Contactless measurements of rapidly thermal processed MBE GaAs on Si and GaAs wafers

Abstract

Contactless measurements of the optically injected excess carriers using a reflectance microwave probe (RMP) have been applied to characterize molecular beam epitaxy (MBE) GaAs on Si and Si + ion implanted semi-insulating (SI) liquid-encapsulated Czochralski (LEC) GaAs. The effective surface recombination velocity ( S eff) at the interface between the MBE GaAs layer and Si substrate is evaluated from the photoconductive decay curve using illumination with a laser diode (LD, λ = 904 nm) from the GaAs layer. The p-n junction of the n-GaAs/p-Si interface decreases the S eff as compared with that of the p-GaAs/p-Si interface which is comparable to that of Si substrate. The method to characterize the surface MBE GaAs layer with He-Ne laser (λ = 633 nm) pulse is also presented. The distribution of deep levels (EL2) in implanted SI GaAs wafer is measured by the signal intensity with LD pulse. The redistribution of deep level after Si + implantation and subsequent rapid thermal annealing is observed in undoped SI GaAs, but not in In- or Cr-doped ones. This is ascribed to the effect of locking of dislocations by impurities.