Deep-level transient spectroscopy study of n-type GaAs epitaxial layers grown by close-spaced vapor transport

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We have done a deep-level transient spectroscopy study of deep donor traps existing in n-type GaAs epitaxial layers grown by close-spaced vapor transport. All the samples exhibited a bulk trap having an important concentration (≳1014 cm−3), which we have noted ELCS1 and identified with the trap EL12, which was observed in vapor-phase epitaxy materials. Other bulk traps were observed in some samples, but in a weaker concentration (∼1013 cm−3). In other samples, in addition to ELCS1, two more traps were seen; their concentration increased towards the surface. One of them is probably localized near the surface; the other one (ΔEa=0.83 eV, σna=0.8×10−13 cm2) must be identified with the donor trap EL2; it is also present in the bulk, but with a lower concentration.