INTERSUBBAND ABSORPTION IN SB DELTA-DOPED MOLECULAR-BEAM EPITAXY SI QUANTUM-WELL STRUCTURES

Strong electron intersubband infrared absorption near the 10-mu-m wavelength is observed in Sb delta-doped Si multiple quantum wells grown on (100) Si substrate. The structure used for measurements consists of five periods of Sb delta-doped Si quantum wells and undoped Si barriers. An infrared absorption of 82% is measured with a Fourier-transform infrared spectrometer using a waveguide structure with ten internal reflections. Sb delta-doped layers with sharp and high doping profiles for the quantum wells are obtained by modulating the substrate temperature between 300 and 600-degrees-C during molecular beam epitaxy growth. Absorption peaks ranging from 5.8 to 8.1-mu-m are observed. The peak positions can be tuned by changing the doping concentration in the quantum wells. The observed polarization angle dependence agrees with the intersubband selection rule for (100) Si, i.e., X-like valley.