Highly Sensitive Photodetector Using Ultra-High-Density 1.5-μm Quantum Dots for Advanced Optical Fiber Communications

We have fabricated a high-density 1.5-μm quantum dot photodetector for advanced optical fiber communications and have found unique optical properties, including avalanche multiplication. The structure of the absorption layer had stacked InAs/InGaAlAs layers with a high density of 1 × 10
¹²
cm
^-2
, which consisted of strained 1.5-μm InAs quantum dots and a strain compensation layer of InGaAlAs. A three times larger absorption coefficient than the InGaAs layer, an avalanche multiplication effect, and a low dark current are reported with InAs quantum dot conditions.