| Summary: | 碩士 === 國立成功大學 === 微電子工程研究所碩博士班 === 93 === Liquid phase oxidation (LPO) method to grow native oxide films on InGaP/GaAs HBTs near room temperature is investigated and characterized. This is a very simple, low-cost and low-temperature (30-70oC) technique to grow uniform and smooth native oxide films. In the liquid phase oxidation system, neither anodic equipment nor assisting energy source is needed. Additionally, scanning electron microscopy (SEM) and atomic force microscopy (AFM) are used to analyze the surfaces of the grown oxide films. Moreover, from the chemical analysis of x-ray photoelectron spectroscopy (XPS) and auger electron spectroscopy (AES), the oxide films are found to be a composite of the Ga2O3 and As2O3. Since the passivation on the GaAs surface is one of the key issues in III-V materials to reduce the density of surface states, leading to the reduction of the surface recombination velocity and improvement of the device performance, therefore, the implementation of LPO as the surface passivation to improve the InGaP/GaAs heterojunction bipolar transistors (HBTs) performance is also demonstrated. In this work, the current gain of the HBT devices with a native oxide film as the surface passivation increase 7 fold in low collector current regimes. In addition, a larger reverse-bias base-collector breakdown voltage, 23.5 V, and a lower base recombination current, 2×10-12 A, are also obtained.
Furthermore, sulfur solutions are used to compare with the LPO method. It was found that the device with an oxide passivation exhibits the highest breakdown voltage. Additionally, the device with a surface passivation shows wider collector regimes from 8.3×10-11 A to 0.1 A. Moreover, an order of magnitude improve in the current gain from the collector current of 8.1×10-10 A to 8.3×10-11 A. This gives promising implementations to low-power electronics and communication applications.
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