A study on the electrical properties of GaAs channel devices with atomic-layer-deposited Al2O3 gate dielectric

• Main Authors: He, Tsung-Lin, 何宗霖
• Other Authors: Chien, Chao-Hsin
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/54412949710533894166

碩士 === 國立交通大學 === 電子研究所 === 99 === In this thesis, we demonstrated that the Fermi level (EF) of GaAs on the surface could be adjusted to the level of the inversion mode via optimizing the surface treatment. With the optimized treatment, the interface state density (Dit) in the middle of energy bandgap of GaAs could be significantly eliminated to a value of 2E12cm-2V-1. At first, we studied the electrical characteristics on GaAs MOS capacitor with Al2O3 gate dielectric formed by atomic-layer-deposition (ALD). We not only utilized Berglund’s integration to obtain the relation between surface potential and gate voltage but also compared the Dit distribution within energy bandgap by the different extraction methods. Next, we studied the reduction of native oxides on GaAs substrates by trimethylaluminum (TMA) pretreatment before ALD of Al2O3 and examined the impact of the electrical characteristics on GaAs MOS capacitors. Although we did not observe anything different on electrical characteristics and XPS analysis, we found the improvement in the value of k and effective oxide thickness after calculation with the TEM image. Then, we studied the electrical characteristics on GaAs MOS capacitors with the different surface orientation of substrates. There was improvement on GaAs MOS capacitors with (111)A surface orientation. The EF of surface on GaAs could reach inversion region and the value of Dit in the middle of energy bandgap was decreased. We presumed that improvement was caused by the different structure of surface on substrate. Finally, we fabricated E-mode GaAs n-MOSFET on semi-insulator substrate. The electronic mobility we extracted was 15 cm2V-1S-1 and the on/off ratio was 4.12E3; the lower mobility and poor on/off ratio were due to the unsuccessful S/D activation. In addition, we also fabricated InGaAs channel MESFET with Ge S/D and studied electrical characteristics.