Wenxin Wang

A High Performance In0.7Ga0.3As MOSFET with an InP Barrier Layer for Radio-Frequency Application

We demonstrate a high performance implant-free n-type In0.7Ga0.3As channel MOSFET with a 4-nm InP barrier layer fabricated on a semi-insulating substrate employing a 10-nm Al2O3 as gate dielectric. The maximum effective channel mobility is 1862 cm(2)/V.s extracted by the split C V method. Devices with 0.8 mu m gate length exhibit a peak extrinsic transconductance of 85mS/mm and a drive current of more than 200mA/mm. A short-circuit current gain cutoff frequency f(T) of 24.5 GHz and a maximum oscillation frequency f(max) of 54 GHz are achieved for the 0.8 mu m gate-length device. The research is helpful to obtain higher performance In0.7Ga0.3As MOSFETs for radio-frequency applications.

Effects of indium doping on the properties of AlAs/GaAs quantum wells and inverted AlGaAs/GaAs two-dimensional electron gas

The effects of indium doping on the optical properties of AlAs/GaAs quantum wells (QWs) and the electrical properties of inverted AlGaAs/GaAs two-dimensional electron gas (2DEG) were investigated. It is found that incorporation of a small amount of In in AlAs layers can decrease the photoluminescence linewidths of AlAs/GaAs QWs drastically and a small amount of In doping in AlGaAs layers can increase significantly the electron mobilities of inverted AlGaAs/GaAs 2DEG at 77 K. All these results demonstrate that In doping can improve the interface roughness because In as a surfactant can enhance the surface migration of Al adatoms during molecular beam epitaxy.

The study of thermal stability during wet oxidation of AlAs

A structure in which a 1000 Angstrom thick AlAs layer is sandwiched between 1000 Angstrom thick GaAs cap layer and 2000 A GaAs buffer layer was subsequently grown by molecular beam epitaxy on the GaAs substrate. The AlAs layer was laterally oxidized in N-2 bubbled H2O vapor ambient at 400 degreesC for 20, 30, 40, 60, and 120 min. It was found that the thermal stability of the mesas is very dependent on the removal rate of volatile products, such as As and As2O3. The removal of volatile products is dependent on the oxidation time and temperature. The Raman spectra presented here proved that the spectra were different from samples, oxidized for different time durations

Direct Observation of Carrier Transportation Process in InGaAs/GaAs Multiple Quantum Wells Used for Solar Cells and Photodetectors*

The resonant excitation is used to generate photo-excited carriers in quantum wells to observe the process of the carriers transportation by comparing the photoluminescence results between quantum wells with and without a p—n junction. It is observed directly in experiment that most of the photo-excited carriers in quantum wells with a p—n junction escape from quantum wells and form photocurrent rather than relax to the ground state of the quantum wells. The photo absorption coefficient of multiple quantum wells is also enhanced by a p—n junction. The results pave a novel way for solar cells and photodetectors making use of low-dimensional structure.