Characterization of HgCdTe p-on-n heterojunction photodiodes and their defects using variable-area test structures

Abstract

Variable-area diodes are routinely used to separate surface from bulk effects in the characterization ofHgCdTe photodiodes. In this work, the traditional models are reviewed and clarified by comparison to the results of numerical models of diffusion and other effects. It is shown that the characteristic lengths associated with lateral collection of both thermal and photo-generated carriers are not necessarily equal to each other and also are not equal to the minority carrier diffusion length. The effective surface recombination velocity in the traditional model for surface generation-recombination current is shown to have an alternative explanation as the effect of a surface inversion channel. Finally, the relation of the traditional models to the effects of point defects is examined. The average effects of defects with bulk or surface distributions are shown to contribute either zero or positive slope, respectively, in a plot of the inverse of the zero-bias resistance-area product vs the perimeter to area ratio. A negative slope arises from defects whose conductance increases faster than linearly with the diode radius. Distributions of diode dynamic resistance data from over 100 HgCdTe test arrays were analyzed to determine how the probability of a diode being defective varies with diode size. Plots of the diode conductance data ordered by increasing conductance indicate that the onset of defects occurs for a percentage of diodes of a given size which increases approximately linearly with the diode perimeter. This suggests that these defects have a perimeter rather than bulk origin.

Proton Irradiation Effects on the Performance of III-V-Based, Unipolar Barrier Infrared Detectors

“…Other studies have shown is dependent on junction depth, surface recombination velocity and the absorption coefficient, as well as on the minority carrier diffusion length ; therefore, should only be treated as a phenomenological fitting factor that represents an effective diffusion length. [10] [11] Judging by the fit qualities of the measurements in these experiments referred to, (1) appears to be a valid means of assessing the optical response of these detectors even as was expected to decrease below the absorber length with increasing proton fluence . Both optical and electrical characterization results for several of the PECs presented in this work were compared to that of companion FPAs and there was strong agreement between those results.…”

“…As described in [10] [11], is expected to be roughly proportional to , however, their relationship is not specifically linear.…”

“…Formally, damage factor analysis typically only considers linear changes with and thus, formally-speaking, it is that should be examined for , where related to by (10) of a non-ideal nBn is considered next. If a depletion region of width exists in the detector's narrow gap layer, due either to the detector's design or from operating at a slightly higher than intended reverse bias voltage, then a generation-limited dark current density component , given by (11) will also be present. [1] For , changes to the generation time with must now be considered.…”

Advances in composition control for 16 µm LPE P-on-n HgCdTe heterojunction photodiodes for remote sensing applications at 60K

“…4). The lateral optical collection length, L opt , which is related to the minority carrier hole diffusion length, 11 followed the same trend as the quantum efficiency with temperature. Current-voltage curves at different temperatures and R o A as a function of temperature are shown in Fig.…”

Radiation Damage in Type II Superlattice Infrared Detectors

“…Note that L c is generally smaller than the radial diffusion length by an amount that depends on the device geometry, built-in voltage, and surface recombination. 16 For the hybrid devices, L c (0) is about 24 lm. This is consistent with an in-plane diffusion length substantially greater than the growth-direction diffusion length, L z (0).…”