Excess noise in MWIR photovoltaic detectors fabricated using a new junction formation technology

The current-voltage characteristics measured over a wide temperature range are reported for HgCdTe mid-wavelength IR n-on-p photodiodes fabricated using a novel junction formation technology. The planar homojunction device junctions were formed on LPE grown vacancy doped HgCdTe using a reactive ion etching (RIE) plasma induced conversion process. The zero bias dynamic resistance - junction area product, RoA, was 4.6 X 107 (Omega) .cm2 at 80K an is comparable to the best planar diodes reported using conventional and significantly more complicated ion implantation junction formation technology. Arrhenius plots of RoA exhibit an activation energy equal to the bandgap, Eg, and show that the diodes are diffusion limited for temperatures >= 130K. In order to further compare this junction formation technology to other techniques, a series of temperature dependent 1/f noise measurements were performed. Form this study the activation energy for 1/f noise in the region where the diodes are diffusion limited was found to be 0.7Eg. Energies close to this value have previously been associated with Hg vacancies in HgCdTe. These results are similar to those obtained from high quality HgCdTe photodiodes fabricated using mature ion implantation technology. However, the plasma based technology used in this work is significantly less complex and does not require any high temperature annealing steps.