Pd-Ge contact to n-GaAs with the TiW diffusion barrier

Comparison of Ti/Pd/Ag, Pd/Ti/Pd/Ag and Pd/Ge/Ti/Pd/Ag contacts to n-type GaAs for electronic devices handling high current densities

“…When it comes to minimizing the specific metal-semiconductor contact resistance, another interesting metallization system that has been widely studied lately is that based on Pd/Ge, which has been reported to show very low metalsemiconductor specific contact resistance (∼10 −7 -10 −6 Ω cm 2 ) [21][22][23][24][25][26]. Since Pd/Ge-based contacts show no spiking and have smooth surfaces comparable to unalloyed contacts [24][25][26], they can be combined with diffusion barriers such as TiPt [27] or W [28], with a highly conductive metal on top to increase its bondability and sheet conductivity.…”

Structure and stability studies on W, WSi, WSiN/GaAs systems by XRD

“…The high-temperature and long-term stability of Schottky contacts on GaAs or related III-V semiconductors have been studied intensely during recent years. The refractory metal tungsten and a variety of W alloys and compounds have been objects of particular study [1][2][3][4][5][6]. These materials are also of importance for the self-aligned refractory gate techniques used for the fabrication of MESFETs and HEMTs.…”

Application of advanced thin film technologies to the manufacture of multijunction solar cells

“…Given the fact that even small impurity concentrations tend to affect the conductivity of thin films, it seems plausible that the Ag layer is not contaminated by GaAs, supporting the idea that TiPd works fine as a barrier layer, hindering the diffusion of Ga and As atoms into Ag layer. Of course this result is not an unequivocal proof for lack of significant diffusion though it is certainly in line with the results with Ti/Pd/Au reported by Chor et al [29] and Jones et al [30], where no significant contamination of the Au layer could be measured for RTA processing temperatures of 500ºC or less. On the contrary, the metal resistivity of AuGe/Ni/Au system is one order of magnitude lower than that of pure bulk gold.…”

“…Moreover, if excess Ge is present, a thin epitaxial Ge layer also grows on top of the n++GaAs, forming a GeGaAs heterojunction that further contributes to the lowering of the metalsemiconductor barrier height [25][26][27]. Since all these reactions take place in a quasiplanar front, PdGe-based contacts show no spiking and smooth surfaces comparable to unalloyed contacts [25][26][27] and can be combined with diffusion barriers such as TiPt [28] or W [29] to increase its bondability and sheet conductivity.…”

“…In fact, pursuing some of these ideas, there are some works in the literature reporting the use of Ti/Pd/Au on p-GaAs [29], and other Ti-based contacts on GaAs, such as Chapter 4 Development of new metallizations on n-type GaAs for high current density devices Despite its potential advantages, a thorough study of Ti/Pd/Ag metallization characteristics on n-GaAs is lacking, and would offer a more cost-effective alternative than systems using Pt and Au. Accordingly, in this section we present an assessment of Ti/Pd/Ag contacts to n-GaAs as a function of the n-GaAs doping level and contact annealing treatment; analyzing the impact of these variables on the Schottky/Ohmic nature of the contact; its specific contact resistance and the influence of contact formation on the metal resistivity and morphology (i.e.…”