Long-wavelength stacked SiGe/Si heterojunction internal photoemission infrared detectors using multiple SiGe/Si layers

Utilizing low temperature silicon molecular beam epitaxy growth, long-wavelength stacked SiGe/Si heterojunction internal photoemission (HIP) infrared detectors with multiple SiGe/Si layers have been fabricated and demonstrated. Using an elemental boron source, high doping concentration (≊4×1020 cm−3) has been achieved and high crystalline quality multiple Si0.7Ge0.3/Si layers have been obtained. The detector structure consists of several periods of degenerately boron doped (≊4×1020 cm−3) thin (≤50 Å) Si0.7Ge0.3 layers and undoped thick (≊300 Å) Si layers. The multiple p+-Si 0.7Ge0.3/undoped-Si layers show strong infrared absorption in the long-wavelength regime mainly through free-carrier absorption. The stacked Si0.7Ge0.3/Si HIP detectors with p=4×1020 cm−3 exhibit strong photoresponse at wavelengths ranging 2–20 μm with quantum efficiencies of about 4% and 1.5% at 10 and 15 μm wavelengths, respectively. The detectors show near ideal thermionic-emission limited dark current characteristics.