Surface leakage reduction in narrow band gap type-II antimonide-based superlattice photodiodes

Inductively coupled plasma (ICP) dry etching rendered structural and electrical enhancements on type-II antimonide-based superlattices compared to those delineated by electron cyclotron resonance (ECR) with a regenerative chemical wet etch. The surface resistivity of 4× 105 Ω cm is evidence of the surface quality achieved with ICP etching and polyimide passivation. By only modifying the etching technique in the fabrication steps, the ICP-etched devices with a 9.3 μm cutoff wavelength revealed a diffusion-limited dark current density of 4.1× 10-6 A/ cm2 and a maximum differential resistance at zero bias in excess of 5300 Ω cm2 at 77 K, which are an order of magnitude better in comparison to the ECR-etched devices.