Low Voltage High-Energy α-Particle Detectors by GaN-on-GaN Schottky Diodes with Record-High Charge Collection Efficiency

A low voltage (-20 V) operating high-energy (5.48 MeV) alpha-particle detector with a high charge collection efficiency (CCE) of approximately 65% was observed from the compensated (7.7 x 10(14) /cm(3)) metalorganic vapor phase epitaxy (MOVPE) grown 15 mu m thick drift layer gallium nitride (GaN) Schottky diodes on free-standing n+-GaN substrate. The observed CCE was 30% higher than the bulk GaN (400 mu m)-based Schottky barrier diodes (SBD) at -20 V. This is the first report of alpha-particle detection at 5.48 MeV with a high CCE at -20 V operation. In addition, the detectors also exhibited a three-times smaller variation in CCE (0.12 %/V) with a change in bias conditions from -120 V to -20 V. The dramatic reduction in CCE variation with voltage and improved CCE was a result of the reduced charge carrier density (CCD) due to the compensation by Mg in the grown drift layer (DL), which resulted in the increased depletion width (DW) of the fabricated GaN SBDs. The SBDs also reached a CCE of approximately 96.7% at -300 V.