QUANTUM WELL AND MODULATION DOPED GaAs - Gal-xAlxAs HETEROSTRUCTURES

MOVPE est appliqué à la réalisation de puits quantiques Ga1-xAlxAs - GaAs. Des puits aussi étroits que 25 Å sont obtenus. La qualité des interfaces est caractérisée par photoluminescence en fonction de la raideur des transitions de concentration d'aluminium. Aucun désordre d'alliage n'est observé. On met en evidence un accord remarquable entre les énergies de transition électron-trou lourd (n = 1) et celles calculées à partir d'un simple modèle de puits rectangulaire. Les résultats montrent que la transition GaAlAs-GaAs s'effectue en moins de 5 Å. Des hétérostructures à dopage modulé ont été obtenues dans des conditions de croissance similaires. Des résultats préliminaires sur la mobilité de Hall et des caractéristiques de TEC seront présentés.Ga1-xAlxAs - GaAs quantum wells are grown by MOVPE. Wells as narrow as 25 Å are made. Interface quality in relation to alloy clustering and abruptness in change of Al-content is characterized with the aid of luminescence spectrum measurements. A remarkable agreement is found between the experimental n = 1 electron to heavy hole transition energies and those which are calculated with the simple rectangular well model. The results indicate that the Al content changes at the interfaces over less than are unit cell. Modulation doped heterostructures were made in the same growth conditions as used for the quantum well growth. Results of Hall mobility measurements and preliminary FET characteristics are shown

Cyclotron resonance from the far-infrared transmission and the photoconductivity of a two-dimensional electron gas in a GaAs/AlGaAs heterojunction

Cyclotron resonance is investigated in far-infrared transmission and in photoconductivity measurements on a two-dimensional electron gas in an AlGaAs/GaAs heterojunction. The photoresistivity signal, divided by the temperature coefficient of the resistivity, displayed as a function of magnetic field, reproduces quite well the cyclotron resonance line observed in transmission. There is a slight difference in line width, which may be due to a shorter scattering time for localized as compared to non-localized electrons