Photoelectric properties of HgMnTe photodiodes with ion etched p-n junctions
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Thotodiodes with p-n junctions formed by ion etching of p-Hg1-xMnxTe (x ≈1) are reported. The multielement photodiode arrays for mid-infrared region were fabricated using surface passivation, photolithography and three-layer metallisation processes. The absorption curves of the crystals found from optical measurements are treated within the Kane theory for semiconductors with highly nonparabolic energy bands. The parameters of the diodes are obtained from their electrical study. It is shown that due to strong degeneracy of the n+ - layer the Hg1-xMnxTe diode structure can be considered as one-sided abrupt n+ -p junction with the barrier height larger significantly than the semiconductor bandgap. The diode responsivity spectra are interpreted in the framework of model taking into account the generation of photocarriers in n+ - and p-regions as well as in the depletion layer. The diode photoresponsivity in the region of the photon energies below semiconductor bandgap is shown to be caused by the gentle slope of the observed absorption edge. Temperature measurements reveal essential peculiarities of carrier tunnelling in the diodes. Invoking the general expression for the tunnelling probability and taking into consideration the opposing flow of electrons allow the observed tunnelling decay at low reverse biases to be explained. The zero bias resistance-area product (RoA) for the Hg1-xMNxTe diodes with cutoff wavelengths 7-8 and 10-11um amount up to 20-30 and ~ 500 Ω cm2, respectively, indicating the photodiodes under study to be competitive with Hg1-xCdxTe photovoltaic detectors.
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