DEEP LEVELS, ELECTRICAL AND OPTICAL CHARACTERISTICS IN SNTE-DOPED GASB SCHOTTKY DIODES

The GaSb layers investigated were grown directly on GaAs substrates by molecular beam epitaxy (MBE) using SnTe source as the n-type dopant. By using admittance spectroscopy, a dominant deep level with the activ ation energy of 0.23-0.26 eV was observed and its concentration was af fected by the Sb-4/Ga flux ratio in the MBE growth. A lowest deep-leve l concentration together with a highest mobility was obtained for GaSb grown at 550 degrees C under a Sb-4/Ga beam equivalent pressure (BEP) ratio around 7, which should correspond to the lowest ratio to mainta in a Sb-stabilized surface reconstruction. In the Hall measurement, an analysis of the temperature-dependent mobility shows that the ionized impurity concentration increases proportionally with the sample's don or concentration, suggesting that the ionized impurity was introduced by an SnTe source. In addition, optical properties of an undoped p-, a lightly and heavily SnTe-doped GaSb layers were studied by comparing their photoluminesence spectra at 4.5K.