Surface Passivation Applicable to InAsSb/GaSb Photodiodes for Infrared Detection

In this paper the influence of various anodisation solutions on the surface passivation of InAsSb/GaSb photodiodes is examined. The diode structure is based on a design reported by Bubulac et al. [1]. The diode consists of a p-i-n structure grown by MOCVD and nearly lattice matched to a GaSb substrate. The structure, p-InAs1-xSbx/n-InAs1-xSbx/n-GaSb (x = 0.10 in both cases), consisted of a Zn-doped p-type layer and an unintentionally doped n-type layer on the n-type substrate. To define the active area of the photodiode, mesas were etched with a sulphuric acid based solution. Three anodisation solutions, containing Na2S, KOH or (NH4)2S, were tested. Four sets of diodes were processed, using each of the three anodisation solutions as well as an unpassivated reference detector. The effect of passivation was studied by current-voltage measurements, yielding the reverse bias current, as well as by responsivity measurements.