DEEP LEVELS IN BULK LEC SINGLE-CRYSTAL INXGA1-XAS

Bulk single crystals of In(x)Ga(1-x)As (0.01 < x < 0.12) were successfully grown by the Liquid Encapsulated Czochraski (LEC) technique. These crystals are of high quality and can provide tunable substrate material for epitaxial application, since the lattice constant may be adjusted by varying the composition. Nominally undoped crystals were semi-insulating as grown if x is less than about 0.05. Semi-insulating crystals with higher In composition can be obtained by chromium doping during crystal growth. The as-grown crystals were studied by 4.2 K photoluminescence spectroscopy (PL) and thermally stimulated current spectroscopy (TSC). Results from PL measurements indicate good crystal quality and impurity control. TSC spectra reveal several bulk traps in undoped and Cr doped semi-insulating samples. The activation energies of these traps decrease as In composition is increased. The amount of change in activation energy is about one third of the bandgap shrinkage due to increased In concentration.