Optimized InAlAs graded buffer and tensile-strained dislocation filter layer for high quality InAs photodetector grown on Si

Abstract

We demonstrate a low threading dislocation density (TDD) and smooth surface InAs layer epitaxially grown on Si by suppressing phase separation of InxAl1-xAs (x=0 to 1) graded buffer and by inserting a tensile-strained In0.95Al0.05As dislocation filter layer. While keeping the total III-V layer below 2.7 mu m to avoid thermal cracks, we have achieved a sixfold reduction of TDD in InAs on Si compared to the unoptimized structure. We found a strong correlation between the metamorphic InAs surface roughness and TDD as a function of InxAl1-xAs buffer thickness. An optimal thickness of 175nm was obtained where both phase separation and 3D islanding growth were suppressed. Moreover, a tensile-strained In0.95Al0.05As dislocation filter layer and high growth temperature of the InAs cap layer further assisted the dislocation reduction process, which led to a TDD to 1.37x10(8)cm(-2). Finally, an InAs p-i-n photodetector grown on the optimized InAs/Si template confirmed its high quality by showing an improved responsivity from 0.16 to 0.32A/W at a 2 mu m wavelength.