Fabrication of PtGe/Ge contacts with high on/off ratio and its application to metal source/drain Ge p-channel MOSFETs

Abstract

We study the level spacing distribution p(s) in the spectrum of random networks. According to our numerical results, the shape of p(s) in the Erdős-Rényi (E-R) random graph is determined by the average degree k and p(s) undergoes a dramatic change when k is varied around the critical point of the percolation transition, k = 1. When k 1, the p(s) is described by the statistics of the Gaussian orthogonal ensemble (GOE), one of the major statistical ensembles in Random Matrix Theory, whereas at k = 1 it follows the Poisson level spacing distribution. Closely above the critical point, p(s) can be described in terms of an intermediate distribution between Poisson and the GOE, the Brodydistribution. Furthermore, below the critical point p(s) can be given with the help of the regularized Gamma-function. Motivated by these results, we analyse the behaviour of p(s) in real networks such as the internet, a word association network and a protein-protein interaction network as well. When the giant component of these networks is destroyed in a node deletion process simulating the networks subjected to intentional attack, their level spacing distribution undergoes a similar transition to that of the E-R graph.

Effects of metal/Ge contact and surface passivation on direct band gap light emission and detection for asymmetric metal/Ge/metal diodes

“…Note that Φ BN could be obtained from the forward I-V characteristics for PtGe=Ge and HfGe=Ge contacts 22) (data not shown here), which are 0.55 (HfGe-ECR), 0.57 (HfGe-BLP), 0.59 (PtGe-ECR), and 0.60 eV (PtGe-BLP). Here, Φ BN (0.60 eV) for the PtGe=Ge contact of PtGe-BLP is lower than those for other PtGe=Ge contacts fabricated in our previous work by a similar process (Φ BN = 0.64 eV), 29) which should be associated with the long perimeter of the fintype electrode. Generally, the reverse current intensity I R is given by I R = AJ A + PJ P , where A is the contact area, P is the contact perimeter, and J A (A=cm 2 ) and J P (A=cm) are the areal and peripheral current densities, respectively.…”

“…During the above process, PtGe=Ge and HfGe=Ge contacts were automatically formed owing to the germanide formation. 4,28,29,31) The thickness of the HfGe layer was at least 10 nm before PMA, which was confirmed by cross-sectional transmission electron microscopy and energy-dispersive Xray spectroscopy. This thickness should increase after PMA.…”

“…The electrical properties of PtGe=Ge and HfGe= Ge were confirmed to be stable at temperatures below 500 °C. 29,32) After the formation of PtGe=Ge and HfGe=Ge contacts, TiN (right side metal) was also deposited by radio frequency (rf) magnetron sputtering and patterned by a liftoff process, followed by PMA in N 2 at 350 °C for 30 min. The surface of the active region was passivated using two methods.…”

“…To resolve this issue, PtGe=Ge contact (Φ BN = 0.60-0.64 eV) 27,28) is proposed to replace HfGe=Ge contact because a crystalline PtGe layer can be formed at a temperature of around 400 °C without the oxidation problem. 29) Besides the issue of parasitic resistance of metal=Ge contact, the surface passivation of the active region is also important. In our previous work, an electron cyclotron resonance (ECR) plasma oxidation method was used for this passivatinon.…”

Fabrication and characterization of asymmetric metal/Ge/metal diodes with Ge-on-insulator substrate

“…20,21) Then the performance was enhanced by optimizing the asymmetric MGM diodes. For example, we replaced the HfGe contact with PtGe, because PtGe has lower parasitic resistivity 22,23) and higher Φ BN (0.60-0.64 eV), 24,25) implying high efficient hole injection and low leakage-current density. We also improved the surface quality of the active region by employing a physical vapor deposition (PVD) SiO 2 /GeO 2 bilayer passivation (BLP) method.…”