Double Channel High Electron Mobility Transistors Research Articles

NPDC structure double-channel N-polar E-mode GaN HEMTs: Innovations in enhancing RF and DC performance and mitigating trap effects

—High-electron-mobility transistors (HEMTs) based on gallium nitride (GaN) are favored for their exceptional performance in high-power and high-frequency applications. However, developing dual-channel HEMTs presents challenges due to spontaneous polarization effects and design complexities. This study introduces a novel N-polar E-mode GaN HEMT with a dual-channel structure, featuring recessed drain-source regions and non-alloyed ohmic contacts. TCAD simulations provide theoretical insights and optimization strategies for these structures, focusing on the combination of N-polar GaN and ultra-wide bandgap AlN barrier layers. The optimized device demonstrates a threshold voltage of +1.08 V and a 45.9 % increase in current density. The N-polar double-channel HEMT (NPDC-HEMT) exhibited a 55.75 % improvement in peak transconductance, with Ft increasing from 13.3 GHz to 30.1 GHz and Fmax from 63.7 GHz to 65.9 GHz. Further enhancement was achieved in the T-gate variant (NPDC-T-HEMT), with Ft reaching 52.6 GHz and Fmax 94.4 GHz. The dual-channel design effectively mitigated short-channel effects and current collapse, demonstrating the potential for high-power RF applications.

Deep insight of inter-channel coupling in AlGaN/GaN double channel HEMT and its application in C-ERB2 sensing

AlGaN/GaN Double Channel High Electron Mobility Transistors (DCHEMTs) have emerged as promising biosensors, leveraging the unique properties of inter-channel coupling. This paper investigates the influence of mole fraction variations in the AlGaN layer on inter-channel coupling and explores its implications for C-ERB2 biosensing. The study reveals the potential of inter-channel coupling to enhance sensitivity in biosensing applications, particularly for detecting C-ERB2, a crucial protein associated with various cancers. The device architecture, simulation models, electrostatics, and sensitivity analysis are comprehensively examined. The findings underscore the significance of inter-channel coupling in optimizing biosensor performance, offering valuable insights for the advancement of biosensing technologies.

Acoustic and optical plasmons excitation in double-channel AlGaN/GaN HEMT under asymmetric boundaries

We have simulatively studied the electrical excitation of acoustic and optical plasmons in double-channel AlGaN/GaN high electron mobility transistors (HEMT) under asymmetric boundaries. By solving the self-consistent hydrodynamic model with Maxwell’s equations, it is found that the drift plasmons are excited in the bilayer 2DEGs under asymmetric boundaries. The oscillation intensity in a bilayer system is much stronger than that in a monolayer 2DEG system because of the simultaneous excitation of the fundamental and the second harmonic components. The fundamental component always corresponds to the acoustic plasmon, while the optical plasmon can be excited when it is resonant with the second harmonic of the acoustic plasmon. Because of the out-of-phase properties of the acoustic plasmons, their radiated power is limited by the current cancellation. On the other hand, as the optical plasmons are excited, the radiated powers are much higher than those of the single channel HEMT due to the in-phase currents generated in the double layers. The effects of different parameters such as gate lengths, 2DEG spacings, and electron concentrations on plasmon excitations and THz emissions of double-channel HEMTs are analyzed in detail. The numerical results provide a more powerful terahertz radiation mechanism in double-channel HEMT compared with the Dyakonov–Shur instability in traditional single-channel HEMT.

Numerical investigation of the performance of AlGaN/GaN/BGaN double-gate double-channel high electron mobility transistor

<p><span>In this work, we examine the direct-current (DC) behavior and the radio-frequency (RF) performance of both single-gate simple-channel (SGSC), single-gate double-channel (SGDC) and double-gate double-channel (DGDC) AlGaN/GaN/BGaN high electron mobility transistor (HEMT) with BGaN back-barriers consist of 250 nm gate length. Using Technologie Computer Aided Design (TCAD) Silvaco, our isothermal simulation results reveal that the proposed structure of double-gate double-channel HEMT with BGaN back-barriers (DGDCBB HEMT) increases electron concentration and consequently the saturation drain current, breakdown voltage, the transconductance. On the other hand, decreases the gate leakage current compared to a conventional HEMT and to a double-channel HEMT back-barriers. Furthermore, the proposed double-gate double-channel back-barrier HEMT device shows good cutoff frequency (94 GHz) and a maximum oscillation frequency (170 GHz). These results suggest that double-gate double channel HEMT back-barriers could be useful for high-frequency and high-power microwave applications.</span></p>

High performance InGaN double channel high electron mobility transistors with strong coupling effect between the channels

In this paper, high performance InGaN double channel (DC) high electron mobility transistors (HEMTs) are proposed and systematically investigated. Due to the coordination of double InGaN channels, a large maximum drain current density and a distinct double-hump feature of the transconductance and frequency performance are achieved. More importantly, it is revealed that the coupling effect between the two InGaN channels is much stronger than that of the conventional GaN DC HEMTs. This characteristic leads to a remarkable enhancement in the gate voltage swing, indicating the excellent linearity of the InGaN DC HEMTs at both dc and rf conditions. Benefiting from the enhanced electron confinement in InGaN channels, the fabricated HEMTs show a low off state drain leakage current of 0.26 μA/mm and a high on/off current ratio (Ion/Ioff) of 5.1 × 106. In addition, the desirable current collapse and breakdown characteristics are also obtained. This work convincingly demonstrates the great potential and practicality of the InGaN DC HEMTs for high power and high bandwidth applications.

TCAD Simulation for Nonresonant Terahertz Detector Based on Double-Channel GaN/AlGaN High-Electron-Mobility Transistor

We propose a nonresonant terahertz (THz) detector based on double-channel (DC) GaN/AlGaN high-electron-mobility transistor (HEMT) utilizing a technology computer-aided design platform. The hydrodynamic model is simplified as the drift-diffusion model for nonresonant THz detection simulation. Dependence of THz photoresponse on various structure parameters of the detector is analyzed by simulation. The two typical metrics, responsivity and noise equivalent power (NEP), are theoretically calculated for the optimization of the structure parameters. The optimized responsivity and NEP reach 5.8 kV/W and 50 pW/Hz0.5 at the same gate voltage, respectively, and a minimum NEP of 20 pW/Hz0.5 is obtained. The comparison between our simulation results and the experiment data of single-channel HEMT detector proves that the DC HEMT detector shows an excellent THz detection performance.

Analysis of plasma-modes of a gated bilayer system in high electron mobility transistors

We present rigorous analytical and computational models to study the plasma-waves in a gated-bilayer system present in a double-channel high electron mobility transistor. By analytically deriving the dispersion relations, we have identified the optical and acoustic modes in such systems. We find that the presence of the metal gate selectively modifies the optical plasmons of an ungated-bilayer, while the acoustic plasmons remain largely unchanged. Analysis shows that these modified optical plasmons could be advantageous for resonant and non-resonant plasma-wave devices. The paper further serves to verify our analytical formulae using a full-wave hydrodynamic numerical solver, based on finite difference time domain algorithm. Using the solver, we examine these modes in the gated/ungated bilayers under a plane wave excitation. We observe that, most incident power couples to the optical mode for such an excitation. Nevertheless, acoustic modes can also be excited, if the discontinuity dimensions are optimized accordingly. These observations are also explained using 2D field-plots for the first time, thus providing intuitive understanding of the plasmon excitation in the bilayers.

Pulsed metal organic chemical vapor deposition of InAlN-based heterostructures and its application in electronic devices

As a promising group III-nitride semiconductor material, InAlN ternary alloy has been attracted increasing interest and widespread research efforts for optoelectronic and electronic applications in the last 5 years. Following a literature survey of current status and progress of InAlN-related studies, this paper provides a brief review of some recent developments in InAlN-related III-nitride research in Xidian University, which focuses on innovation of the material growth approach and device structure for electronic applications. A novel pulsed metal organic chemical vapor deposition (PMOCVD) was first adopted to epitaxy of InAlN-related heterostructures, and excellent crystalline and electrical properties were obtained. Furthermore, the first domestic InAlN-based high-electron mobility transistor (HEMT) was fabricated. Relying on the PMOCVD in combination with special GaN channel growth approach, high-quality InAlN/GaN double-channel HEMTs were successfully achieved for the first time. Additionally, other potentiality regarding to AlGaN channel was demonstrated through the successful realization of nearly lattice-matched InAlN/AlGaN heterostructures suitable for high-voltage switching applications. Finally, some advanced device structures and technologies including excellent work from several research groups around the world are summarized based on recent publications, showing the promising prospect of InAlN alloy to push group III-nitride electronic device performance even further.

Trap states in InAlN/AlN/GaN-based double-channel high electron mobility transistors

We present a detailed analysis of trap states in InAlN/AlN/GaN double-channel high electron mobility transistors grown by pulsed metal organic chemical vapor deposition. By frequency dependent conductance measurements, trap densities and time constants at both InAlN/AlN/GaN interfaces were determined. Two types of traps, with a high density of up to ∼1014 cm−2 eV−1, were observed existing at the higher InAlN/AlN/GaN interface. On the other hand, the density dramatically decreased to ∼1012 cm−2 eV−1 for traps located at lower InAlN/AlN/GaN interface on which a low-temperature grown GaN (LT-GaN) layer was deposited. Additionally, photo-assisted capacitance-voltage measurements were performed to estimate deep-level defects, yielding a low density of 1.79 × 1011 cm−2 acting as negative fixed charges at the LT-GaN and lower InAlN interface.

Double-Channel AlGaN/GaN High Electron Mobility Transistor With Back Barriers

We have developed a double-channel high electron mobility transistor with back barriers for carrier confinement. We have observed that the double-channel devices may suffer from the lack of gate control particularly for the lower channel. However, the problem can be contained by using a suitable back barrier for the lower channel. The double-channel back-barrier devices show good current gain and power gain cutoff frequencies. These devices can be operated with excellent gain linearity up to a larger value for input power and frequency.

Fabrication and characterization of InAlN/GaN-based double-channel high electron mobility transistors for electronic applications

In our previous work [J. S. Xue et al., Appl. Phys. Lett. 100, 013507 (2012)], superior electron-transport properties are obtained in InAlN/GaN/InAlN/GaN double-channel (DC) heterostructures grown by pulsed metal organic chemical vapor deposition (PMOCVD). In this paper, we present a detailed fabrication and systematic characterization of high electron mobility transistors (HEMTs) fabricated on these heterostructures. The device exhibits distinct DC behavior concerning with both static-output and small-signal performance, demonstrating an improved maximum drain current density of 1059 mA/mm and an enhanced transconductance of 223 mS/mm. Such enhancement of device performance is attributed to the achieved low Ohmic contact resistance as low as 0.33 ± 0.05 Ω·mm. Moreover, very low gate diode reverse leakage current is observed due to the high quality of InAlN barrier layer deposited by PMOCVD. A current gain frequency of 10 GHz and a maximum oscillation frequency 21 GHz are also observed, which are comparable to the state-of-the-art AlGaN/GaN-based DC HEMT found in the literature. The results demonstrate the great potential of PMOCVD for application in InAlN-related device’s epitaxy.

2DEG properties in InGaN/InN/InGaN‐based double channel HEMTs

AbstractThis paper describes the 2DEG properties of InGaN/InN/InGaN double channel high electron mobility transistor (DHEMT). These include an in‐depth theoretical investigation of 2DEG sheet carrier concentration and mobility. The 2DEG mobility is calculated using ensemble Monte Carlo taking into account all relevant scatterings. The calculated sheet carrier concentration reaches as high as 1.77×1014 cm‐2 for DHEMT. While for single channel high electron mobility transistor (SHEMT) the calculated sheet carrier concentration was found to be 7.06×1013 cm‐2. The maximum total 2DEG mobility is found to be around 12×104 and 8×104 cm2V‐1s‐1, respectively, for DHEMT and SHEMT for a sheet carrier concentration of ns = 5×1012 cm‐2 at 77 K. Thus, the 2DEG sheet carrier concentration and mobility for dual channel is higher than conventional single channel HEMTs. The high values of 2DEG sheet carrier concentration and mobility strongly suggest that the InGaN/InN/InGaN based double channel HEMT is very promising for the fabrication of high performance high speed device (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

AlGaN/GaN double-channel HEMT

The fabrication of AlGaN/GaN double-channel high electron mobility transistors on sapphire substrates is reported. Two carrier channels are formed in an AlGaN/GaN/AlGaN/GaN multilayer structure. The DC performance of the resulting double-channel HEMT shows a wider high transconductance region compared with single-channel HEMT. Simulations provide an explanation for the influence of the double-channel on the high transconductance region. The buffer trap is suggested to be related to the wide region of high transconductance. The RF characteristics are also studied.

A comparative study on single and double channel AlGaN/GaN high electron mobility transistor

AbstractWe present a numerical investigation on the DC and AC characteristics of AlGaN/GaN single (SCHEMT) and double channel high electron mobility transistors (DCHEMT) using the APSYS simulation program. The simulation results indicate that the DCHEMT has a slightly wider range of transconductance and cut‐off frequency for device operation at high current levels than SCHEMT. Besides, we also examine the effect of barrier layer thickness between the two channels in DCHEMT on the transconductance profile. It is found that the operation range of transconductance can be tailored by adjusting the barrier layer thickness. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

AlGaN-GaN Double-Channel HEMTs

We present the design, fabrication, and characterization of AlGaN-GaN double-channel HEMTs. Two carrier channels are formed in an AlGaN-GaN-AlGaN-GaN multilayer structure grown on a sapphire substrate. Polarization field in the lower AlGaN layer fosters formation of a second carrier channel at the lower AlGaN-GaN interface, without creating any parasitic conduction path in the AlGaN barrier layer. Unambiguous double-channel behaviors are observed at both dc and RF. Bias dependent RF small-signal characterization and parameter extraction were performed. Gain compression at a high current level was attributed to electron velocity degradation induced by interface scattering. Dynamic IV measurement was carried out to analyze large-signal behaviors of the double-channel high-electron mobility transistors. It was found that current collapse mainly occurs in the channel closer to device surface, while the lower channel suffers minimal current collapse, suggesting that trapping/detrapping of surface states is mainly responsible for current collapse. This argument is supported by RF large-signal measurement results.

Multicarrier characterization method for extracting mobilities and carrier densities of semiconductors from variable magnetic field measurements

A simple, practical method is described to extract the carrier concentration and mobility of each component of a multicarrier semiconductor system (which may be either a homogeneous or multilayered structure) from variable magnetic field measurements. Advantages of the present method are mainly due to the inclusion of both the longitudinal and transverse components of the conductivity tensor and normalization of these quantities with respect to the zero-field longitudinal component of the conductivity tensor. This method also provides a simple, direct criterion by which one can easily determine whether the material under test is associated with a one-carrier or multicarrier conduction. The method is demonstrated for a simple one-carrier system [GaAs single-channel high-electron-mobility-transistor (HEMT) structure] and two multicarrier systems (an InGaAs-GaAs double-channel HEMT structure and two types of carriers present in an InGaAs single-channel HEMT structure). The analysis of the experimental data obtained on these samples demonstrates the utility of the method presented here for extracting carrier concentrations and mobilities in advanced semiconductor structures.