Characterization of p-i-n Particle Detectors Based on Semi-Insulating GaAs with an MOCVD-Grown P⁺ GaAs Anode Contact Layer

Semi-insulating (SI) gallium arsenide (GaAs) alpha detectors with anode GaAs P+ contact layer were fabricated and characterized. The contact layer growth was carried out by metal-organic chemical vapor deposition (MOCVD) and the detector performances were compared to the performances of a front Schottky contact detector. The front-side Schottky contact suffers from electron injection into the GaAs substrate. This injection is eliminated by using a P+ anode blocking layer with an ohmic contact, resulting in a reduction of leakage current at reverse bias values of up to 70 V. For example, at 30 V, the leakage currents were 50 and 150 nA/cm2 for the ohmic and the Schottky anode detectors, respectively. For both detectors, the charge collection efficiency (CCE) was increased by a factor of ~2 after grinding the substrates from 650- to 310-$\mu $ m thickness, with no leakage current degradation. In addition, rapid thermal process (RTP) annealing of the bottom N contact reduced the leakage current only for the Schottky detector, while improving the forward bias characteristics for both ohmic and Schottky detectors, as expected.