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

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 (V-BD) based on heteroepitaxy are enabled. The influence of different hard-mask materials and SAG temperatures (T-SAG) on growth selectivity, morphology, and net doping concentration (N-D-N-A) is investigated. By using an AlOx hard mask and T-SAG = 1045 degrees C, 3.7 mu m high GaN micropillars are grown in circular mask openings. Quasi-vertical Schottky diodes on these pillars exhibit low N-D-N-A = 5.2 x 10(16) cm(-3), V-BD = 393 V, and a critical electric field E-C = 2.63 MV cm(-1).