Effect of a valence-band barrier on the quantum efficiency and background-limited dynamic resistance of compositionally graded HgCdTe P-on-n heterojunction photodiodes

A new analytical model for the bias-dependent quantum efficiency of a HgCdTe P-on-n heterojunction photodiode with a valence band barrier elucidates the important physics of the phenomenon and shows that the background-induced shunt resistance is a result of the same mechanism, that is, a tendency of the light-induced carriers to pile up in the base layer due to the retarding field produced by the barrier. A parameterized version of the model agrees well with experimental current-vs-voltage and noise measurements.