Tingang Liu

High-temperature Ohmic contact annealing is universally required in aluminum nitride (AlN) power device fabrication, yet its impact on adjacent AlN surfaces subsequently used for Schottky contact formation has never been investigated. We show that the Ohmic metal stack in combination with 950 °C rapid thermal processing markedly roughens the adjacent AlN surface, increasing the root mean square roughness from below 0.5 nm to approximately 2 nm and rendering AlN Schottky barrier diodes non-rectifying. This degradation is absent when the same thermal budget is applied without the metal stack, identifying that the thermal budget alone is not the causal factor. Cross-sectional scanning transmission electron microscopy and energy-dispersive x-ray spectroscopy reveal AlOx- and Al-N-O-related interfacial layers formed at the Schottky contact region as a direct consequence of this annealing process. Sequential pretreatment by buffered oxide etching and atomic layer etching removes these layers, reduces the surface roughness to 0.3 nm, and recovers near-ideal Schottky characteristics with an ideality factor of 1.36. Temperature-dependent reverse current–voltage and multifrequency conductance analyses identify trap-assisted tunneling as the dominant reverse leakage mechanism. These findings uncover a previously unrecognized process-coupling effect between high-temperature Ohmic contact annealing and subsequent Schottky interface formation in AlN power device fabrication and provide a practical surface recovery route toward reliable rectifying contacts.

In this work, enhancement-mode p-MOSFETs on p-GaN/AlGaN/GaN-on-Si substrates were fabricated using a gate recess process that combines reactive ion etching (RIE) with atomic layer etching (ALE), where ALE is employed as an interface engineering approach following conventional plasma etching to mitigate recess-induced interface damage. Compared with RIE-only devices, the RIE + ALE devices yield smoother surfaces and significantly suppress interface trap density. These interface improvements lead to enhanced subthreshold characteristics and markedly tighter device-to-device uniformity. In particular, the subthreshold swing decreased from 365 ± 179 to 149 ± 17 mV/dec, while the off-state leakage current was suppressed from 1.9 ± 3.6 × 10−7 to 8.5 ± 5.5 × 10−9 mA/mm. These results demonstrate that ALE provides an effective interface engineering approach for suppressing interface damage and enabling uniform enhancement-mode p-MOSFETs, highlighting its potential for reliable GaN complementary metal–oxide–semiconductor logic and power integrated circuits.

P-GaN diodes exhibit large reverse currents due to poor Schottky contacts between p-GaN and metal, which hinders their application in environmentally robust power systems and GaN complementary metal–oxide–semiconductor (CMOS) integration. In this study, we have proposed a p-GaN diode structure incorporating a Si-rich amorphous SiOx interlayer that effectively suppresses the reverse current from 2.58 × 10−4 to 1.48 × 10−6 A at 10 V, a reduction of more than two orders of magnitude. Meanwhile, the forward current remains high, decreasing only slightly from 5.73 × 10−4 to 5.24 × 10−4 A at −10 V, thus maintaining high on-state current capability. X-ray photoelectron spectroscopy (XPS) reveals the oxygen-deficient nature of the SiOx layer. Temperature-dependent I–V measurements demonstrate that this layer effectively suppresses Fowler–Nordheim tunneling and thermionic field emission, which are typically responsible for the high leakage current in heavily doped p-GaN diodes. This suppression shifts the dominant conduction to variable-range hopping, leading to a significant reduction in reverse current. These findings underscore the potential of the proposed structure to achieve high-performance p-GaN devices, paving the way for next-generation GaN CMOS circuits.

Surface defects in Al-rich AlGaN Schottky barrier diodes (SBDs) contribute to high reverse leakage currents, which limit breakdown voltage—a critical parameter for power applications. In this study, atomic layer etching (ALE) was applied to the Schottky contact area to remove surface defects and native oxide. SBDs without ALE treatment exhibited a breakdown voltage of 308 V, whereas ALE-treated devices achieved a significantly improved breakdown voltage of 1205 V. By reducing interface traps and eliminating native oxide, ALE leads to lower leakage current and a more uniform Schottky barrier. These findings demonstrate that ALE is an effective surface treatment for enhancing the interface quality of III-nitride Schottky barrier diodes, paving the way for high-performance devices and promising advances in other nitride-based power electronics.

In this letter, we present a high-performance aluminum nitride (AlN) lateral Schottky barrier diode (SBD) achieved through rapid thermal annealing (RTA) in an oxygen environment. This treatment dramatically reduces the reverse leakage current and significantly enhances the Schottky contact performance. These treated SBDs exhibit impressive room temperature (RT) characteristics, including a rectification ratio of ~10⁷, an ideality factor of 2.04, a barrier height of 1.84 eV, and the highest breakdown voltages at the kilovolt level. Even under elevated temperatures, these devices maintain exceptional stability, showcasing their robust performance. This notable enhancement results from effective defect compensation, reducing defect-assisted tunneling paths. X-ray photoelectron spectroscopy (XPS) and capacitance–voltage analysis confirm the presence of an oxygen diffusion layer near the AlN surface posttreatment, further contributing to enhanced defect compensation. This work marks a significant milestone in advancing AlN SBDs, offering the potential for more efficient and reliable devices in high-power applications.

The size of InGaN micro-LEDs is continuously decreasing to meet the demands of various emerging applications, especially in tiny micro-displays such as AR/VR. However, the conventional pixel definition based on plasma etching significantly damages the mesa sidewalls, leading to a severe reduction in efficiency as the micro-LED size decreases. This seriously impedes the development and application of micro-LEDs. In this work, we comprehensively explain the origin of micro-LED sidewall effects and corresponding physical models. Subsequently, we systematically review recent progress in micro-LED fabrication aiming at suppressing sidewall effects. Furthermore, we discuss advancements in micro-LED fabrication with “damage-free” techniques, which hold the potential to fundamentally address the issue of plasma damage in the micro-LED process. We believe this review will deepen the understanding of micro-LED sidewall effects and provide a better insight into the latest associated fabrication technologies for high-efficient InGaN micro-LEDs.

High-quality aluminum nitride (AlN) films on silicon substrates are crucial for various applications due to their inherent properties as wide-bandgap semiconductors, cost-effectiveness, and compatibility with silicon-based circuits. Nonetheless, producing high-quality and crack-free AlN on silicon presents significant challenges due to the stress caused by lattice and thermal expansion mismatches. This study introduces a method to mitigate these challenges by incorporating a boron precursor during the metalorganic chemical vapor deposition process to form a BAlN buffer layer. Analytical techniques, such as secondary ion mass spectrometry, atomic force microscopy imaging, XRD rocking curves, reciprocal space map, and Raman spectroscopy, indicate that the BAlN buffer layer promotes the enlargement of seed crystal size, which effectively delays AlN coalescence, mitigates accumulated tensile stress, and enhances the overall crystal quality. Employing this technique has produced a 520 nm thick, crack-free AlN film on silicon (111) with high crystal quality, achieving full width at half maximum values of only 0.2° and 0.3° for XRC (002) and (102), respectively.

Ultrawide bandgap aluminum nitride (AlN) stands out as a highly attractive material for high-power electronics. However, AlN power devices face performance challenges due to high contact resistivity exceeding 10−1 Ω cm2. In this Letter, we demonstrate achieving a low contact resistivity at the 10−4 Ω cm2 level via refined metallization processes applied directly to n-AlN. The minimum contact resistivity reached 5.82 × 10−4 Ω cm2. Our analysis reveals that the low contact resistance primarily results from the stable TiAlTi/AlN interface, resilient even under rigorous annealing conditions, which beneficially forms a thin Al–Ti–N interlayer, promotes substantial nitrogen vacancies, enhances the net carrier density at the interface, and lowers the contact barrier. This work marks a significant milestone in realizing superior Ohmic contacts for n-type AlN, paving the way for more efficient power electronic and optoelectronic devices.

This study investigated the growth of AlN epitaxial films on 2-in. Si(111) via metal-organic chemical vapor deposition. By introducing triethylboron (TEB) during trimethylaluminum pretreatment, a nearly crack free AlN epilayer with a thickness of 500 nm was acquired. The x-ray diffraction rocking curves of AlN (002) and (102) exhibited full width at half maximum values of 0.22° and 0.36°, respectively. Atomic force microscopy image analysis showed that after the introduction of TEB, larger grains appeared on the surface of Si(111) substrate, promoting the 3D growth pattern of the subsequent AlN buffer layer. Laytec reflection curves depicted the morphological transition from 3D to 2D growth mode during AlN deposition. At the same time, the curvature value was significantly reduced by 20 km−1, and the Raman spectrum peak of E2(high) shifted from 648.7 to 652.5 cm−1, indicating that the surface tensile stress was greatly reduced, effectively suppressing the crack problem of AlN on Si(111).