Room Temperature 3.5- $\mu \text{m}$ Mid-Infrared InAs Photovoltaic Detector on a Si Substrate

We report a mid-infrared InAs p-i-n photovoltaic detector on a Si substrate operating at room temperature with a cutoff wavelength at 3.5 μm. The large 11.6% lattice mismatch between the device layer (InAs) and the Si substrate is accommodated by employing a compositionally graded buffer layer technique using solid-source molecular beam epitaxy and a commercially available GeSi substrate. An Al
_x
In
_1-x
As graded buffer layer is used to linearly scale the lattice constant from AlAs to InAs with an increasing x value. The photovoltaic detector has a responsivity of 0.57 A/W, measured using a blackbody source maintained at 700 °C.