“Ohmic-before-passivation” process was implemented on ultrathin-barrier AlGaN（<6 nm）/GaN heterostructure to further reduce the ohmic contact resistance（Rc）. In this process, alloyed Ti/Al/Ni/Au ohmic metal wa...
详细信息
“Ohmic-before-passivation” process was implemented on ultrathin-barrier AlGaN（<6 nm）/GaN heterostructure to further reduce the ohmic contact resistance（Rc）. In this process, alloyed Ti/Al/Ni/Au ohmic metal was formed first, followed by AlN/SiNxpassivation contributed to restore two-dimensional electron gas（2DEG） in the access region. Due to the sharp change in the concentration of 2DEG at the metal edge, a reduced transfer length consisted with lower Rcare achieved compared to that of ohmic contact on AlGaN（～20 nm）/GaN heterostructure with pre-ohmic recess process. Temperature-dependent current voltage measurements demonstrate that the carrier transport mechanism is dominated by thermionic field emission above 200 K and by field emission below 200 K. The “ohmic-before-passivation” process enables the relative stability of ohmic contacts between 50 K and 475 K and significantly improves the direct current characteristics of GaN-metal-insulator-semiconductor-high electron mobility transistor, offering a promising means for scaling down and enabling the utilization of low-voltage GaN-based power devices in extreme environmental conditions.
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