Evidence of a conductive superficial layer, unintentionally generated by plasma etching, as the cause of high perimeter current on InGaAs photodiodes.

We report on the investigation of the origin of an apparent contradiction found in devices where passivation reduced significantly the superficial recombination but did not decrease the reverse dark current of mesa-type InGaAs photodiodes. The results show evidence of a conductive superficial layer formed during plasma etch, which shortens the device without generating a high recombination rate. The investigation was mainly done measuring the temperature dependence of this superficial dark current and performing TCAD simulation.