Defect characterization of Si-doped GaN films by a scanning near-field optical microscope-induced photoluminescence
Abstract
We developed a tapping-mode-scanning near-field optical microscope to measure near-field photoluminescence (SNOM-PL) with nanometer spatial resolution using an ultraviolet laser, and we measured the defect distribution of a Si-doped GaN film. The obtained result was compared with one measured by high spatial resolution cathodoluminescence (CL) spectroscopy. Some dark spots with an average period of 100-300nm were observed in the image of the peak intensity of near-field PL at about 362nm, measured with a pyramidical cantilever, and in a plan-view CL image at the same wavelength. The near-field PL image agreed well with the plan-view CL image. The threading dislocations in GaN films were found to act as nonradiative recombination centers not only for band-edge emission but also for yellow luminescence around 580nm. Furthermore, it was found that free carrier concentration decreased near the threading dislocations. The SNOM-PL we developed has at least a spatial resolution of about 100nm. The SNOM-PL could potentially be applied to the estimation at a nanometer scale of defects in semiconductor films without requiring a vacuum environment.
- Publication:
-
Applied Physics Letters
- Pub Date:
- April 2006
- DOI:
- 10.1063/1.2190270
- Bibcode:
- 2006ApPhL..88p1905Y
- Keywords:
-
- 68.55.Ln;
- 61.72.Ff;
- 61.72.Vv;
- 78.66.Fd;
- 78.55.Cr;
- 68.37.Uv;
- 78.60.Hk;
- Defects and impurities: doping implantation distribution concentration etc.;
- Direct observation of dislocations and other defects;
- Doping and impurity implantation in III-V and II-VI semiconductors;
- III-V semiconductors;
- III-V semiconductors;
- Near-field scanning microscopy and spectroscopy;
- Cathodoluminescence ionoluminescence