Verify the bias dependence of quantum efficiency and identify avalanche onset

Determine whether the quantum efficiency of the IBEX HgCdTe linear-mode avalanche photodiode array continues increasing up to approximately 6 V, and precisely identify the pixel bias at which avalanche multiplication begins and the bias above which the quantum efficiency becomes stable.

Background

The measured response of an IBEX detector is degenerate with respect to quantum efficiency, avalanche gain, and conversion gain. Leonardo expects the quantum efficiency to increase up to approximately 6 V, but the characterization reported in the paper cannot independently isolate the quantum-efficiency evolution from the avalanche gain and conversion-gain variations in this transition region.

Consequently, the exact onset of avalanche multiplication and the bias at which the quantum efficiency becomes stable remain undetermined. Resolving this uncertainty is important for interpreting the detector response and for obtaining unbiased estimates of the excess-noise factor at higher bias.