truly alternative way to determine the microwave noise performance of HEMT devices, thus furnishing a flexible tool to support CAD of high sensitivity – ultra high speed circuits.

Temperature dependent study on the microwave noise performance of metamorphic InP/InGaAs heterojunction bipolar transistors

In this study, a detailed characterization on the microwave noise performance of high gain metamorphic heterojunction bipolar transistor (MHBT) in the temperature range of 300 K to 380 K is performed. The results are compared between the MHBT and the referenced lattice-matched InP HBT (LHBT) devices. The minimum noise figure (NF min) versus frequency in the range of 2 to 20 GHz at different temperatures for a 1.6 × 20 μm 2 HBTs are measured. The experimental results show that the MHBT exhibits a slightly larger variation in NF min compared to lattice-matched HBTs. Even though the MHBTs may have much higher thermal resistance, this may not significantly affect the device microwave noise performance.