열분해층을 이용한 자립형 GaN 기판의 HVPE 성장에 관한 연구

Abstract

Freestanding GaN (FS-GaN) substrate is inevitable for the high power and high speed optoelectronic devices. However, it is still difficult to obtain high quality large-area GaN substrate with low-cost. In this thesis, it is proposed to introduce a decomposable buffer layer (DBL) to fabricate the FS-GaN. Hydride vapor phase epitaxy (HVPE) is used to fabricate FS-GaN, and the growth condition for DBL and cap layer (CPL) were optimized to grow high quality thick GaN. The crystal quality of HT-GaN has been investigated in terms of optical, electrical and structural quality. This thesis consists of five chapters.

In chapter 1, the fundamental GaN properties, problems in the fabrication of FS-GaN substrate, and many application of the GaN are introduced. At the end of the chapter, the purpose of this study is addressed.

Chapter 2 describes the experimental and characteristic methods. HVPE was used as the growth method, field emission scanning electron microscopy (FE-SEM), high resolution x-ray diffraction (HR-XRD), micro Raman, cathodoluminescence (CL), photoluminescence (PL), Hall effect measurement were used as the characterization methods.

In chapter 3, DBL growth was optimized in terms of the thermal decomposition of GaN. Also, the chemical reaction mechanism and roles of DBL were described.

Chapter 4 describes on the design of growth and separation processes by using DBL. Also, the role of CPL was described. Moreover, investigate the feasibility of our proposal to fabricate the high quality FS-GaN substrate through the characterization of structural, optical and electrical properties of self-separated GaN.

Finally, the results found in this thesis are summarized and concluded in the chapter 5.