InGaAs Quantum-Well MOSFET Arrays for Nanometer-Scale Ohmic Contact Characterization

We demonstrate InGaAs quantum-well (QW) MOSFET arrays with Mo contact lengths between 40 and 800 nm fabricated by a self-aligned process. A gate pitch of 150 nm is realized, which is the smallest at present for any type of InGaAs FET structure. Fabricated gated MOSFET arrays and gate-less arrays are used to study the properties of nanoscale ohmic contacts in InGaAs MOSFETs with different contact lengths. A three-layer resistive-network model is developed to analyze the contact electrical characteristics. From this paper, we extract a contact resistivity from Mo to n + InGaAs of 8 $\times 10^{\mathrm {-9}}~\Omega \cdot {\mathrm{ cm}}^{2}$ , and from n + InGaAs to the QW channel of $2\times 10^{\mathrm {-8}}~\Omega \cdot \text {cm}^{2}$ . When benchmarked with other ohmic contact technologies for n-type InGaAs MOSFETs, our refractory metal contact approach represents the lowest film resistivity and is among the lowest contact resistivity that has been demonstrated. The contact model developed here infers a contact resistance from the Mo contact to the channel of 260 $\Omega \cdot \mu \text{m}$ for a contact length of $L_{c}=10$ nm. This suggests that further research on low-resistance ohmic contacts is required before InGaAs MOSFETs can deliver the required performance.