27 August 2009 Al fraction induced effects on the capacitance characteristics of n+-GaN/AlxGa1-xN IR detectors
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Capacitance-voltage-frequency measurements on n+-GaN/AlxGa1-xN Heterojunction Interfacial Workfunction Internal Photoemission (HEIWIP) detectors were used to analyze the effects of Al fraction induced heterojunction barrier and its effect on the electrical characteristics at the heterointerface. The detector's IR threshold can be modified by changing the barrier Al concentration. A sample with an Al fraction of 0.1 shows a distinct capacitance step and capacitance hysteresis, which is attributed to N-vacancies and/or C-donor electron trap states located just above the Fermi level (200 meV) at the GaN/AlGaN interface, with activation energies of 149±1 and ~189 meV, respectively. A sample with an Al fraction of 0.026 showed negative capacitance and dispersion, indicating interface electron trap states located below the Fermi level (88 meV), most likely due to C-donor and/or N-vacancy with activation energies of 125±1 and 140±2 meV, respectively. Additional impurity related absorption centers were identified in both samples, however these shallow Si-donor sites (~30.9±0.2 meV) did not affect the capacitance as these states were located in the barrier layer and not in the vicinity of the Fermi level. The Al fraction in the barrier layer was found to significantly change the positions of the interface trap states relative to the Fermi level, resulting in the observed capacitance characteristics.
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Laura E. Byrum, Gamini Ariyawansa, Ranga Jayasinghe, Nikolaus Dietz, A. G. Unil Perera, Steven G. Matsik, Ian T. Ferguson, Andrew Bezinger, Hui Chun Liu, "Al fraction induced effects on the capacitance characteristics of n+-GaN/AlxGa1-xN IR detectors", Proc. SPIE 7467, Nanophotonics and Macrophotonics for Space Environments III, 74670W (27 August 2009); doi: 10.1117/12.828156; https://doi.org/10.1117/12.828156


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