Correlation of shunt resistance with InGaAs layer photoluminescence intensity for 2200 nm cutoff InGaAs photodiodes

This paper discusses techniques developed for predicting electrical properties of photodiodes fabricated from chloride vapor phase epitaxy-grown 2200 nm cutoff In_0.72Ga_0.28As/InAs_yP_1-y heterostructures with y compositionally graded from 0.0 - 0.4. Scanning electron microscopy (SEM) was used to examine the epitaxial layers in cross-section to determine their thickness uniformity over the wafer. Cross-sectional transmission electron microscopy (XTEM) was used to show that although strain in the structure was well accommodated within the InAs_yP_1-y graded layers, the cap, active and buffer layers were not completely lattice-matched to each other. In_0.72Ga_0.28As photoluminescence (PL) intensity data showed a strong dependence on the lattice-mismatch between the cap and active layers. Photodiode shunt resistance normalized to the active region area, R₀A, was found to increase dramatically with increasing PL intensity. We propose that PL intensity from the In_0.72Ga_0.28As layer on pre-processed wafers is a faithful measure of ultimate device performance.