Modeling charge collection efficiency degradation in partially depleted GaAs photodiodes using the 1- and 2-carrier Hecht equations

• Published in: Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms Vol. 399; no. C; pp. 12 - 19
• Main Authors: Auden, E.C., Vizkelethy, G., Serkland, D.K., Bossert, D.J., Doyle, B.L.
• Format: Journal Article
• Language: English
• Published: United States Elsevier B.V 15-05-2017; Elsevier
• Subjects: Charge collection efficiency; Gallium arsenide; INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; Ion accelerators; Ion radiation effects; PARTICLE ACCELERATORS; Photodiodes; Charge collection efficiency; Ion radiation effects; Ion accelerators; Photodiodes; Gallium arsenide
• ISSN: 0168-583X; 1872-9584
• DOI: 10.1016/j.nimb.2017.03.045

The Hecht equation can be used to model the nonlinear degradation of charge collection efficiency (CCE) in response to radiation-induced displacement damage in both fully and partially depleted GaAs photodiodes. CCE degradation is measured for laser-generated photocurrent as a function of fluence and bias in Al0.3Ga0.7As/GaAs/Al0.25Ga0.75As p-i-n photodiodes which have been irradiated with 12MeVC and 7.5MeV Si ions. CCE is observed to degrade more rapidly with fluence in partially depleted photodiodes than in fully depleted photodiodes. When the intrinsic GaAs layer is fully depleted, the 2-carrier Hecht equation describes CCE degradation as photogenerated electrons and holes recombine at defect sites created by radiation damage in the depletion region. If the GaAs layer is partially depleted, CCE degradation is more appropriately modeled as the sum of the 2-carrier Hecht equation applied to electrons and holes generated within the depletion region and the 1-carrier Hecht equation applied to minority carriers that diffuse from the field-free (non-depleted) region into the depletion region. Enhanced CCE degradation is attributed to holes that recombine within the field-free region of the partially depleted intrinsic GaAs layer before they can diffuse into the depletion region.