Al-rich AlxGa1−xN (x ≥ 0.8) is promising for power and deep-ultraviolet (DUV) optoelectronic applications, owing to its ultra-wide bandgap and excellent thermal stability. However, forming low-resistivity contacts on n-type Al-rich AlGaN remains a significant challenge. In this work, we utilized an Au-free Ti/Al/Ti metal stack contact on n-type Al-rich AlGaN without graded layers. Record-low contact resistivities were achieved after annealing: 1.52×10−6 Ω·cm2 for n-Al0.8Ga0.2N, 3.56×10−6 Ω·cm2 for n-Al0.86Ga0.14N, and 5.79×10−5 Ω·cm2 for n-Al0.9Ga0.1N. These results demonstrate a significant advancement in forming low-resistance contacts directly on Al-rich n-AlGaN, offering a viable path forward for next-generation power electronics and DUV optoelectronic devices.
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This work demonstrates a high-performance vertical GaN p-i-n diode based on a buried p-layer n-p-i-n epitaxial structure. The post-etch magnesium (Mg) diffusion process is applied to suppress the etch-induced surface damage on the p-GaN layer. The Mg diffusion effectively reduces the valence band barrier from 2 eV to 1.1 eV, yielding a low specific contact resistivity of 6.521 × 10−4 Ω·cm2. As a result, the fabricated devices exhibit markedly enhanced forward characteristics, including a reduced turn-on voltage of 3.3 V and a specific on-resistance of 0.92 mΩ·cm2. Temperature-dependent forward I-V measurements indicate that the dominant carrier transport mechanism evolves from defect-related tunneling in the etched devices toward transport dominated by intrinsic p–n junction conduction after Mg diffusion. In addition, the devices exhibit excellent stability in forward conduction, with a voltage variation of approximately 0.028 V. These results indicate that Mg diffusion effectively improves the contact characteristics degraded by ICP etching and provide a viable approach for achieving high-performance and reliable vertical GaN power devices.
In this paper, a compact and low-power sub-THz direct-conversion receiver with a second-harmonic-remixed LO chain is proposed. Based on a common-mode second-harmonic-enhanced network, the common-mode second-harmonic voltage at the drains of the common-source differential pair in the tripler is enhanced and mixed with the fundamental voltage at the gate to generate additional differential third-harmonic voltage. Hence, the saturation output power and efficiency of the triplers used in the LO chain have been significantly improved. The power consumption of the LO chain employed in the receiver is as low as 65 mW. Measurement results demonstrate that the receiver achieves a conversion gain of 30.5 dB and a 3-dB RF bandwidth of 34 GHz, while the in-band minimum noise figure is 9.9 dB.
