Luminescence studies of the 1.36-eV band and the edge emission in melt-grown GaAs : Cu

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Abstract
Using cathodoluminescence at 80–300 K, we have measured the injection‐level dependence, frequency response, and temperature dependence of the 1.36‐eV band and the 1.50‐eV edge emission in melt‐grown GaAs : Cu. The overall luminescence is relatively weak and the 1.36‐eV band is accompanied by a broad emission in the range 1–1.4 eV. We find no inherent injection‐level shift in the shape or peak energy of the 1.36‐eV band. With increasing temperature, the 1.36‐eV band quenches out with an activation energy of 0.1 eV or greater. The frequency response of the 1.36‐eV band is remarkably flat for deep‐center luminescence. However, the frequency response of the edge emission is unusually slow in GaAs : Cu, particularly in samples with higher Cu concentration. Variation in injection level causes a strong variation in branching between the 1.36‐eV band and the edge emission which is not explicable in terms of occupancy effects related to the relative kinetics of the two bands. It is suggested that the 1.36‐eV band results from a conduction‐band‐to‐acceptor transition whose kinetics are dominated by another process such as equilibration of a carrier trapping level in resonance with the conduction‐band continuum. The same process also controls the kinetics of the edge emission transition in GaAs : Cu with high Cu concentration.