Abstract
High power electronics using wide bandgap materials are maturing rapidly, and significant market growth is expected in a near future. Ultra wide bandgap materials, which have an even larger bandgap than GaN (3.4 eV), represent an attractive choice of materials to further push the performance limits of power devices. In this work, we report on the fabrication of AlN/AlGaN/AlN high-electron mobility transistors (HEMTs) using 50% Al-content on the AlGaN channel, which has a much wider bandgap than the commonly used GaN channel. The structure was grown by metalorganic chemical vapor deposition (MOCVD) on AlN/sapphire templates. A buffer breakdown field as high as 5.5 MV/cm was reported for short contact distances. Furthermore, transistors have been successfully fabricated on this heterostructure, with low leakage current and low on-resistance. A remarkable three-terminal breakdown voltage above 4 kV with an off-state leakage current below 1 μA/mm was achieved. A regrown ohmic contact was used to reduce the source/drain ohmic contact resistance, yielding a drain current density of about 0.1 A/mm.
Highlights
Wide band gap (WBG) semiconductors such as GaN and SiC are becoming the material of choice for high power applications
An almost linear lateral buffer breakdown voltage (BV) scaling was observed on isolated ohmic contacts for various contact distances reaching values above 5 kV
AlN/AlGaN/AlN heterostructure with 50% Al content in the channel. This resulted in an increase in the critical electric field with respect to more standard GaN high-electron mobility transistors (HEMTs)
Summary
Wide band gap (WBG) semiconductors such as GaN and SiC are becoming the material of choice for high power applications. Employing AlN as a buffer layer enables it to handle extremely high voltages due to its large electric breakdown field [20,21]. The AlN buffer can potentially increase the electron confinement in the transistor channel but can help boosting the breakdown voltage (BV), owing to its wider bandgap. In this frame, the implementation of high Al content (>40%) AlGaN channel instead of GaN should allow for extremely high voltage transistor operations due to an increased critical electric field [24,25,26]
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