A bimodal deposition scheme combining radiofrequency magnetron sputtering and plasma enhanced chemical vapour deposition (PECVD) is proposed as a means for improving the performance of GaN-based metal–oxide–semiconductor high-electron-mobility transistors (MOSHEMTs). High-density sputtered-SiO2 is utilized to reduce the gate leakage current and enhance the breakdown voltage while low-density PECVD-SiO2 is employed to buffer the sputtering damage and further increase the drain current by engineering the stress-induced-polarization. Thus-fabricated MOSHEMT exhibited a low leakage current of 4.21 × 10−9 A mm−1 and high breakdown voltage of 634 V for a gate–drain distance of 6 µm, demonstrating the promise of bimodal-SiO2 deposition scheme for the development of GaN-based MOSHEMTs for high-power application.
Selective-area growth (SAG) based on plasma-assisted molecular-beam epitaxy (PAMBE) was shown to facilitate improvement of Ohmic contacts and directcurrent (DC) characteristics for GaN-based field-effect transistors (FETs) over the widely accepted ion-implantation technique. Twofold improvements in breakdown voltage were also demonstrated for samples grown on both sapphire and silicon substrates. An AlGaN/GaN high-electron-mobility transistor (HEMT) fabricated with PAMBE-SAG exhibited a low specific contact resistivity of 5.86 9 10 À7 X cm 2 , peak drain current of 420 mA/mm, and high breakdown voltage of 77 V. These results demonstrate that PAMBE-SAG is suited to fabricating HEMTs for high-power applications.
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