Characteristics of gradually doped LWIR diodes by hydrogenation |
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Authors: | Young-Ho Kim Tae-Sik Kim D A Redfern C A Musca Hee Chul Lee Choong Ki Kim |
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Affiliation: | (1) Department of Electrical Engineering, and Center for Electro-Optics, Korea Advanced Institute of Science and Technology, 373-1, Kusong-Dong, Yusong-Gu, 305-701 Taejon, Korea;(2) Semiconductor R&D Center, KEC Research Institute of Technology, Korea Electronics Co. Ltd., 149 Gongdan 1-Dong, Kumi, 730-031 Kyungbuk-Province, Korea;(3) University of Western Australia, Perth, Australia |
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Abstract: | The hydrogenation effects on HgCdTe diode performance are presented and the mechanism of hydrogenation is revealed. By the
hydrogenation, R0A is increased by 30 times and photo-response is also improved. It is supposed that these are explained by the increased minority
carrier lifetime by the hydrogenation. However, it is found from LBIC measurements that the minority carrier lifetime doesn’t
increase by the hydrogenation. An important clue that explains the hydrogenation effects is found from Hall measurements.
It is found that, after the hydrogenation, the doping concentration of Hg-vacancy doped substrate decreases and the mobility
increases. For the heavily hydrogenated bulk substrate, it is also found that the hydrogen passivates the whole Hg-vacancy
and reveals the residual impurity and p-type doping concentration is exponentially graded. From these measurements, the diffusion
current model of gradually doped diode is proposed. This model shows that the diffusion current of the graded junction diode
is 2 orders of magnitude smaller than that of the abrupt junction diode, which clearly explains the R0A increase by the hydrogenation. Medicisimulation to investigate the change of LBIC signal by the doping grading also coincides
with the measurements. From these measurements and model, the hydrogenation effects are attributed to the grading of Hg-vacancy
doped p-type substrate by the diffused hydrogen. |
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Keywords: | HgCdTe hydrogenation LWIR photodiode R0A LBIC Hall doping grading Hg vacancy |
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