GaN Micropillar Schottky Diodes with High Breakdown Voltage Fabricated by Selective-Area Growth

Abstract

Herein, selective-area growth (SAG) of lightly n-doped GaN micropillars on masked GaN-on-sapphire templates is investigated. Using the micropillar SAG approach, the maximum GaN drift layer thickness in Schottky diodes on foreign substrates is increased. Thus, cost-efficient vertical power devices with large breakdown voltages (VBD) based on heteroepitaxy are enabled. The influence of different hard-mask materials and SAG temperatures (TSAG) on growth selectivity, morphology, and net doping concentration (ND–NA) is investigated. By using an AlOx hard mask and TSAG = 1045 °C, 3.7 μm high GaN micropillars are grown in circular mask openings. Quasi-vertical Schottky diodes on these pillars exhibit low ND–NA = 5.2 × 1016 cm−3, VBD = 393 V, and a critical electric field EC = 2.63 MV cm−1.