Sb-heterostructure millimeter-wave zero-bias diodes

Millimeter wave detection at W-band and above has great potential for imaging under a variety of environmental conditions such as precipitation, smoke, and dust. One current limiting factor is the large per pixel cost of arrays. Direct detecting zero bias diodes would reduce the cost significantly. Here, we demonstrate specially designed Sb-heterostructure-based backward diodes grown by molecular beam epitaxy. These diodes have superior frequency response compared to Ge diodes. The behavior is based on heterojunction tunneling and, in contrast to planar doped barrier (PDB) diodes, is not overly sensitive to growth conditions. Estimates indicate frequency operation comparable to or superior to PDB diodes should be achievable. Millimeter wave detector arrays containing thousands of diodes are now feasible for the first time at W-band and above. We present measurements demonstrating this performance and estimate the ultimate frequency potential of this new technology. The material system used is the InAs-AlSb-GaAlSb nearly lattice matched combination.