Degradation Mode Analysis on Highly Reliable Guardring-Free Planar InAlAs Avalanche Photodiodes

摘要

This paper presents the high reliability of the guardring-free planar InAlAs avalanche photodiode (APD) and its degradation mode analysis. We have conducted long-term and high-temperature aging tests under 175 $^{circ}hbox{C}$, 200 $^{ circ}hbox{C}$, 225 $^{circ}hbox{C}$, and 250 $^{circ}hbox{C}$. There were three degradation modes as follows: 1) the increase in the dark current; 2) the decrease in the breakdown voltage; and 3) short circuit. Their thermal activation energies were 0.96, 1.30, and 0.93 eV, respectively. Their estimated mean times to failures at 85 $^{circ}hbox{C}$ are 25, 100, and 22 million hours, respectively. Increased dark current is generated in the upper side of the absorbing layer. The breakdown voltage decreased with aging time because the depletion width in the absorbing layer shrinks from the $hbox{p}+$ region side. Any degradation mode on the surfaced p-n junction did not appear in spite of the 10 000-h aging test at a high temperature of 200 $^{circ}hbox{C}$. The guardring-free planar InAlAs APD has the advantage of high reliability because the electric field of a surfaced p-n junction is weakened by the underlying field control layer.