A photo-detector comprising: a photon absorbing layer comprising a semiconductor material having a first energy band gap a barrier layer comprising a second semiconductor material having a second energy band gap, said barrier layer comprises a superlattice structure comprising a plurality of repeated superlattice units formed with different compositions of InGaAlAsSb materials; and a passivation structure (ISPS) comprising at least one crystallized layer grown in situ on said barrier layer, lattice matching with the barrier layer and having a third energy band gap; one or more metal contacts defining pixels of said photo-detector are electrically coupled to said barrier layer at exposed regions of the barrier layer, at which said passivation structure is absent; and wherein said passivation structure (ISPS) comprises a material having a high density of surface states thereby forcing pinning of an equilibrium Fermi level of said passivation structure to be within said third energy band gap and away from the conduction and valence bands of the barrier layer, thereby reducing surface leakage and preventing electrical conduction between the one or more metal contacts defining the pixels of said photo-detector; wherein said second energy band gap is larger than said first energy band gap such that application of an operating bias voltage of a certain electric polarity to said metal contacts causes attraction of minority carriers from said un-depleted photon absorbing layer across depleted regions of the barrier layer to said metal contacts; wherein said metal contacts coupled to the barrier layer form a Schottky junction/contact which collects minority carriers leaving the barrier layer; wherein the passivation structure (ISPS) includes a cap layer (CAPL) comprising said material having said high density of surface states, and wherein said material in the cap layer comprises a thin bulk layer of InGaAlAsSb a photon absorbing layer comprising a semiconductor material having a first energy band gap a barrier layer comprising a second semiconductor material having a second energy band gap, said barrier layer comprises a superlattice structure comprising a plurality of repeated superlattice units formed with different compositions of InGaAlAsSb materials; and a passivation structure (ISPS) comprising at least one crystallized layer grown in situ on said barrier layer, lattice matching with the barrier layer and having a third energy band gap; one or more metal contacts defining pixels of said photo-detector are electrically coupled to said barrier layer at exposed regions of the barrier layer, at which said passivation structure is absent; and wherein said passivation structure (ISPS) comprises a material having a high density of surface states thereby forcing pinning of an equilibrium Fermi level of said passivation structure to be within said third energy band gap and away from the conduction and valence bands of the barrier layer, thereby reducing surface leakage and preventing electrical conduction between the one or more metal contacts defining the pixels of said photo-detector; wherein said second energy band gap is larger than said first energy band gap such that application of an operating bias voltage of a certain electric polarity to said metal contacts causes attraction of minority carriers from said un-depleted photon absorbing layer across depleted regions of the barrier layer to said metal contacts; wherein said metal contacts coupled to the barrier layer form a Schottky junction/contact which collects minority carriers leaving the barrier layer; wherein the passivation structure (ISPS) includes a cap layer (CAPL) comprising said material having said high density of surface states, and wherein said material in the cap layer comprises a thin bulk layer of InGaAlAsSb