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A comparison of deep levels in rapidly thermal-processed GaAs films grown by molecular beam epitaxy on Si and GaAs substrates

A comparative study of the rapidly thermal-processed molecular beam epitaxial GaAs grown on Si and GaAs substrates is made by deep-level transient spectroscopy (DLTS). Rapid thermal processing (RTP) was performed at 910 degrees C for 9 s with SiO2 encapsulation. In the MBE layer on Si, the traps A1 (Ec-0.65 eV) and A2 (Ec-0.81 eV) are observed in addition to the trap M1 (Ec-0.18 eV) and M4 (Ec-0.51 eV) which are also commonly present in the MBE layer on GaAs. Two traps are produced by RTP in the layer on GaAs, and one of them is identified with EL2 (Ec-0.81 eV) and another one with the activation energy of 0.49 eV is labelled NC2. On the other hand, four electron traps termed R1 (Ec-0.23 eV), R2 (Ec-0.40 eV), R3 (Ec-0.44 eV) and EL2h (Ec-0.79 eV) are produced by RTP in the layer on Si. The trap EL2h is one of an EL2 family characterised by the persistent photocapacitance quenching effect. The EL2h concentration is consistent with the EL2 concentration produced by RTP in the surface region (<0.2 mu m below the surface), but in the deeper position the EL2h concentration is different from the EL2 concentration in the MBE layer on GaAs after RTP. It is suggested that the EL2h profile produced by RTP depends on the distribution and intensity of stress in the heteroepitaxial layer.