• PDF / 2,587,435 Bytes
• 6 Pages / 612 x 792 pts (letter) Page_size
• 90 Downloads / 176 Views

DOWNLOAD

REPORT

---

1246-B03-02

Non-destructive detection and visualization of extended defects in 4H-SiC epilayers Gan Feng1, Jun Suda1, and Tsunenobu Kimoto1,2 1 2

Department of Electronic Science and Engineering, Kyoto University, Japan Photonics and Electronics Science and Engineering Center, Kyoto University, Japan

ABSTRACT The extended defects, such as dislocations and in-grown stacking faults (IGSFs), in 4H-SiC epilayers have been detected and visualized by a non-destructive method, the micro photoluminescence (µ-PL) intensity mapping method, at room temperature. The one-to-one correspondence between the extended defects and the µ-PL mapping contrast has been successfully obtained. A threading dislocation corresponds to a dark circle with the reduced intensity in the µ-PL mapping image performed at 390 nm, while a basal plane dislocation dissociates into a single Shockley SF during the measurements. Three kinds of IGSFs have been identified in the samples. Each kind of IGSF shows the distinct PL emission located at 460 nm, 480 nm, and 500 nm, respectively. The shapes and distributions of IGSFs have also been profiled by µ-PL intensity mapping. INTRODUCTION SiC is a wide band gap semiconductor with promising applications in high-power, hightemperature, and high-frequency devices, owing to its superior properties [1].One limitation to the commercialization of 4H-SiC power devices is the occurrence of extended defects in the epitaxial layers and their adverse effects on devices. The further market penetration of SiC devices will in a large part depend on the continued reduction of these extended defects and improved techniques for identifying them. To address these issues, it is crucial to develop or upgrade techniques for precisely visualizing these extended defects, especially the non-surface morphological defects, such as dislocations and in-grown stacking faults (IGSFs). Several techniques were developed to detect and image the extended defects in 4H-SiC epilayers, such as molten KOH etching and X-ray topography [2,3]. This work highlights the optical method, micro photoluminescence (µ-PL) mapping, to detect and visualize the various types of dislocations and IGSFs in 4H-SiC epilayers. The µ-PL mapping technique has a number of advantages compared to other methods for examining dislocations and in-grown SFs. It is non-destructive and the whole-wafer scan makes it an attractive method to characterize wafers before fabrication [4]. µPL mapping is also better than other techniques for the selective visualization of the given extended defects in the whole wafer. EXPERIMENTAL DETAILS 4H-SiC epilayers were grown on 8o off-axis 4H-SiC (0001) n+ substrates (doping concentration: 5-6x1018 cm-3) by horizontal hot-wall chemical vapor deposition in a SiH4-C3H8H2 system [5]. Epitaxial growth was performed at 1650 oC with a reactor pressure of 30 Torr and

the C/Si ratio of 1.2. The growth rate was 60-90 µm/h. The epilayers were intentionally doped with nitrogen donors to 1.0x1015 cm-3. µ-PL spectroscopy and µ-PL intensity mapping were p