Electrical transport properties of Cu3Ge thin films

Abstract

Resistivity, Hall-effect, and magnetoresistance measurements have been performed in the temperature range 4.2-300 K on thin fihns of the er-Cu3Ge phase that has a long-range ordered monoclinic crystal structure. The results show that et-Cu3Ge is a metal with a room-temperature resistivity of -6 @ cm. The temperature dependence of resistivity follows the Block-Griineisen model with a Debye temperature of 240*25 K. The density of charge carriers, which are predominantly holes, is -8 X 10z2/cm3 and is independent of temperature and 8lm thickness. The Hall mobility at 4.2 K is -132 cm2/V s. The elastic mean free path is found to be -1200 A, which is surprisingly large for a metallic compound film. The results show that the residual resistivity is dominated by surface scattering rather than grain-boundary scattering. An increase in Ge concentration above 25 at. % (but less than 35 at. %) is found to affect the resistivity and Hall mobility, but not the density of charge carriers.

Compositional Study of Copper-Germanium Ohmic Contact to n-GaN

“…Based on these arguments, we suggest such a mechanism that would induce an n + interfacial region, narrowing the GaN depletion width and increasing the probability of electron tunneling from metal to semiconductor. Similar arguments were made for the Cu 3 Ge/GaAs system studied by Aboelfotoh et al 26 Ga and Ge diffusion across the metallurgical interface, which would support the proposed mechanism, was implied by the CuGa 2 phase detected by XRD. No complementary indication of Ge-N alloying is present, however, perhaps due to the 2h overlap of Ge 3 N 4 peaks with e 1 XRD peaks.…”

“…For the contact with excess Cu (10 at.% Ge), q c is slightly higher than for the fully reacted case, and if a greater effective interfacial area consists of Cu/GaN than f/GaN, q c would be greater than for the case of less Cu/GaN contact area, because Cu forms Schottky contact to n-GaN. 21 In previous work, 11 examination of the 30 at.% Ge film by Auger depth profiling showed 3:1 mixing of Cu to Ge after annealing, as well as interfacial diffusion of Cu, Ge, Ga, and N. Figure 6a shows that near the contact film/semiconductor interface, the concentration ratio of Cu to Ge drops below 3, suggesting that the cubic Ge detected by XRD for this film resides at this interface, and the remainder of 26 Fig. 6b suggests significant Ga diffusion into the contact film, which may form interfacial gallium vacancies V Ga , an energetically favorable defect in n-GaN.…”

Thermally stable Ge/Cu/Ti ohmic contacts to n-type GaN

“…31 Potential diffusion of small a amount of Ge into GaN may have also contributed to ohmic behavior because of predominantly donor behavior of amphoteric Ge in III-V compounds. 28 In addition, a high level of oxygen can be clearly seen at the surface of annealed samples (Figs. 2b-2d), which was not observed in the as-deposited sample (Fig.…”

“…The rationale for choosing 1:3 ratio was due to desired formation of e 1 -intermetallic Cu 3 Ge phase, which has advantages such as low temperature of formation, low electrical resistivity, high oxidation resistance, and high thermal stability. [28][29][30] …”

Thermal stability, mechanical and electrical properties of nanocrystalline Cu3Ge

“…At the lowest temperatures, the residual resistivity should become essentially independent of temperature. One of the previous authors has shown [38] that carriers in Cu 3 Ge are predominantly holes with a hole mean free path of 43 nm (40 nm for pure Cu). This value for the mean free path is comparable to or even larger than the average grain size, indicating that the grain boundaries do not significantly contribute to the residual resistivity.…”