Parameter evaluation in automated digital deep-level transient spectroscopy (DLTS)

A method of directly evaluating the activation energy Delta E, capture cross section sigma , and density N/sub T/, of deep-level traps from the pulsed reverse bias capacitance transient is described. The main advantages of this technique are that it requires only a single temperature scan, and it can resolve nonexponential transients due to closely-spaced energy levels. The test samples used for this paper consisted of Schottky diodes fabricated on nonirradiated and 1-MeV electron-irradiated n-type VPE (vapor-phase epitaxy) GaAs wafers. The well known EL2 trap was identified with Delta E of 0.81 eV, and sigma /sub n/ of 1.0*10/sup -13/ cm/sup 2/ for the nonirradiated sample. These values were found to be in good agreement with published data using established, conventional DLTS techniques. For the irradiated samples a nonexponential capacitance transient was found in the EL2 range of temperatures. The discussed technique was able to resolve two closely spaced deep levels lying at E/sub c/-0.81 eV and E/sub c/-0.84 eV, and with capture cross sections of 1.5*10/sup -13/ cm/sup 2/ and 2.5*10/sup -12/ cm/sup 2/, respectively.<
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