Analysis of hydrogenation effects on LWIR HgCdTe diode characteristics

In this work, we demonstrate how Hg_0.78Cd_0.22Te photovoltaic detectors are affected by the hydrogenation technique. To examine the effects of hydrogenation, n on p type photovoltaic diodes were fabricated with the undoped wafers having a cutoff wavelength of 10.5 μm. The hydrogenation was performed in a simple parallel-plate plasma equipment. The zero bias dynamic resistance area product (RoA) of the hydrogenated diodes are found to be 70 ~120 Ωcm², which is one order of magnitude higher than that of non-hydrogenated diodes. From the model fitting analysis, the hydrogenation effects were attributed to an increase of the minority carrier lifetime and a decrease of the trap density in the depletion region. The quantum efficiency also increased with the hydrogenation, which is revealed in the spectral current response and the photocurrent of hydrogenated diode. Laser beam induced current (LBIC) measurements were also undertaken to understand the mechanism of the hydrogenation. It was found that the peak LBIC signal obtained from the hydrogenated diode was two times larger than that of non-hydrogenated diode, which supports the theory of reduced trap density in the depletion region due to the hydrogenation. It is concluded that the hydrogenation process improved the junction property as well as the bulk property