Selective lateral etching of InAs/GaSb tunnel junctions for mid-infrared photonics

We have studied selective etching of the InAs/GaSb tunnel junction (TJ). We show that efficient lateral etching can be achieved with a citric acid:hydrogen peroxide solution. A slight etching anisotropy of around 10% is observed between [1 1 0] and [1 0 0] crystal orientations. The electrical properties of etched TJs do not depend on the diameter of the device which reveals efficient passivation and the absence of current leakage. Specific resistivities in the 2–5 × 10−5 Ω cm−2 range are measured even for diameters compatible with vertical-cavity surface emitting lasers. This work demonstrates that selective lateral etching of an InAs/GaSb tunnel junction is an efficient means to confine the current in GaSb-based heterostructures. (paper)