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Reduction in dislocation density and strain in GaN thin films grown via maskless pendeo-epitaxy

Roskowski A. M., Preble E. A., Einfeldt S., Miraglia P. M., Schuck J., Grober R., Davis R. F.

Opto-Electronics Review

2002

Vol. 10, No. 4

262-270

Maskless pendeo-epitaxy (PE) involves the lateral and, commonly, the vertical growth of cantilevered “wings” of material from the side-walls of unmasked etched forms. Cross-sectional SEM micrographs revealed that films grown at 1020 C exhibited similar vertical [0001] and lateral [1120] growth rates. Increasing the temperature increased the latter due to the higher thermal stability of the GaN(1120). The (1120) surface was atomically smooth under all growth conditions with an RMS = 0.17 nm. High resolution X-ray diffraction (HRXRD) and atomic force microscopy of the PE films confirmed transmission electron microscopy results regarding the reduction in dislocation density in the wings. Measurement of strain indicated that the wing material is crystallographically relaxed as evidenced by the increase in the c-axis lattice parameter and the upward shift of the E2 Raman line frequency. However, tilting of the wings of ≤ 0.15 occurred due to the tensile stresses in the stripes induced by the mismatch in the coefficients of thermal expansion between the GaN and the underlying substrate.

Deposition and properties of refractory metallic films for diffusion barrier applications in Au-based metallizations to III-V semiconductors

Kamińska E., Piotrowska A., Guziewicz M., Gołaszewska K., Barcz A., Turos A., Mizera E., Adamczewska J., Rouvimov S., Liliental-Weber Z., Bremser M. D., Davis R. F.

Electron Technology

1999

Vol. 32, No. 4

304-326

We present a comprehensive investigation of titanium, tungsten and zirconium nitrides and borides as diffusion barriers in Au-based ohmic contracts to III-V semiconuctors, including GaAs, InP, GaSb and GaN. Thin films of refractory metallic compounds were deposited using sputtering methods. The resistivity and mechanical properties of these films were optimized by adjusting the deposition parameters such as power, substrate bias and gas pressure. Characterization of barrier layers included determination of thier microstructure and chemical reactivity towards III-V semiconductors. Complete metallization, with Au(Zn) ohmic contact metallization and Au overlayer has ben used as a model in the study of the effectiveness of barrier layers.