D. W. Murphy

Defect dominated charge transport in amorphous Ta2O5 thin films

Ta2O5 is a candidate for use in metal–oxide–metal (MOM) capacitors in several areas of silicon device technology. Understanding and controlling leakage current is critical for successful implementation of this material. We have studied thermal and photoconductive charge transport processes in Ta2O5 MOM capacitors fabricated by anodization, reactive sputtering, and chemical vapor deposition. We find that the results from each of these three methods are similar if one compares films that have the same thickness and electrodes. Two types of leakage current are identified: (a) a transient current that charges the bulk states of the films and (b) a steady state activated process involving electron transport via a defect band. The transient process involves either tunneling conductivity into states near the Fermi energy or ion motion. The steady state process, seen most commonly in films <300 A thick, is dominated by a large number of defects, ∼1019–1020 cm−3, located near the metal–oxide interfaces. The interi...

Passivation of GaAs using (Ga2O3)1−x(Gd2O3)x, 0⩽x⩽1.0 films

The Ga2O3(Gd2O3) dielectric film was previously discovered to passivate the GaAs surface effectively. We have investigated the systematic dependence of the dielectric properties of (Ga2O3)1−x(Gd2O3)x on the Gd (x) content. Our results show that pure Ga2O3 does not passivate GaAs. Films with x⩾14% are electrically insulating with low leakage current and high electrical breakdown strength. Furthermore, a low interfacial density of states was attained in films with x⩾14%. The results show the important role of Gd2O3 in the (Ga2O3)1−x(Gd2O3)x dielectric films for effective passivation of GaAs.

Passivation of GaAs using gallium-gadolinium oxides

The role of Gd2O3 is investigated in our previously discovered oxide films of Ga2O3(Gd2O3) for GaAs surface passivation. Based on the systematic dependence of the dielectric properties of (Ga2O3)1−x(Gd2O3)x on the Gd (x) content, we showed that pure gallium oxide does not effectively passivate GaAs, and Gd2O3 is a necessary component to stabilize the gallium oxide in the 3+ fully oxidized state due to the electropositive nature of Gd+3. This gives rise to electrically insulting films of low leakage current and high electrical breakdown strength.