| Research Abstract |
In order to improve the surface electronic properties of GaAs, we have developed a new surface chemical treatment with the (NH_4)_2S_x solution (or(NH_4)_2S_x treatment). Especially, we studied on the treatment effects in chemical, physical, and electronic scopes. Furthermore, we extended the effect to III-V compound semiconductors.
We first investigated the electrical characteristics of Schottky structure and found the Schottky barrier height becomes metal-dependent after the (NH_4)_2S_x treatment. Also studied were the C-V characteristics of MIS structure and we found that the frequency dispersion is reduced by the treatment. All these results on the Schottky characteristics, MIS C-V characteristics, and MIS DLTS measurements consistently indicate that surface state density of GaAs is significantly reduced by the (NH_4)_2S_x treatment.
Next, we investigated the surface structure by using various analysis techniques such as AES,LEELS,SRPES,CAICISS,RHEED,STM and XSW.Based on those experimental observations, we proposed a model to explain the mechanism of successful (NH_4)_2S_x treatment. The model neatly explains all the results including a generation mechanism of surface defect which was detected by SPB technique.
As a result, we concluded that (1) replacement of V atoms by sulfur at the surface first layr plays an important role in surface stabilization, and (2) both effect and structure on the (NH_4)_2S_x-treated surface are almost universal to III-V compound semiconductors in general.
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