Electrostatic Tuning of Charge Transfer Mechanisms for Enhanced Gas Detection with Nanowire FETs

Indium-arsenide (InAs) nanowire field-effect transistors (NWFETs) combine high electron mobility with extreme surface sensitivity, making them promising platforms for biochemical agent detection at room temperature. Yet understanding the relative roles of electrostatic screening, impurity scattering, and molecular charge transfer in governing their response remains incomplete. Here, we couple time-resolved measurements of multi- nanowire InAs FETs exposed to dimethyl methylphosphonate (DMMP) vapor (50-200 ppb) with a self-consistent charge-neutrality solver that incorporates Kane-model sub-band structure and Brooks-Herring ionized-impurity scattering. We uncover a gate-tunable "electrostatic sweet spot'' in which depletion of the one-dimensional carrier gas both perturbs the overall charge landscape and lengthens the Debye screening length to the nanowire diameter, yielding a six-fold gain in sensitivity and a limit of detection of 50 ppb. In this regime, quantitative fitting shows that ≈75 electrons are withdrawn from the channel per ppm of DMMP where an 80% reduction of the baseline carrier pool that drives the nonlinear response exists. The model accurately reproduces the measured gain, resolves the separate contributions of charge transfer and scattering, and maps how geometry (radius, oxide thickness), bias, and temperature steer sensor performance. Because the framework depends only on material-specific band and trap parameters, it can be ported directly to other semiconductor/molecule combinations-e.g., Si or metal-oxide nanowires sensing volatile organic compounds-providing a predictive pathway for rational design of low-power, high-dynamic-range chemical sensors for environmental monitoring and industrial safety applications.