In this paper, we present a comprehensive reviewand discussion of the state-of-the-art device technology and application development of GaN-on-Si power electronics. Several device technologies for realizing normally off operation that is highly desirable for power switching applications are presented. In addition, the examples of circuit applications that can greatly benefit from the superior performance of GaN power devices are demonstrated. Comparisonwith other competingpower device technology, such as Si superjunction-MOSFET and SiC MOSFET, is also presented and analyzed. Critical issues for commercialization of GaN-on-Si power devices are discussed with regard to cost, reliability, and ease of use.

GaN-on-Si Power Technology: Devices and Applications

An object is to provide a method for manufacturing a semiconductor device, in which the number of photolithography steps can be reduced, the manufacturing process can be simplified, and manufacturing can be performed with high yield at low cost A method for manufacturing a semiconductor device includes the following steps: forming a semiconductor film; irradiating a laser beam by passing the laser beam through a photomask including a shield for shielding the laser beam; subliming a region which has been irradiated with the laser beam through a region in which the shield is not formed in the photomask in the semiconductor film; forming an island-shaped semiconductor film in such a way that a region which is not irradiated with the laser beam is not sublimed because it is a region in which the shield is formed in the photomask; forming a first electrode which is one of a source electrode and a drain electrode and a second electrode which is the other one of the source electrode and the drain electrode; forming a gate insulating film; and forming a gate electrode over the gate insulating film

Method for Manufacturing Semiconductor Device

There is a great interest in wide-bandgap semiconductor devices and most recently in monolithic GaN structures for power electronics applications. In this paper, vertical p-n diodes fabricated on pseudobulk low defect density ( $10^{4}$ – $10^{6}$ cm $^{-2}$ ) GaN substrates are discussed. Homoepitaxial low-pressure metal organic chemical vapor deposition growth of GaN on its native substrate and being able to control and balance the n-type Si doping with background C impurity has allowed the realization of vertical device architectures with drift layer thicknesses of 6 to 40 $\mu $ m and net carrier electron concentrations of $4\times 10^{15}$ to $2.5\times 10^{16}$ cm $^{-3}$ . This parameter range is suitable for applications requiring breakdown voltages (BVs) of 600 V–4 kV with a proper edge termination strategy. Measured devices demonstrate near power device figure of merit, that is, differential specific on-resistance ( $R_{{{\textrm {sp}}}}$ ) of 2 m $\Omega $ cm $^{2}$ for a BV of 2.6 kV and 2.95 m $\Omega $ cm $^{2}$ for a 3.7-kV device, respectively. The improvement in the substrate quality over the last few years has resulted in the fabrication of diodes with areas as large as 16 mm $^{2}$ , with BVs exceeding 700 V and pulsed (100 $\mu $ s) currents of 400 A. The structures fabricated are utilized to study in detail the temperature dependency of $I$ – $V$ characteristics, impact ionization and avalanche characteristics, and extract (estimate) modeling parameters such as electron mobility in the GaN $c$ -direction (vertical) and hole minority carrier lifetimes. Some insight into device reliability is also provided.

Vertical Power p-n Diodes Based on Bulk GaN

In this paper, we report on 1.2-kV-class vertical GaN-based trench metal–oxide–semiconductor field-effect transistors (MOSFETs) on a free-standing GaN substrate with a low specific on-resistance. A redesigned epitaxial layer structure following our previous work with a regular hexagonal trench gate layout enables us to reduce the specific on-resistance to as low as 1.8 mΩcm2 while obtaining a sufficient blocking voltage for 1.2-kV-class operation. Normally-off operation with a threshold voltage of 3.5 V is also demonstrated. To the best of our knowledge, this is the first report on vertical GaN-based MOSFETs with a specific on-resistance of less than 2 mΩcm2.

http://iopscience.iop.org/article/10.7567/APEX.8.054101/pdf

1.8 mΩ·cm2 vertical GaN-based trench metal–oxide–semiconductor field-effect transistors on a free-standing GaN substrate for 1.2-kV-class operation

Many power switching devices are used in hybrid vehicles (HVs) and electric vehicles (EVs). To improve the efficiency of HVs and EVs, better performance characteristics than those of Si power devices, for example, lower on-resistance, higher speed, higher operation temperature, are required for the power devices. GaN power devices are promising candidates for satisfying the requirements. A lateral GaN power device with a blocking voltage of 600 V and a vertical GaN power device with a blocking voltage of 1200 V are suitable for medium power applications for sub systems and high-power applications for the drive of main motors, respectively. Power device applications in HVs and EVs and the current status of the GaN power device are presented. The reliability of the GaN power device is also discussed.

https://iopscience.iop.org/article/10.7567/JJAP.53.100210/pdf

Recent progress of GaN power devices for automotive applications

Completely vertical trench gate metal oxide semiconductor field-effect transistors (MOSFETs) have been produced using gallium nitride (GaN) for the first time. These MOSFETs exhibited enhancement-mode operation with a threshold voltage of 3.7 V and an on-resistance of 9.3 mΩcm2. The channel mobility was estimated to be 131 cm2/(Vs) when all the resistances except for that of the channel are considered. Such structures, which satisfy the key words "vertical", "trench gate", and "MOSFET", will enable us to fabricate practical GaN-based power switching devices.

https://iopscience.iop.org/article/10.1143/APEX.1.011105/pdf

Vertical GaN-Based Trench Gate Metal Oxide Semiconductor Field-Effect Transistors on GaN Bulk Substrates

A nitride semiconductor device includes: a semiconductor base layer made of a conductive group III nitride semiconductor having a principal plane defined by a nonpolar plane or a semipolar plane; an insulating layer formed on the principal plane of the semiconductor base layer with an aperture partially exposing the principal plane; a nitride semiconductor multilayer structure portion, formed on a region extending onto the insulating layer from the aperture, having a parallel surface parallel to the principal plane of the semiconductor base layer as well as a +c-axis side first inclined surface and a −c-axis side second inclined surface inclined with respect to the principal plane of the semiconductor base layer and including two types of group III nitride semiconductor layers at least having different lattice constants; a gate electrode formed to be opposed to the second inclined surface; a source electrode arranged to be electrically connected with the group III nitride semiconductor layers; and a drain electrode formed on a back surface of the semiconductor base layer opposite to the principal plane.

Nitride semiconductor device and method for producing nitride semiconductor device

Recessed-gate GaN metal-oxide-semiconductor field-effect transistors with a double-insulator gate configuration demonstrate 10-MHz switching operation of which delay time is <;35 ns. The recess structure is fabricated by etching the Al0.19Ga0.81N layers to expose their underlying AlN layers. The devices include a thermally oxidized AlN layer onto which an Al2O3 film is formed by atomic layer deposition, which works as a gate insulator. This structure performs enhancement-mode operation with a typical threshold voltage of 1.4 V. A maximum drain current of 158.3 mA/mm is achieved at 6 V gate bias and maximum transconductance is 52.1 mS/mm at 10 V drain bias.

Recessed-Gate Enhancement-Mode GaN MOSFETs With a Double-Insulator Gate Providing 10-MHz Switching Operation

This paper focuses on a development and an evaluation of high-speed gate drive circuit for SiC power MOSFET by GaN HEMT. The increasing requests to SiC power devices face to the difficulty of the gate drive because of the mismatching between device parameters and conventional driving circuits for Si power devices. Up to now, high frequency switching is the main target of logic and radio applications of active devices. The drive circuit of power devises has not been considered at the switching over MHz. Moreover, p-type SiC and GaN power devices are still not in our hand in spite of the development of n-type device. Therefore there are difficulties in the design of symmetric circuit structure to avoid the management of ground setting. This paper proposes a gate drive circuit applied GaN devices for high-speed switching of an SiC MOSFET. The proposed circuit is designed for the operation of SiC MOSFET at 10MHz. The feasibility is confirmed through a simple switching circuit.

/pdf/high-speed-gate-drive-circuit-for-sic-mosfet-by-gan-hemt-4xmaihb50e.pdf

High-speed gate drive circuit for SiC MOSFET by GaN HEMT

PROBLEM TO BE SOLVED: To provide the method of manufacturing a nitride semiconductor element, small in a contact resistance between a p-type layer and an electrode, and capable of increasing the carrier concentration in the p-type layer, by omitting a process for annealing wherein impurities are readily adhered and keeping crean the surface of the p-type layer. SOLUTION: An epitaxial growth layer 6 including the p-type layer 5 at least on the surface is formed by the vapor phase epitaxial growth of the nitride semiconductor layer on a substrate 1 to grow the most front surface layer 5 of the epitaxial growth layer 6. Thereafter, a protective layer 7 consisting of In x Ga 1-x N (0 COPYRIGHT: (C)2007,JPO&INPIT

Kentaro Chikamatsu

Papers

Vertical GaN-Based Trench Gate Metal Oxide Semiconductor Field-Effect Transistors on GaN Bulk Substrates

Nitride semiconductor device and method for producing nitride semiconductor device

Recessed-Gate Enhancement-Mode GaN MOSFETs With a Double-Insulator Gate Providing 10-MHz Switching Operation

High-speed gate drive circuit for SiC MOSFET by GaN HEMT

Method of manufacturing nitride semiconductor element