Optically stimulated intersubband absorption in undoped amorphous Si/SiO₂ qiantum well

Abstract

lntersubband absorption has been observed in undoped amorphous multiple-quantum-well (MQW) strucctures under interband excitation. The transitions take place between the first and second subbands of the conduction band and involve non-equilibrium electrons excited into the first subband by optical pumping. The absorption band FWHM of 0.1 eV is much larger than for crystalline MQWs, a fact which reflects the relaxation of the electron momentum conservation in the QW plane. The high joint density of states and oscillator strength for the intersubband transitions in amorphous QWs allow one to observe the absorption at low electron concentrations (Ne = 1013 cm -3) in the ground conduction subband.