Investigation of surface leakage current in MWIR HgCdTe and InAsSb barrier detectors

Abstract

In this paper we have investigated dark current sources in high-operating temperature HgCdTe p B nN p + + and InAsSb p B nn p + + and p B nN p + + barrier infrared detectors fabricated using metal organic chemical vapour deposition and molecular beam epitaxy, respectively. The bulk leakage and surface leakage components of the dark current were determined for unpassivated devices fabricated in a round mesa geometry and in different sizes, from 100 to 500 μm diameters. Results show that the surface leakage current depends on both the conductivity types of the active layers and the semiconductor surfaces. In the InAsSb p B nn p + + detector the bulk component constitutes 100% of the total dark current flowing through the heterostructure. Since the absorber region has the same conductivity type in its bulk and at its surface, the unipolar barrier blocks the current in the bulk, and also blocks the current along the n-type surface of the device. For the HgCdTe p B pN p + + detector, the bulk component constitutes about 50% of the total dark current density in the 200 μm device operating at 230 K and −0.1 V, whereas for the InAsSb p B pN p + + detector this share is much higher and amounts to 98%. In the HgCdTe detector, the surface leakage current is attributed to the sidewall surfaces along the absorber, as well as depleted surface. In InAsSb, the surface states are pinned into the conduction band, thus the surface current is limited and comes mainly from the depleted area.

Diffusion-limited dark currents in mid-wave infrared HgCdTe-based nBn structures with Al2O3 passivation

“…The surface leakage current determined the total dark current of previously described first-iteration structures based on MBE HgCdTe [15]. The obtained results show that, in nBn structures based on MBE HgCdTe with passivation of the PE ALD Al 2 O 3 film, the surface leakage current [37][38][39] can be suppressed.…”

Antimonide-based high operating temperature infrared photodetectors and focal plane arrays: a review and outlook

“…It occurs at sites within the bandgap for MCT materials, leading to a nondegenerate n-type surface, while for InAs and InAsSb, it falls in the CB, so a large number of electrons accumulate close to the sidewall, which creates a highly conductive n-type surface. This process is regardless of the bulk material doping type [55], as illustrated in figure 3(c). When the conductivity type of the bulk material is identical to that at the surface, the majority carriers leak along the mesa sidewall into the contact layer.…”

Advances in type-II superlattice research at Fraunhofer IAF

“…Due to interdiffusion processes during HgCdTe growth, the x-graded regions were created at heterojunction interfaces. Figure 4 shows the schematic design and calculated band profiles for the p + BppN + photodiode operating at zero and 0.5 V reverse bias voltage and 230 K [13]. Calculations were made with the commercially available software APSYS.…”

“…Calculated band diagrams at 230 K for a HgCdTeheterostructure photodiode operated at zero and reverse bias voltage. After Ref [13]…”