Distinguish the physical origin of the reverse diode

Determine whether the reverse-diode behavior observed in InAlAs/InGaAs valley photovoltaic devices originates from the InGaAs/InAlAs heterojunction barrier, from intervalley scattering between the InGaAs Γ and L valleys, or from a combination of both mechanisms.

Background

The equivalent-circuit model attributes the S-shaped current–voltage response and the saturation of bias-dependent photoluminescence to a reverse diode. The paper analyzes two limiting physical explanations: thermionic emission across the InGaAs/InAlAs heterojunction when carriers are extracted from the Γ valley, and intervalley scattering between the Γ and L valleys when carriers are extracted from the L valley.

Poisson/drift-diffusion simulations show that both mechanisms can generate reverse-diode-like behavior and that the equivalent circuit fits both scenarios. Consequently, the available electrical and photoluminescence data do not uniquely identify which microscopic process is responsible, leaving the mechanism-discrimination problem unresolved.

References

The equivalent circuit fits to the PDD results are good in both scenarios (i) and (ii), indicating that both HJ and VS can produce the reverse diode in our circuit, and we cannot easily distinguish the mechanisms.

— Combined photoluminescence and electrical characterization of valley photovoltaic devices explained with an equivalent circuit  (2609.37854 - Xia et al., 29 Sep 2026) in Section “Physical meanings of circuit elements,” subsection “Origins of the reverse diode”