New metastable defects in GaAs

Two previously unreported metastable defects in n-type GaAs epitaxial layers grown by metalorganic chemical vapor deposition have been identified by deep level transient spectroscopy. These levels, here labeled M3 and M4, have activation energies for thermal emission of electrons of 0.31 and 0.61 eV, respectively. Formation of the M4 center and annealing of the M3 center are observed to take place when a reverse bias is applied to Schottky diodes at elevated temperatures. The reverse transition is observed under zero bias at elevated temperatures (e.g., 400 K). An additional metastable defect, labeled M2, with transformation properties similar to those of the M4 center and an emission activation energy of 0.64 eV, was observed in samples which received a rapid thermal anneal at temperatures of 900°C and above.