A new Z11 impedance technique to extract mobility andsheet carrier concentration in HFETs and MESFETs |
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Authors: | Ernst AN Somerville MH Del Alamo JA |
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Affiliation: | MIT, Cambridge, MA; |
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Abstract: | Conventional techniques to extract channel mobility, μ, and sheet carrier concentration, ns, in heterostructure field-effect transistors (HFETs) do not account for the distributed nature of the device. This can result in substantial errors. To address this, we have developed a new technique that consists of measuring the gate-to-source impedance with the drain floating (Z11) over a broad frequency range. A transmission line model (TL model) is fitted to ReZ11], thus obtaining the gate capacitance and channel resistance (and consequently μ(VGS) and ns(V GS)) in a single measurement. We demonstrate this technique in InAlAs-InGaAs on InP HFET's. The TL model faithfully represents Z11 from 100 Hz to 15 MHz. Our technique can easily be automated and thus is a good tool for accurate charge control in an industrial environment |
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