High performance GaN pin rectifiers grown on free-standing GaN substrates

Gallium nitride pin rectifiers grown on bulk GaN substrate have been fabricated and characterised. The device structures were grown by metal organic chemical vapour deposition (MOCVD) on free-standing GaN substrates. The diode structure consisted of an n⁺-GaN layer, followed by a 2.5 mum unintentionally doped i-GaN layer, and a p-type GaN layer capped with a p⁺⁺-GaN cap layer. The mesa-structure pin diodes exhibited a blocking voltage as large as V_r~-540 V, and a reverse current density of I_r~0.1 A/cm² at V_r~-500 V. The forward voltage drop is only 4.4 V at a forward current density of ~100A/cm², with an on-resistance of 3 mOmega middot cm² for a circular device with an 80 mum mesa diameter. The breakdown voltage and on-resistance are believed to be the best values reported for vertical mesa GaN pin rectifiers grown on bulk GaN substrates with comparable i-layer thickness