| Summary: | 博士 === 國立成功大學 === 微電子工程研究所碩博士班 === 94 === A newly developed liquid-phase oxidation technique, named liquid phase chemical-enhanced oxidation (LPCEO), for GaAs-based device applications has been proposed. The GaAs-based wafers are only immersed in a growth solution to form the oxidized film on the GaAs-based layer (e.g., AlGaAs, InGaAs, InAlAs, InGaP, and so on) at low temperature (from 30-70 oC) without any assisted energy source. Following the preliminary researches of the LPCEO-grown oxide films, the MOS-HEMTs with the LPCEO technique have been successfully demonstrated. The MOS-HEMT not only has the advantages of the MOS structure but also has the 2DEG channel.
The LPCEO-grown oxide film on AlGaAs is identified to mainly consist of mixtures of Ga2O3, As2O3, and Al2O3 by means of AES, XPS, and Raman spectroscopy. Moreover, the XPS signals of the Al-2p core level indicate that Al and Al oxides on the oxide surface are weak for long periods of oxidation time due to the strong pH-dependent solubility of Al2O3. In addition, the electrical properties of the oxide film have been measured by dc transport and capacitance techniques, and can be improved after rapid thermal annealing. The AlGaAs/InGaAs MOS-PHEMT has a larger gate voltage swing, a lower gate leakage current, a higher breakdown voltage, and an improved rf performance than those of the conventional PHEMT, making the proposed liquid phase oxidation suitable for high-power and high-speed applications.
The LPCEO-grown oxide film on InGaAs is identified to mainly consist of mixtures of Ga2O3, As2O3, and In2O3. On the other hand, the LPCEO-grown oxide film on InAlAs is identified to mainly consist of mixtures of As2O3, Al2O3, and In2O3. As compared to the conventional MHEMT, larger gate voltages, higher breakdown voltages, lower gate leakage currents with the suppressed impact ionization effect, and improved rf performance for the InAlAs/InGaAs MOS-MHEMT make the proposed liquid-phase oxidation suitable for device applications.
The LPCEO-grown oxide film on InGaP is identified to mainly consist of mixtures of Ga2O3 and InPO4. Although liquid phase oxidation on the InGaP material has a much slower oxidation rate of less than 10 nm/hr as compared to that of the GaAs material, it is still feasible to grow a thin oxide film. As compared to the counterpart of the conventional PHEMT, the proposed MOS-PHEMT can further reduce the gate leakage current, increase the breakdown voltage, and enhance the gate voltage swing. In addition, the pulse transient measurement shows a much lesser impact of the surface trap effects on the InGaP/InGaAs MOS-PHEMT owing to oxide passivation.
In other words, the investigation of the proposed low-cost, low-temperature LPCEO technique can provide a useful and potential method for GaAs-based electronic device applications.
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