OPTICALLY STIMULATED INTERSUBBAND ABSORPTION IN UNDOPED AMORPHOUS SI SIO2 QUANTUM-WELL

Intersubband absorption has been observed in undoped amorphous multipl e-quantum-well (MQW) strucctures under interband excitation. The trans itions take place between the first and second subbands of the conduct ion 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 relaxatio n of the electron momentum conservation in the QW plane. The high join t density of states end oscillator strength for the intersubband trans itions in amorphous QWs allow one to observe the absorption at low ele ctron concentrations (N-e approximate to 10(13) cm(-3)) in the ground conduction subband.