All MOCVD grown Al0.7Ga0.3N/Al0.5Ga0.5N HFET: An approach to make ohmic contacts to Al-rich AlGaN channel transistors
2019; Elsevier BV; Volume: 164; Linguagem: Inglês
10.1016/j.sse.2019.107696
ISSN1879-2405
AutoresHao Xue, Seongmo Hwang, Towhidur Razzak, Choonghee Lee, Gabriel Calderón Ortiz, Zhanbo Xia, Shahadat H. Sohel, Jinwoo Hwang, Siddharth Rajan, Asif Khan, Wu Lu,
Tópico(s)Semiconductor materials and devices
ResumoWe report a gate recessed Al0.7Ga0.3N/Al0.5Ga0.5N heterostructure field effect transistor (HFET) with a graded contact cap layer grown by metal organic chemical vapor deposition (MOCVD) on AlN/Sapphire substrate. A low specific contact resistivity ρc of 2.1 × 10−5 Ω·cm2 is demonstrated with current injection from the top of the Al0.7Ga0.3N barrier to the Al0.5Ga0.5N channel. The device with a gate length of 160 nm exhibits a drain current density at gate shorted to source (ID,SS) of 420 mA/mm, a cutoff frequency fT of 20 GHz, and a maximum oscillation frequency (fmax) of 40 GHz. The same device has a three terminal off-state gate-to-drain breakdown voltage of 170 V, corresponding to an average breakdown field (FBR) of 2.8 MV/cm between the gate and drain, due to drain induced barrier lowering effect. Devices with a gate length of 1 µm demonstrate a gate to drain breakdown voltage of 195 V or an average breakdown field of 3.9 MV/cm. This work provides a way to make ohmic contacts to Al-rich AlGaN channel heterojunction transistors for high power and high frequency applications.
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