Research progress of aluminum nitride materials and devices

The ultra-wide bandgap semiconductor represented by aluminum nitride is the fourth generation of semiconductor materials after silicon, gallium arsenide, gallium nitride and silicon carbide, which has been recognized as the key technology to promote the rapid development of microelectronics technology and become the commanding point of technology competition in the world. With high power, high voltage, high temperature and radiation resistance, ultra-wide bandgap semiconductor is the ideal material for the new generation of high-power integrated circuits, power electronic power devices, short-wavelength photoelectric devices and detector parts.

Aluminum nitride material

Aluminum nitride (AlN) is a typical Ⅲ-V compound with excellent physical and chemical properties, such as high thermal stability (melting point 2100 ℃), high thermal conductivity [2W/(cm·K)], and high chemical stability. AIN also has good piezoelectric and dielectric properties, so it has great application value in energy conversion, acoustic wave and MEMS devices, and has been used in MEMS. The research on AlN materials mainly focuses on two aspects: AlN crystal growth and AlN film epitaxy. Among them, the growth of AlN crystal mainly adopts PVT method to grow autoseed crystal and heteroseed crystal. AlN film epitaxy is mainly grown on sapphire or 4H-SiC substrate by MOCVD, ALD and other methods.

Aluminum nitride device

The research of AlN devices mainly focuses on diodes, MESFETs, photodetectors, etc. Among them, ALN-based diodes show better characteristics and have been widely studied. In 2023, Arizona State University achieved the first AlN Schottky diode on an AlN substrate with a breakdown voltage of 3 kV and a leakage current of only 200 nA. In 2024, Nagoya University used distributed polarization doping method to prepare AlGaN p-n vertical diode on AlN substrate, as shown in Figure 8 (a). The breakdown field strength reached 7.3MV /cm, and the opening voltage of 6.5V and the on-resistance of 3mΩ ·cm2 were realized. It is the minimum value of ALN-based p-n diode reported so far. In the same year, XIdian University implemented a high-performance AlN/GaN double barrier resonant tunneling diode with a record peak current of 1551 kA/cm2 and a peak-to-valley current ratio of 1.24.

In addition, due to the high polarization effect of AlN, the channel electron surface density in the AlN/GaN heterojunction is extremely high, which is suitable for making RF devices, and its high ohmic contact resistance is usually solved by quadratic epitaxy. In 2022, Xidian University proposed a low-damage enhanced AlN/GaN HEMT for remote plasma oxidation treatment, with a threshold voltage of 0.4V and a maximum current of 1.06A /mm. In 2023, Peking University reported AlN/GaN HEMT with 70 nm gate length, ohmic contact resistance as low as 0.09 Ω·mm, fT/fmax up to 140/301 GHz, and saturation current density up to 1.54 A/mm.

In the Status of the Power Electronics Industry Report, Yole Intelligence predicts that by 2028, the global power device market will increase to 33.3 billion US dollars, promoting the rapid development of the wide band gap semiconductor field. However, the existing GaN and SiC systems are difficult to meet the growing military and civilian technical requirements. As an ultra-wide band-gap semiconductor, Ga2O3 can achieve accurate modulation of N-type electronic structure, diamond has the highest thermal conductivity at room temperature, and AlN has an extremely wide band gap and better polarization characteristics. These excellent characteristics make it have broad application prospects in the fields of high voltage, high frequency, high temperature and high power electronic devices, and it is possible to realize low-cost and small volume products while higher power, frequency and efficiency.

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