| The 2DES in InAs MOS space charge layers is studied with infrared and farinfrared spectroscopy. Intersubband resonances and cyclotron resonances are the most characteristic excitations of quasi 2DES. The intersubband frequency is tuned by a gate voltage, and the Landau level frequency is tuned by amagnetic field to coincide with a fixed laser frequency. The following main topics are experimentally studied and are thoroughly discussed in this dissertation: (1) for the first time, the motional binding effect was directly observed in FIR intersubband transition spectra in InAs accumulation layer; (2) due to the non-parabolic InAs MOS system, the combined intersubband cyclotron resonances were observed in the perpendicular magnetic field; (3) inversion layer intersubband resonance spectra reveal the subband spacing, which is in good agreement with our self-consistant calculation; (4) the line-shape of intersubband resonance absorption of InAs MOS quantum wells in accumulation and inversion layers for different carrier concentration; (5) the spectra in magnetic field parallel to the sample surface show a kind of inhomogeneous intersubband resonance absorption, this is demonstrated by the two different sorts of resonance lineshape, one is shifting, while the other is broadening. |
