No abstract

A novel room-temperature inductively coupled plasma chemical vapour deposition (ICP–CVD) technique has been developed, which yielded high-quality silicon nitride (SiN) films with a hydrogen content of less than 3 at. %. The chemical composition and bonding of the films were analysed by energy dispersive X-ray (EDX) analysis, secondary ion mass spectrometry (SIMS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR). The film optical indexes measured by ellipsometry were well correlated with film composition. Very little plasma-induced damage was observed on Van de Pauw samples of GaAs-based high-electron-mobility transistor (HEMT) layer structures grown by molecular beam epitaxy (MBE). Breakdown electric field >4×106 V cm-1 was observed for an ultrathin 5 nm room-temperature-grown ICP–CVD SiN film embedded in a metal-insulator-metal (MIM) capacitor structure. This technique has been successfully incorporated into the III–V MMIC process flow to provide significant flexibility towards realising array-based MMICs.

GaN-on-diamond samples were demonstrated using a membrane-based technology. This was achieved by selective area Si substrate removal of areas of up to 1 cm × 1 cm from a GaN-on-Si wafer, followed by direct growth of a polycrystalline diamond using microwave plasma chemical vapor deposition on etch exposed N-polar AlN epitaxial nucleation layers. Atomic force microscopy and transmission electron microscopy were used to confirm the formation of high quality, void-free AlN/diamond interfaces. The bond between the III-nitride layers and the diamond was validated by strain measurements of the GaN buffer layer. Demonstration of this technology platform is an important step forward for the creation of next generation high power electronic devices.

. (2005) Index Terms-High-electron mobility transistor (HEMT), low noise, metamorphic, metamorphic high-electron mobility transistor (mHEMT), millimeter-wave imaging, nanometer gates, short gate.

Presented through this work is a steady state analytical model of the GaN HEMT based gas detector. GaN with high chemical and thermal stability provides promises for detectors in hazardous environments. However, HEMT sensor resolution must be improved to develop high precision gas sensors for automotive and space applications. The proposed model aids in systematical study of the sensor performance and prediction of sensitivities. The linear relation of threshold voltage shift at thermal equilibrium is used in predicting the sensor response. Numerical model for the reaction rates and the electrical dipole at the adsorption sites at the surface and metal/semiconductor interface have been developed and the sensor performance is analyzed for various gas concentrations. The validation of the model has been achieved through surface and interfacial charge adsorption-based gate electrode work function, Schottky barrier, 2DEG and threshold voltage deduction using MATLAB and SILVACO ATLAS TCAD. Further the applicability of gd (channel conductance) as gas sensing metric is also presented. With high ID and gd percentile sensitivities of 118.5% and 92 % for 10 ppm hydrogen concentration. The sensor shows capability for detection in sub-ppm levels by exhibiting a response of 0.043% for 0.01ppm (10 ppb) hydrogen concentration. The detection limit of the sensor (1% sensitivity) presented here is 169 ppb and the device current increases by 34.2 μA for 1ppb hydrogen concentration.