PHOTOLUMINESCENCE STUDY OF GALLIUM ANTIMONIDE CRYSTALS GROWN BY VERTICAL BRIDGMAN METHOD

Undoped, In-doped and Te-doped gallium antimonide crystals were grown by the vertical Bridgman method and were characterised for defects by the photoluminescence (PL) method at 12 K using a 2.5 mW (0.633-mu-m) He-Ne laser as the optical source. PL spectra of undoped samples showed two peaks at 795 and 778 meV corresponding to the binding energies 0.015 and 0.032 eV. The 0.015 eV energy due to the acceptor impurity level was further verified by Hall effect measurements (0.012 eV) while the other energy, 0.032 eV, may be due to a bound-acceptor transition. The above two peaks drastically reduced for In-doped (5 x 10(19) cm-3) samples indicating a decrease in native defects due to isoelectronic doping. Te-doped samples (2.3 x 10(17) cm-3) showed broad emission bands which shifted to higher energy with increasing carrier concentrations, possibly due to a shift of the Fermi level towards the conduction band.