Heterojunction High Electron Mobility Transistors Research Articles

Damage Effects and Mechanisms of High-Power Microwaves on Double Heterojunction GaN HEMT

In this paper, simulation modeling was carried out using Sentaurus Technology Computer-Aided Design. Two types of high electron mobility transistors (HEMT), an AlGaN/GaN/AlGaN double heterojunction and AlGaN/GaN single heterojunction, were designed and compared. The breakdown characteristics and damage mechanisms of the two devices under the injection of high-power microwaves (HPM) were studied. The variation in current density and peak temperature inside the device was analyzed. The effect of Al components at different layers of the device on the breakdown of HEMTs is discussed. The effect and law of the power damage threshold versus pulse width when the device was subjected to HPM signals was verified. It was shown that the GaN HEMT was prone to thermal breakdown below the gate, near the carrier channels. A moderate increase in the Al component can effectively increased the breakdown voltage of the device. Compared with the single heterojunction, the double heterojunction HEMT devices were more sensitive to Al components. The high domain-limiting characteristics effectively inhibited the overflow of channel electrons into the buffer layer, which in turn regulated the current density inside the device and improved the temperature distribution. The leakage current was reduced and the device switching characteristics and breakdown voltage were improved. Moreover, the double heterojunction device had little effect on HPM power damage and high damage resistance. Therefore, a theoretical foundation is proposed in this paper, indicating that double heterojunction devices are more stable compared to single heterojunction devices and are more suitable for applications in aviation equipment operating in high-frequency and high-voltage environments. In addition, double heterojunction GaN devices have higher radiation resistance than SiC devices of the same generation.

Performance analysis of gallium nitride-based DH-HEMT with polarization-graded AlGaN back-barrier layer

In this paper, polarization-graded AlGaN back-barrier nanolayer has been introduced to improve the DC and RF parameters of gallium nitride-based high electron mobility transistors (HEMT). To explore the characteristics, both graded and non-graded double heterojunction high electron mobility transistor (DH-HEMT) structures are optimized using SILVACO-ATLAS physical simulator. Enhanced DC and RF parameters have been observed in the optimized graded DH-HEMT. In this paper, we have also studied the development of the quantum wells at the AlGaN/GaN interfaces due to the conduction band discontinuity in both structures.

Qualitative Analysis & Advancement of Asymmetric Recessed Gates with Dual Floating Material GaN HEMT for Quantum Electronics

The Impact of Aluminium nitride (AlN) Spacer, Gallium Nitride (GaN) Cap Layer, Front Pi Gate (FG) and Back Pi Gate(BG), High K dielectric material such as Hafnium dioxide(HfO2), Aluminium Oxide (Al2O3), Silicon nitride (Si3N4) on Aluminium Galium Nitride/ Gallium Nitride (AlGaN/GaN), Heterojunction High Electron Mobility Transistor (HEMT) of 6nm(nanometer) technology is simulated and extracted the results using the Silvaco Atlas TCAD tool. The importance of High K dielectric materials like Al2O3 and Si3N4 are studied for the proposal of GaN HEMT. AlN, GaN Cap Layers, and High K Dielectric material are layered one on another to overcome the conventional transistor draw backs like surface defects, scattering of the electron, and less mobility of electron. Hot electron effect is overcome by Pi type gate. Therefore, by optimizing the HEMT structure the abilities for certain devices are converted to abilities. The dependency on DC characteristics and RF characteristics due to GaN Cap Layers, Multi gate (FG &BG), and High K Dielectric material is established. Further Compared Single Gate (SG) Passivated HEMT, Double Gate (DG) Passivated HEMT, Double Gate Triple(DGT) Tooth Passivated HEMT, High K Dielectric Front Pi Gate (FG) and Back Pi Gate (BG) Nanowire HEMT. It is observed that there is an increased Drain Current (Ion) of 5.92(A/mm), low Leakage current(Ioff) 5.54E-13 (A) of Transconductance (Gm) of 3.71(S/mm), Drain Conductance (Gd) of 1.769(S/mm), Cutoff frequency(fT) of 743 GHz Maximum Oscillation frequency (Fmax) 765 GHz, Minimum Threshold Voltage (Vth) of -4.5V, On Resistance (Ron)of 0.40(Ohms) at Vgs =0V. These outstanding characteristics and transistor structure of proposed HEMT and materials involved to apply for upcoming generation High-speed GHz frequency applications.

Performance Analysis of High-K Dielectric Heterojunction High Electron Mobility Transistor for RF Applications

Performance Analysis of High-K Dielectric Heterojunction High Electron Mobility Transistor for RF Applications

A Difference-Microvariation Solution and Analytical Model for Generic HEMTs

An analytical dc model of AlGaN/GaN and AlGaAs/GaAs-based high-electron mobility transistors (HEMTs) is proposed, while the charge accumulated in the barrier layer at high gate biases voltage is taken into account. To break through the bottleneck problem of solving model accurately and efficiently, an improved difference-microvariation (DM) explicit algorithm is developed to solve the complex transcendental equations of Fermi level and surface potential in the physical model, including two important subbands in a triangular potential well. Compared with the existing analytical surface potential-based algorithms, the DM algorithm quantifies the high-order component and obtains a more precise solution. The universality and accuracy of the model and DM solutions are verified against numerical results and experimental data under a wide range of operation region, which proves that the model combined with DM method is expected to become the suitable simulation tools for generic heterojunction HEMTs.

Enhancing the Sensitivity of GaN High Electron-Mobility Transistors-Based pH Sensor by Dual Function of Monolithic Integrated Planar Multi-Channel and Ultraviolet Light

In order to realize high-sensitivity real-time monitoring of acid–base neutral solutions in the industrial field, it is very important to study how to improve the sensitivity of a pH sensor. Herein, the sensitivity of the pH sensor was improved by using both monolithic integrated planar multi-channel and photoconductive properties of gallium nitride (GaN) high electron-mobility transistors (HEMTs) as a core of the pH sensor. The sensitive area of aluminum gallium nitride/gallium nitride (Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.25</sub> Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.75</sub> N/GaN) heterojunction HEMT channel surface was increased, and the channel effective resistance was reduced by planar multi-channels. And the photogenerated current was generated by 365-nm ultraviolet (UV) light based on the photoconductive effect. This investigation mainly shows as the sensitivity of the tri-channel was 37.04 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> /pH, which increased 30 times compared with that of the single-channel device under the dual action of planar multi-channel and 365-nm UV light coupling in potassium hydrogen phthalate, mixed phosphate, and borax pH correction buffer solutions. The concept of using the GaN HEMT-based pH sensor for direct quantification of pH values in waste water provides a simple and high-performance method for industrial applications.

Design of GaN/AlGaN Heterojunction High Electron Mobility Transistor with Back Gate and Intrisnic Spacer Layer

Design of GaN/AlGaN Heterojunction High Electron Mobility Transistor with Back Gate and Intrisnic Spacer Layer

Investigation of Influence of SiN and SiO2 Passivation in Gate Field Plate Double Heterojunction Al0.3Ga0.7N/GaN/Al0.04Ga0.96N High Electron Mobility Transistors

This research article reports the operational characteristics of gate field plate double heterojunction (DH) high electron mobility transistors (HEMTs) using SiN (SiO2) passivation techniques. The proposed HEMT exhibits 496 (292) V breakdown voltage (VBR) for LG (gate-length) = 0.25 μm, LGD (drain-gate distance) = 3.2 μm and 1 μm field plate length HEMT. The n + GaN source/drain regions with SiN (SiO2) passivation AlGaN/GaN/AlGaN HEMT delivered 1.4 (1.3) A/mm peak drain current density (Ids), 540 (550) mS/mm gm (transconductance), fT/fMAX of 54/198 (62/252) GHz, and the sub-threshold drain leakage current of 4 × 10−13 (1 × 10−11) A/mm. The high Johnson figure of merit (JFoM = fT × VBR) of 28.76 (19.27) THz.V and excellent VBR × fMAX product of 90.27 (73.29) THz.V demonstrates the great potential of the optimized gate field plate DH-HEMTs structure for U and V band high power microwave electronics.

The Study on Structural and Photoelectric Properties of Zincblende InGaN via First Principles Calculation

In this paper, the structure and photoelectric characteristics of zincblende InxGa1−xN alloys are systematically calculated and analyzed based on the density functional theory, including the lattice constant, band structure, distribution of electronic states, dielectric function, and absorption coefficient. The calculation results show that with the increase in x, the lattice constants and the supercell volume increase, whereas the bandgap tends to decrease, and InxGa1−xN alloys are direct band gap semiconductor materials. In addition, the imaginary part of the dielectric function and the absorption coefficient are found to redshift with the increase in indium composition, expanding the absorption range of visible light. By analyzing the lattice constants, polarization characteristics, and photoelectric properties of the InxGa1−xN systems, it is observed that zincblende InxGa1−xN can be used as an alternative material to replace the channel layer of wurtzite InxGa1−xN heterojunction high electron mobility transistor (HEMT) devices to achieve the manufacture of HEMT devices with higher power and higher frequency. In addition, it also provides a theoretical reference for the practical application of InxGa1−xN systems in optoelectronic devices.

Effect of AlxGa1−xN buffer layer on the structural and electrical properties of AlGaN/GaN/AlxGa1−xN double heterojunction high electron mobility transistor structures

In this paper, the authors report the effect of the AlxGa1−xN buffer layer on the structural and electrical properties of an AlGaN/GaN/AlxGa1−xN double heterojunction high electron mobility transistor (HEMT). As the Al composition of the buffer layer increased, the two-dimensional electron gas (2DEG) confinement of the channel was shown to improve, which was confirmed by the simulation. The AlGaN buffer HEMT showed improved structural characteristics, such as the surface morphology, crystal quality, and interface roughness compared with the conventional HEMT with a C-doped GaN buffer. A slight decrease in 2DEG characteristics owing to the negative polarization charge was observed. However, in the breakdown voltage characteristics, comparable results were obtained as 652 V for the HEMT with C-doped GaN, 624 V for the HEMT with an Al0.044Ga0.956N buffer, and 642 V for the HEMT with an Al0.088Ga0.912N buffer, although the AlGaN buffers were not doped for semi-insulating.

Investigation of ultra-scaled AlN/GaN/InGaN double heterojunction HEMT for high-frequency applications

ABSTRACT In this paper, we report the high-frequency performance of ultra-scaled AlN/GaN/InGaN double heterojunction high electron mobility transistor (HEMT) on SiC. Industry standard Synopsys Sentaurus TCAD is used for device simulation. The proposed double heterojunction AlN/GaN/InGaN HEMT device with regrown n+ InGaN/GaN ohmic contacts exhibited a record fT/fmax of 451/448 GHz for 20 nm gate length. The double heterojunction HEMT with GaN cap layer uplift the breakdown voltage (21 V) of deeply scaled device structure. The presented high-frequency performance of AlN/GaN HEMT will be the most suitable candidate for next-generation high speed and high power microwave electronics.

Improved quasi‐physical zone division model with analytical electrothermal Ids model for AlGaN/GaN heterojunction high electron mobility transistors

AbstractAn accurate analytical electrothermal drain current (Ids) model for AlGaN/GaN HEMTs is presented in this letter. The model is implemented into our recently proposed quasi‐physical zone division (QPZD) model for demonstration purpose. Compared with the original QPZD model, its electrothermal characteristics are enhanced by involving more fundamental temperature dependent elements. In addition, these elements are derived analytically based on physical mechanisms instead of former pure empirical fitting method. Thus, the extracted parameter values are more close to intrinsic values. An in house 0.15‐μm GaN HEMT is used for validation. Compared with the measured data at a wide ambient temperature range (245‐390 K), this electrothermal model demonstrates good accuracy to predict the DC characteristics and RF performances of GaN HEMTs.

Growth and characterization of AlGaN/GaN/AlGaN double-heterojunction high-electron-mobility transistors on 100-mm Si(111) using ammonia-molecular beam epitaxy

To improve the confinement of two-dimensional electron gas (2DEG) in AlGaN/GaN high electron mobility transistor (HEMT) heterostructures, AlGaN/GaN/AlGaN double heterojunction HEMT (DH-HEMT) heterostructures were grown using ammonia-MBE on 100-mm Si substrate. Prior to the growth, single heterojunction HEMT (SH-HEMT) and DH-HEMT heterostructures were simulated using Poisson-Schrödinger equations. From simulations, an AlGaN buffer with “Al” mole fraction of 10% in the DH-HEMT was identified to result in both higher 2DEG concentration (∼1013 cm−2) and improved 2DEG confinement in the channel. Hence, this composition was considered for the growth of the buffer in the DH-HEMT heterostructure. Hall measurements showed a room temperature 2DEG mobility of 1510 cm2/V.s and a sheet carrier concentration (ns) of 0.97 × 1013 cm−2 for the DH-HEMT structure, while they are 1310 cm2/V.s and 1.09 × 1013 cm−2, respectively, for the SH-HEMT. Capacitance-voltage measurements confirmed the improvement in the confinement of 2DEG in the DH-HEMT heterostructure, which helped in the enhancement of its room temperature mobility. DH-HEMT showed 3 times higher buffer break-down voltage compared to SH-HEMT, while both devices showed almost similar drain current density. Small signal RF measurements on the DH-HEMT showed a unity current-gain cut-off frequency (fT) and maximum oscillation frequency (fmax) of 22 and 25 GHz, respectively. Thus, overall, DH-HEMT heterostructure was found to be advantageous due to its higher buffer break-down voltages compared to SH-HEMT heterostructure.

Effect of inserted AlN layer on the two-dimensional electron gas in AlxGa1-xN/AlN/GaN

This paper investigates the changes of electron transport properties in AlxGa1-xN/GaN with an inserted AlN layer. The polarization charge density and two-dimensional electron gas (2DEG) sheet density in AlxGa1-xN/AlN/GaN double heterojunction high electron mobility transistors (HEMT) affected by the spontaneous polarization and piezoelectric polarization in AlxGa1-xN and AlN barrier are studied. Relations of interface roughness scattering and alloy disorder scattering with the AlN thickness are systematically analyzed. It is found that the alloy disorder scattering is the main scattering mechanism in AlxGa1-xN/GaN heterojunction high-electron-mobility transistors, while the interface roughness scattering is the main scattering mechanism in AlxGa1-xN/AlN/GaN double-heterojunction structure. It is also known that the 2DEG sheet density, interface roughness scattering and alloy disorder scattering are depended on the thickness of the inserted AlN layer. The 2DEG sheet density increases slightly and the mobility increases obviously by inserting an AlN layer about 13 nm. Taking Al mole fraction of 0.3 as an example, if without AlN layer, the 2DEG sheet density is 1.47 1013 cm-2 with the mobility limited by the interface roughness scattering of 1.15 104 cm2V-1-1, and the mobility limited by alloy disorder scattering of 6.07 102cm2V-1-1. After inserting an AlN layer of 1 nm, the 2DEG sheet density increases to 1.66 1013cm-2, and the mobility limited by the interface roughness scattering reduces to 7.88 103cm2V-1-1 while the mobility limited by alloy disorder scattering increases greatly up to 1.42 108 cm2V-1-1.

AlGaN/GaN/InGaN/GaN DH-HEMTs with GaN channel layer grown at high temperature

The AlGaN/GaN/InGaN/GaN double heterojunction high electron mobility transistors (DH-HEMTs) sample has been grown by MOCVD on (0 0 0 1) sapphire substrate. The structure features a 7 nm In 0.046 Ga 0.954 N interlayer determined by Rutherford backscattering (RBS). Since the polarization field in the InGaN interlayer is opposite to it in the AlGaN layer, an additional potential barrier is introduced between the two-dimensional electron gas (2DEG) channel and buffer, leading to enhanced carrier confinement and improved buffer isolation. The GaN layers between the AlGaN layer and InGaN interlayer are divided into two layers consisting of GaN channel layer which provides high mobility 2DEG grown at 1070 °C and GaN spacer layer grown at the same temperature as InGaN interlayer (800 °C) to prevent indium diffusion. RBS measurement confirms that the 3 nm GaN spacer layer isolates the InGaN interlayer well and free from diffusion. Hall measurement has been performed, the mobility as high as 1552 cm 2 /V s at room temperature is obtained and the sheet carrier density is 1.55 × 10 13 cm −2 . The average sheet resistance is 331 Ω/sq, respectively. The mobility obtained in this paper is about 20% higher than similar structures reported.

Dielectric and barrier thickness fluctuation scattering in Al2O3/AlGaN/GaN double heterojunction high-electron mobility transistors

The two-dimensional electron gas (2DEG) mobility limited by dielectric and barrier thickness fluctuations (TF) scattering in Al2O3/AlGaN/GaN double heterojunction high-electron mobility transistors (HEMTs) is calculated. Calculation shows that thickness fluctuation scattering is the main limitation in Al2O3/AlGaN/GaN double heterojunction HEMTs with thin Al2O3 layer thicknesses. In addition, a study of 2DEG mobility as a function of 2DEG density, ns, shows that TF scattering acts as the main limitation when ns exceeds 2×1012cm−2. The results may be used to design HEMTs to obtain higher 2DEG mobilities by modulating the dielectric layer and barrier thicknesses or 2DEG density.

Effect of GaN Cap Layer on the Electrical Properties of AlGaN/GaN HEMT

The electrical properties of AlGaN/GaN heterojunction high electron mobility transistor (HEMT) are simulated by using sentaurus software. This paper compares two structures, the HEMT with GaN cap layer and the HEMT without GaN cap layer. The sentaurus software simulates the DC and AC characteristics of the two AlGaN/GaN HEMT structures. The HEMT with GaN cap layer can increase the maximum transconductance gm from 177ms/mm to 399ms/mm when the doping concentration of the cap layer is 3×1018cm-3 compared with the other structure under the same conditions. The simulation results indicate that the HEMT with cap layer can increase maximum transconductance gm, saturation current Ids, current-gain cutoff frequency fT, maximum oscillation frequency fmax and reduce the series resistance of the drain to source compared with the HEMT without GaN cap layer. The large Ids of the HEMT with cap layer is attributed to the increase of the concentration of two dimensional electron gas (2DEG). Moreover, the change of the doping concentration of the cap layer will affect the gm and Ids.

Theoretical calculation of the interfacial charge-modulated two-dimensional electron gas mobility in Al2O3/AlGaN/GaN double heterojunction high-electron mobility transistors

Influences of the dielectric layer-induced interfacial charges on two-dimensional electron gases (2DEGs) are theoretical calculated in thin-barrier Al2O3/AlGaN/GaN double heterojunction high-electron mobility transistors (HEMTs). A decrease of 2DEG mobilities limited by three main scattering mechanisms, including misfit dislocation, threading dislocation and interface roughness scatterings, is observed with increasing value of the density of interfacial charges. The results in this article can be used to design structures to generate higher mobility in Al2O3/AlGaN/GaN double heterojunction HEMTs.

Polarization-induced remote interfacial charge scattering in Al2O3/AlGaN/GaN double heterojunction high electron mobility transistors

This study investigated on polarization-induced remote interfacial charge scattering, a scattering mechanism caused by the interfacial polarization charge, for Al2O3/AlGaN/GaN double heterojunction high electron mobility transistors (HEMTs). Results show that remote interfacial charge scattering plays a critical role in the mobility of two-dimensional electron gas (2DEG) in thin barrier HEMTs. The electronic mobility limited by remote charge scattering is found to be a function of the fixed charge density induced by the Al2O3 layer, 2DEG density, and barrier thickness. Results of this study can be used in designing structures to generate higher electron mobility in Al2O3/AlGaN/GaN double heterojunction HEMTs.

Characteristics of AlGaN/GaN/AlGaN double heterojunction HEMTs with an improved breakdown voltage

We studied the performance of AlGaN/GaN double heterojunction high electron mobility transistors (DH-HEMTs) with an AlGaN buffer layer, which leads to a higher potential barrier at the backside of the two-dimensional electron gas channel and better carrier confinement. This, remarkably, reduces the drain leakage current and improves the device breakdown voltage. The breakdown voltage of AlGaN/GaN double heterojunction HEMTs (∼100 V) was significantly improved compared to that of conventional AlGaN/GaN HEMTs (∼50 V) for the device with gate dimensions of 0.5 × 100 μm and a gate—drain distance of 1 μm. The DH-HEMTs also demonstrated a maximum output power of 7.78 W/mm, a maximum power-added efficiency of 62.3% and a linear gain of 23 dB at the drain supply voltage of 35 V at 4 GHz.