GaN-based MOSFETs Research Articles

Comparison of the performance of Si, SiC, and GaN based switching elements in high gain DC-DC boost converter

Abstract In this study, Si, SiC, and GaN based semiconductor switching elements to be used in the design of new generation high gain DC-DC converters are compared. Each switching element is tested at different frequencies and different pulse period ratios. The efficiency and output voltage of the high gain boost converter are analyzed in detail according to the switching element used. The amplifiers have been investigated at 50 kHz and 5 MHz switching frequencies. The results show that the converter using GaN-based MOSFET is more efficient than converters using other MOSFETs and reaches the highest efficiency at 200 kHz switching frequency. The proposed converter achieves 91.68% efficiency and 2.66 voltage gain at 0.3 pulse period rate, 94% efficiency and 3.78 voltage gain at 0.5 pulse period rate and 93.94% efficiency, and 6.33 voltage gain at 0.7 pulse period rate. Thus, it is understood that when GaN based MOSFETs are used in high gain DC-DC converters, higher gain and higher efficiency are achieved.

Small Signal Parameters Extraction and RF Performance of GaN-Based Dual-Metal Cylindrical Surrounding Gate Junctionless Accumulation-Mode (DM-CSG-JAM) MOSFET

In this paper, small-signal model parameters and RF characteristics of the GaN-based Dual-Metal Cylindrical Surrounding Gate-Junctionless Accumulation Mode (DM-CSG-JAM) MOSFET has been extracted. Better scattering parameters has been observed for GaN-based DM-CSG-JAM MOSFET over other analogous structures which confirms its applications for RF domain. Also, enhanced drain current, transconductance, cut-off frequency, I on/I off ratio, etc. have been observed for the GaN-based device. The performance of the GaN-based MOSFET has also been compared with the other compound semiconductors (GaAs, InP) and silicon-based DM-CSG-JAM MOSFET. On account of the eminent properties possessed by GaN, the GaN-based device shows outstanding characteristics over the other semiconductor-based device.

Atomic structure and band alignment at Al2O3/GaN, Sc2O3/GaN and La2O3/GaN interfaces: A first-principles study

The atomic structures, chemical bonding and band alignment at trivalent oxides X2O3 (where X = Al, Sc and La) and GaN interface are studied based on the density functional supercell calculations. The insulating interfaces with small roughness and a clean bandgap are built based on the electron counting rule. The results prove that GaO bonds dominate the interfacial chemical bonding for all the interfaces, and the calculated oxide/GaN band alignment consistent with the experimental values. All the oxides are proved to have the type-I band alignment with GaN with hybrid functional calculation. For the Al2O3 interface, the calculated valence band offset is 1.17 eV, while that for the Sc2O3 and La2O3 interface are 0.81 eV and 0.95 eV, respectively. The calculated conduction band offsets are all larger than 1 eV, and as large as 1.8 eV for the Al2O3 interface. The theoretically calculated band alignments indicate that the studied trivalent oxides Al2O3, Sc2O3 and La2O3 are all suitable gate insulators for GaN-based MOSFET applications.

Chemical bonding and band alignment at X2O3/GaN (X = Al, Sc) interfaces

The chemical bonding and the band alignment at Al2O3/GaN and Sc2O3/GaN interfaces are studied using density functional supercell calculations. Using bonding models based on the electron counting rule, we have created the insulating interfaces with a small roughness and a clean bandgap. Ga-O bonds dominate the interfacial chemical bonding at both interfaces. The calculated band alignment agrees with the experimental values. For the Al2O3 interface, the calculated valence band offset is 1.17 eV using hybrid functionals, while that for the Sc2O3 interface is 0.81 eV. The conduction band offsets for both are larger than 1 eV, and is as large as ∼2 eV for the Al2O3 interface. The calculated band alignments indicate that Al2O3 and Sc2O3 are both suitable insulators for GaN-based MOSFET applications.

Electrical Comparison of ${\rm HfO}_{2}$ and ${\rm ZrO}_{2}$ Gate Dielectrics on GaN

A low-temperature atomic layer deposition technique for high-κ dielectric films on GaN templates was investigated for MOS applications. This improved growth method produced capacitance densities and a field effect mobility approaching 375 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs for ZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and 250 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> /Vs for HfO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> films on GaN. Furthermore, the low density of dielectric-semiconductor interface traps confirmed a reliable cohesion between the high-κ and GaN. The improved gate dielectric deposition technique has the capabilities to improve the overall quality of GaN-based MOSFETs.

Normally Off GaN Power MOSFET Grown on Sapphire Substrate With Highly Resistive Undoped Buffer Layer

A high-performance normally off GaN-based MOSFET was fabricated. The buffer layer of the MOSFET was grown by varying the growth temperature to control the size of nucleation sites which results in an extremely high buffer resistance <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(&gt; \hbox{10}^{12}\ \Omega/\hbox{sq})$</tex></formula> . The fabricated small-area MOSFET exhibited excellent normally off device characteristics, such as a threshold voltage of 2 V, maximum drain current of 253 mA/mm, on–off current ratio of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$ \hbox{5.5} \times \hbox{10}^{7}$</tex></formula> , destructive breakdown voltage of 830 V, and leakage current of 0.7 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{A/mm}$</tex></formula> at a <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$V_{\rm DS}$</tex></formula> of 600 V. The corresponding values of the large-area MOSFET with a multifinger pattern were 0.6 V, 6 A, <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hbox{1.3} \times \hbox{10}^{7}$</tex></formula> , 670 V, and 50 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{A}$</tex></formula> (0.28 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu \hbox{A/mm}$</tex></formula> ).

(Invited) High Power Normally-Off GaN MOSFET

The enhancement mode n-channel GaN-based MOSFETs on Si substrates have been demonstrated. We achieved a low interface state density between SiO2 and GaN, a high breakdown field, and a high reliability of SiO2 by annealing after SiO2 deposition on GaN. The SiO2 was applied for the gate oxide of GaN MOSFET. The fabricated GaN MOSFETs using an ion implantation technique showed good normally-off operation with threshold voltage of 2.7 V, the maximum output current of over 3.5 A, and a high-temperature operation up to 300oC. Furthermore, AlGaN/GaN hybrid MOS-HFETs were fabricated. The MOS-HFET has the merits of both a MOS channel and an AlGaN/GaN heterostructure with high mobility two dimensional electron gases. The maximum drain current of over 100 A was performed. The specific on-state resistance was 9.3 mΩ-cm2. The fabricated device also exhibited good normally-off operation and the breakdown voltage of over 600 V.