Attempts to correlate hydrogen plasma-induced and Si 3N 4/GaAs interface-related surface states: a charge deep-level transient spectroscopy study

Abstract

Heavily doped (100) GaAs:Si substrates were exposed for up to 32 min to H 2 + Ar discharges while keeping the substrates at 300°C. Both direct and remote mode plasma exposures were conducted with the aim of comparing the respective plasma-induced damages. After the remote hydrogen plasma treatment, not only the amount of charge released from plasma-induced deep levels in Al/GaAs diodes in the course of a DLTS scan had been reduced, moreover, the zero-bias crossover E FT of the Fermi level and the trap level could be shifted up to E C − E FT ≈ 0.01 eV. The latter shift was not connected with any changes of the Al/GaAs barrier height which was found to be essentially insensitive to the plasma treatment ( φ B ≈ 0.8 eV). Nevertheless, the distributed damage-related energy levels of all processed substrates could be characterized by a unique dependence of the capture cross-section σ on the activation enthalpy ΔE of the corresponding charge deep-level transient spectroscopy (DLTS) peaks as σ = σ 0 exp( ΔE E 0 ) , E 0 being a constant. Finally, we constructed an equivalent ln σ versus ΔE plot for charge DLTS data of Al/Si 3N 4/GaAs metal-insulator-semiconductor (MIS) structures with silicon nitride layers prepared in the same reactor at comparable temperatures, and included it in the Al/GaAs-related data. The combined data provided a single plot that exhibits two perfectly jointed branches differing in respective slopes. As expected, shallow Si-donor passivation could be detected too, the efficiency of the latter reaching 90% under the direct mode hydrogen plasma conditions.