Electrical characterization of PbTe p-n junctions for applicarion in infrared detectors. / Caracterização elétrica de junções p-n de PbTe para aplicação em detectores de infravermelho.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2004

RESUMO

This work reports on the electrical characterization of PbTe p-n junctions for application in photovoltaic detectors in the medium infrared range. For this purpose, a series of p-n junctions, where the hole concentration p was kept at 1017 cm-3 and the electron concentration n varied between 1017 and 1019 cm-3, was successfully grown by molecular beam epitaxy on barium fluoride substrates. A system to measure current versus voltage (IxV) and capacitance versus voltage (CxV) characteristics was employed together with data acquisition and control programs developed in Visual Basic platform. Using this experience, a Visual Basic code to control the molecular beam epitaxial system was also developed. Mesa diodes were fabricated by lithography and mounted in a liquid nitrogen cryostat for the electrical characterization and the determination of figures of merit (detectivity and spectral response). The results obtained by the CxV characteristic showed that for electron concentration n > 1018 cm-3, one-sided abrupt junctions were formed. In this case, the hole concentration and the depletion width could be determined. The IxV characteristic exhibited different forms for both reverse and direct branches, even for diodes fabricated from the same junction. The incremental differential resistance, the series and parallel resistances, the ideality factor of the diodes were obtained by the derivative of the IxV curve and by a simulation program developed to adjust the curve calculated by the equation for a real diode to the experimental data. The fluctuations observed for both the parameters obtained from the IxV curve analysis and detectivity D* values were attributed to problems during the photodiode fabrication processes. Despite of these fluctuations, it was possible to correlate the noise and detectivity values measured for the PbTe detectors to the parameters obtained form the IxV characterization. These results allow the prediction of the detector?s figures of merit from the data obtained from the IxV curves. It is also important to emphasize that the best PbTe photodiodes fabricated during this work showed D* values close to 1011 cmHz1/2W-1, comparable to InSb and HgCdTe commercial detectors and to PbTe photodiodes fabricated on silicon substrates.

ASSUNTO(S)

engineering and space technology engenharia e tecnologia espacial infrared detectors epitaxia de feixe molecular capacitance voltage characteristics teturetos de chumbo lead tellurides molecular beam epitaxy características da capacitância por tensão detectores de infravermelho

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