Analysis of InGaAs/InP p-I-n Photodiode Failed by Electrostatic Discharge

We have evaluated InGaAs/InP PIN (p-I-n) photodiodes failed by electrostatic discharge (ESD) with forward or reverse biasing, using scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), energy dispersive x-ray spectrometry (EDX), Raman spectroscopy, and photoluminescence (PL) imaging. First, localized traces and bumps were observed on the surface of the Au electrode by SEM. Next, by cross-sectional STEM observation, a heavily damaged region including a void was observed in the p⁺-InP layer and an upper part of the n⁻-InGaAs layer just below the bump on the Au electrode. Cross-sectional EDX mapping indicated that the damaged region consists of a mixture of InP and InGaAs, i.e., InGaAsP quaternary material. In addition, poor crystal quality of the active PIN region was also revealed by Raman spectroscopy and PL imaging. Furthermore, although similar results were obtained for the ESD-failed samples with application of both forward and reverse bias, the magnitude of the ESD damage is larger in the case of forward bias as compared with the case of reverse bias. On the basis of these results, we propose a possible ESD failure mechanism that is associated with significant Joule heating in the p⁺-InP layer and the upper part of the n⁻-InGaAs layer due to the local concentration of a large current.