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

A low voltage (&minus
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 &times
1014 /cm3) metalorganic vapor phase epitaxy (MOVPE) grown 15 &micro
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 &micro
m)-based Schottky barrier diodes (SBD) at &minus
20 V. This is the first report of &alpha
&ndash
particle detection at 5.48 MeV with a high CCE at &minus
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 &minus
120 V to &minus
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 &minus
300 V.