Joyce Pei Ying Tan

AlGaN/GaN two-dimensional-electron gas heterostructures on 200 mm diameter Si(111)

This Letter reports on the epitaxial growth, characterization, and device characteristics of crack-free AlGaN/GaN heterostructures on a 200 mm diameter Si(111) substrate. The total nitride stack thickness of the sample grown by the metal-organic chemical vapor deposition technique is about 3.3 ± 0.1 μm. The structural and optical properties of these layers are studied by cross-sectional scanning transmission electron microscopy, high-resolution x-ray diffraction, photoluminescence, and micro-Raman spectroscopy techniques. The top AlGaN/GaN heterointerfaces reveal the formation of a two-dimensional electron gas with average Hall mobility values in the range of 1800 to 1900 cm2/Vs across such 200 mm diameter GaN on Si(111) samples. The fabricated 1.5 μm-gate AlGaN/GaN high-electron-mobility transistors exhibited the drain current density of 660 mA/mm and extrinsic transconductance of 210 mS/mm. These experimental results show immense potential of 200-mm diameter GaN-on-silicon technology for electronic devi...

Direct Current and Microwave Characteristics of Sub-micron AlGaN/GaN High-Electron-Mobility Transistors on 8-Inch Si(111) Substrate

We report for the first time the DC and microwave characteristics of sub-micron gate (~0.3 µm) AlGaN/GaN high-electron-mobility transistors (HEMTs) on 8-in. diameter Si(111) substrate. The fabricated sub-micron gate devices on crack-free AlGaN/GaN HEMT structures exhibited good pin.-off characteristics with a maximum drain current density of 853 mA/mm and a maximum extrinsic transconductance of 180 mS/mm. The device exhibited unit current-gain cut-off frequency of 28 GHz, maximum oscillation frequency of 64 GHz and OFF-state breakdown voltage of 60 V. This work demonstrates the feasibility of achieving good performance AlGaN/GaN HEMTs on 8-in. diameter Si(111) for low-cost high-frequency and high-power switching applications.

Kinetically constraint zero-and one-dimensional heteroepitaxial island growth

Direct observation of the dynamics, formation, and selective growth of low dimensional epitaxial Fe13Ge8 structures [zero-dimensional (0D) compact islands or one-dimensional (1D) wires of different aspect ratios] was conducted in real time using in situ ultra high vacuum transmission electron microscopy at 350, 430, 480, and 510°C. Both types of island (0D/1D) share the same epitaxial relation to the underlying Ge substrate. The compact islands are formed preferentially at lower deposition temperature while wires, which are kinetically constrained, at higher temperature. The effective Ea for growth along two orthogonal azimuths of an Fe13Ge8 island are 0.17 and 0.95eV. The temperature dependence in morphological evolution is due to anisotropy in corner barriers and ledge diffusion on orthogonal azimuths during growth.

Improved OFF-state breakdown voltage in AlGaN/GaN HEMTs grown on 150-mm diameter silicon-on-insulator (SOI) substrate

The AlGaN/GaN-based high-electron-mobility transistors (HEMTs) are suitable for discrete components in many high power and high frequency power electronics applications useful for communications, satellites, power amplifiers, inverters/converters for electric and/or hybrid vehicles. Presently, these devices are commonly grown on sapphire, silicon carbide, and recently on 100- to 200-mm diameter silicon substrates. For a large scale deployment of low cost GaN-based power electronic devices, silicon substrate offers tremendous opportunities due to mature back-end Si process technologies. However, GaN epilayers on large area Si substrates results in severe wafer bowing and cracking due to high thermal mismatch between nitride layer and the substrate. As an alternative to Si substrate, silicon-on-insulator (SOI) substrate has been used for the demonstration of GaN-based light emitting diodes (LEDs)[1]. To the best of our knowledge, the demonstration of AlGaN/GaN transistors on a thin SOI substrate is rather limited. In this study, we report on the growth and characteristics of AlGaN/GaN heterostructures (HSs) on 150-mm diameter Si(111) and SOI(111) substrates. In addition, fabrication of HEMTs and device characteristics will be discussed on the SOI platfrom.