Electrical and optical characterization of metastable deep-level defects in GaAs

Two metastable defect configurations, here designated M3 and M4, are observed in n-type GaAs grown by metal organic chemical-vapor deposition. The configurations are comprehensively characterized by deep-level transient spectroscopy and have enthalpies for thermal emission of electrons of 0.6 and 0.3 eV, respectively. The metastable transformation between these two centers is found to be temperature induced and bias controlled. The capture cross sections for both defect configurations are found to be temperature independent with values of 5.1×{}10^-18 and 1.8×{}10^-18 cm² for the M3 and M4 configurations, respectively. Defect depth profiling shows defect densities that decrease monotonically from approximately 1×{}10¹³ cm^-3 at 0.2 {μ}m below the surface to approximately 1×{}10¹¹ cm^-3 at 0.6 {μ}m below the surface for both defect configurations. Photocapacitance measurements give photoionization threshold energies consistent with the electrical measurements and photoionization cross sections of about 2×{}10^-19 cm² at a photon energy of 0.75 eV. The complete metastable reaction kinetics are also reported, as well as the electric field dependence of the emission rate for each configuration.