Performance enhancement of GaN SB-MOSFET on Si substrate using two-step growth method

We have grown high quality GaN layers on (1 1 1)-oriented silicon substrate using a two-step growth method and fabricated high-performance normally-off n-channel GaN Schottky-barrier MOSFET (SB-MOSFET). Indium-tin-oxide (ITO) was used as Schottky-barrier contact for source and drain (S/D) because the work function of ITO is close to the electron affinity of GaN. Due to enhanced crystalline quality and reduced surface roughness of GaN layer grown by two-step process, the fabricated device exhibited much improved performances: sufficiently high threshold voltage of 3.75 V, subthreshold slope of 171 mV/dec, low specific on-resistance of 9.98 mΩ cm2, and very high field-effect mobility of 271 cm2/V s. This is the highest mobility value among the GaN MOSFETs ever reported so far.

We grow high quality GaN layer on Si substrate using two-step growth method. The crystal quality and surface roughness of GaN are enhanced by 1st GaN layer. 1st GaN layer grown under high pressure with high V/III ratio results in three dimensional islands which are effective in blocking dislocation propagation and promoting coalescence of 2nd GaN layer. SB-MOSFET fabricated on GaN layer exhibits much improved performances, such as saturation drain current of 54 mA/mm, subthreshold slope of 171 mV/dec, and low specific on-resistance 9.98 mΩ cm2. The extracted electron mobility is 271 cm2/V s which sands as a record value.Figure optionsDownload as PowerPoint slide