Photocapacitance (PHCAP) and Hall effect measurements are applied to liquid-phase epitaxially grown n-Al0.3Ga0.7As crystals, followed by an annealing at 900°C for 1 h under controlled arsenic vapor pressure. Photocapacitance measurements reveal two deep levels in relatively lightly Te-doped samples, the optical activation energy of which are 0.5 and 1.1 eV, respectively (Ec-0.5 eV level and Ec-1.1 eV level). The Ec-0.5 eV level density increases with applied arsenic vapor pressure during annealing. The Ec-1.1 eV level density increases with increasing arsenic vapor pressure, but decreases at the highest arsenic vapor pressures. Hall effect measurements show that activation ratio between carrier concentration and Te concentration is higher when the epitaxial layers are annealed under lower arsenic vapor pressure (0.2 Torr) than the samples annealed under higher arsenic pressure (310 Torr), and decreases in the heavily Te-doped samples. From these results, the origin of the defects detected in n-AlxGa1-xAs is discussed in view of deviation from the stoichiometric composition and Te doping in the AlxGa1-xAs ternary alloy system.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Renewable Energy, Sustainability and the Environment
- Surfaces, Coatings and Films
- Materials Chemistry