N-Face GaN/AlGaN HEMTs Fabricated Through Layer Transfer Technology

We present a new method to fabricate N-face GaN/AlGaN high electron mobility transistors (HEMTs). These devices are extremely promising for ultrahigh frequency applications where low contact resistances and excellent carrier confinement are needed. In this letter, the N-face of a Ga-face AlGaN/GaN epilayer grown on Si(111) is exposed by removing the Si substrate. To provide mechanical support, prior to the substrate removal, the Ga-face of the wafer is bonded to a Si(100) carrier wafer. The resultant N-face GaN/AlGaN heterostructures exhibited record transport properties ($mu_{e} !=! hbox{1670} hbox{cm}^{2}/hbox{V}cdot hbox{s}$, $n_{s} !=! hbox{1.6} !times! hbox{10}^{13}/ hbox{cm}^{2}$, and $R_{rm sh} = hbox{240} Omega/hbox{sq}$ ). These excellent transport properties rendered N-face HEMTs with 30% higher maximum drain current than Ga-face HEMTs and good RF characteristics ($f_{T} = hbox{10.7} hbox{GHz} cdot muhbox{m}$ and $f_{max} = hbox{21.5} hbox{GHz}cdot muhbox{m}$), comparable to state-of-the-art Ga-face devices.