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

Abstract

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 µm 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 Vr∼−540 V, and a reverse current density of Ir∼0.1 A/cm2 at Vr∼−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 mΩ · cm2 for a circular device with an 80 µm 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.