High-Resolution X-ray Topography of Dislocations in 4H-SiC Epilayers
- PDF / 2,028,746 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 20 Downloads / 168 Views
0911-B05-11
High-Resolution X-ray Topography of Dislocations in 4H-SiC Epilayers Isaho Kamata1, Hidekazu Tsuchida1, William M Vetter2, and Michael Dudley2 1 Materials Science Research Laboratory, CRIEPI (Central Research Institute of Electric Power Industry), 2-6-1 Nagasaka, Yokosuka, Kanagawa, 240-0196, Japan 2 Department of Materials Science and Engineering, State University of New York, Stony Brook, New york, 11794-2275
ABSTRACT Synchrotron X-ray topography with high-resolution setup using 11-28 reflection was carried out on 4H-SiC epilayers. Four different shapes of threading edge dislocation (TED) images depending upon their Burgers vectors direction were observed. The four types of TED images were previously calculated by the computer simulation, and the experimental results correlated well with the simulation results. The detailed topographic features generated by plural screw dislocations and basal plane dislocations were also investigated.
INTRODUCTION SiC has excellent material properties such as superior breakdown electric field, high thermal conductivity and wide energy band gap. Thus, SiC devices are expected to be low-loss, high voltage and high temperature resistive devices. These days, some excellent performance of SiC devices has been reported [1]. While SiC substrates and epitaxial layers (epilayer) still contain many crystal defects, large devices have not shown good performance yet. Thus, it is important to understand precise properties of the crystal defects and dislocations, and to reduce the harmful defects and dislocations. Micropipes, screw dislocations, threading edge dislocations (TEDs) and basal plane dislocations (BPDs) are known as dislocations in SiC substrates and epilayers. They may affect device performance. The micropipes make lower reverse blocking voltages of devices [2]. The BPDs in an epilayer introduce stacking faults when bipolar devices operate in forward voltage bias (on-state) with forward current [3]. Therefore many dedicated efforts have been made to reduce the crystal defects from substrates and epilayers. Micropipes were drastically reduced in commercial wafers in this decade [4], and micropipes were closed in epitaxial layer during CVD growth by dissociation into several screw dislocations [5]. Recently, repeating aface (RAF) growth dramatically reduced the dislocations [6]. X-ray topography is a powerful tool to observe crystal defects and dislocations in SiC. It is a nondestructive evaluation method, and there is no difference in this observation for Si-face and C-face samples. Moreover, the X-ray topography gives us some depth information of dislocations in a sample. In a homo-epilayer grown on 4H-SiC wafer with an 8 degree surface off-cut, three types of dislocations are included: threading screw dislocations, TEDs, and BPDs propagating into an epitaxial layer at 8 degrees inclinations. These types showed different topographic images when the monochromatic synchrotron X-ray topography was taken by the grazing-incidence reflection
geometry using 11-28 reflecti
Data Loading...
