RESUMO
The effect of Mg doping on the electrical and optical properties of the p-GaN/AlGaN structures on a Si substrate grown by metal organic chemical vapor deposition was investigated. The Hall measurement showed that the activation efficiency of the sample with a 450 sccm Cp2Mg flow rate reached a maximum value of 2.22%. No reversion of the hole concentration was observed due to the existence of stress in the designed sample structures. This is attributed to the higher Mg-to-Ga incorporation rate resulting from the restriction of self-compensation under compressive strain. In addition, by using an AlN interlayer (IL) at the interface of p-GaN/AlGaN, the activation rate can be further improved after the doping concentration reaches saturation, and the diffusion of Mg atoms can also be effectively suppressed. A high hole concentration of about 1.3 × 1018 cm-3 can be achieved in the p-GaN/AlN-IL/AlGaN structure.
RESUMO
The biodegradable polylactide/poly(ethylene glycol) (PLA/PEG) hybrid membranes were fabricated via electrospinning of PLA/PEG solution. Their structures and properties were investigated by scanning electron microscopy, differential scanning calorimetry, and water contact angle. In vitro hydrolytic degradation showed that PEG content influenced the degradation rate of the PLA/PEG hybrid mats. The mechanical property was measured by tensile test and the result revealed that the addition of PEG had an obvious plasticization on PLA matrix. In-vitro biocompatibility was investigated by culturing cell on the scaffolds and MTT assay. The results indicated that the cell could attach and proliferate on the membranes, so confirmed that the PLA/PEG hybrid membrane had good biocompatibility, and it could be a promising biomaterial for tissue engineering applications.
