Long-term stability of GaSb/In(Al)GaAsSb thermophotovoltaic cells passivated by electrochemical treatment in sulphur containing solutions

Sulphur passivation effects on the performance of LPE-grown GaSb/InGaAsSb/AlGaAsSb photodiodes designed for TPV applications have been monitored within the period of 3 years. The applicability of (NH₄)₂S, Na₂S, and (NH₂)₂CS solutions have been compared by measuring of electro-optical characteristics (I-V, R_Gammalambda, eta-lambda) and investigating surface properties (X-ray photoelectron spectroscopy and variable angle spectroscopic ellipsometry). We show that electrochemical passivation enables to reduce photodiodes dark current, to increase their differential resistance by a factor of 4 and detectivity up to 2 times 10¹⁰ cmHz^1/2 W¹ and assures long-term stability of passivated surfaces.