Electric-Field-Enhanced Neutralization of Deep Centers in GaAs

The charge dynamics of hydrogenlike centers in semi-insulating GaAs have been studied by muon spin resonance in the presence of electric field and RF excitation. Electric-field-enhanced neutralization of deep electron and hole traps by track-induced hot carriers results in an increase of the excess electron’s or hole’s lifetimes. Similar processes may take place in semiconductor devices working at high voltages and/or under irradiation. As a consequence of the deep traps neutralization, the muonium (${\mu }^{+}+e^{-}$) center can capture a hole.

Figure 1

Typical experimental spectra (time-differential asymmetry) measured in semi-insulating GaAs after the electric field treatment measured at $T=70\mathrm{K}$ in longitudinal magnetic field $\mathrm{LF}=1837\mathrm{Oe}$ and zero electric field. Blue circles: RF signal is off; red triangles: RF signal is on.

Figure 2

Temperature dependencies of the diamagnetic RF asymmetry (amplitude of the oscillating contribution in Fig. 1) measured at zero electric field in different states of commercial SI-GaAs. Triangles: RF diamagnetic asymmetry in the virgin sample. Circles: enhanced RF signal in the treated sample. Stars: RF asymmetry measured in the process of the electric field treatment. All the data were measured on heating.

Figure 3

Experimental spectra (time-differential asymmetry) measured at $T=120\mathrm{K}$ in SI-GaAs after electric field treatment. Red circles: $E=+1\mathrm{kV}/\mathrm{cm}$. Blue triangles: $E=-1\mathrm{kV}/\mathrm{cm}$. Small negative electric fields reduce the precessing RF amplitude to the value measured for the virgin sample, while small positive electric fields have no effect on the amplitude.

Figure 4

Muon-nuclear level crossing integral spectra (integral asymmetry vs $H$) measured at $T=120\mathrm{K}$ in SI-GaAs in the treated state. Top panel: $E=+1.5\mathrm{kV}/\mathrm{cm}$. Bottom panel: $E=-1.5\mathrm{kV}/\mathrm{cm}$. Electric field is switched with $f=1\mathrm{kHz}$. The amplitude of the resonance at $\sim 1913\mathrm{Oe}$ does not depend on the direction of a small electric field. Different slopes reflect different ${\mathrm{Mu}}_T^0$ contributions. In negative field ${\mathrm{Mu}}_T^0$ is relaxing; in positive field ${\mathrm{Mu}}_T^0$ is converted to a diamagnetic signal.