posted on 2024-01-24, 20:34authored byXiaoyu Zhao, Ke Sun, Zhenxing Lv, Zhefu Liao, Sheng Liu, Shengjun Zhou
Throughout
the development of III-nitride electronic and optoelectronic
devices, electrically interfacing III-nitride semiconductors and metal
schemes has been a long-standing issue that determines the contact
resistance and operation voltage, which are tightly associated with
the device performance and stability. Compared to the main research
focus of the crystal quality of III-nitride semiconductors, the equally
important contact interface between III-nitrides and metal schemes
has received relatively less attention. Here, we demonstrate a comprehensive
contact engineering strategy to realize low resistance to Al-rich
n-AlGaN via pretreatment and metal scheme optimization. Prior to the
metal deposition, the introduction of CHF3 treatment is
conducive to the substantial resistance reduction, with the effect
becoming more distinct by prolonging the treatment time. Furthermore,
we compare different metal schemes, namely, Ti/Al/Ti/Au, Ti/Al/Ti/Pt/Au,
and Cr/Ti/Al/Ti/Pt/Au, to form electrical contact on n-AlGaN. From
microscale analysis based on multiple characterization methods, we
reveal the correlation between electrical properties and the nature
of the contact interface, attributing the contact improvement to the
low-resistance Pt- and Cr-related alloy formation. Under the circumstance
that no efforts have been devoted to optimizing the epitaxial growth,
engineering the metal–semiconductor contact properties alone
leads to a resistance value of 8.96 × 10–5 Ω·cm2. As a result, the fabricated deep-ultraviolet LEDs exhibit
an ultralow forward voltage of 5.47 V at 30 A/cm2 and a
33% increase in the peak wall-plug efficiency.