Optimization of ZnO:Ga properties for application as a transparent conducting oxide in InGaN based light emitting diodes
2011
We report on the effects of substrate temperature and surface morphology of p-GaN templates on the
properties of ZnO:Ga (GZO) layers grown by plasma-assisted molecular beam epitaxy. Substrate temperature varying
from 200 °C to 450°C was found to have only a moderate effect on the electrical properties of GZO films but it greatly
affects the surface morphology of the GZO films. The surface morphology and growth mode of GZO were also found to
be considerably affected by the surface morphology of underlying p-GaN templates. On p-GaN templates with a smooth
surface (RMS = 0.4 nm) featured by clear atomic steps, GZO layers grew in 2D growth mode and exhibited smooth
surfaces with RMS roughness of 2 nm. In contrast, on p-GaN without clear atomic steps but having comparable surface
roughness of 0.6 nm, GZO layers grew in 3D growth mode and exhibited rough surface (RMS roughness of ~17.0-20.0
nm). The results of surface roughness are consistent with those from TEM measurements. The lowest resistivity of
~2.3×10 -4 Ω·cm for as-grown GZO layers has been achieved at substrate temperature of 350°C, while the data for 2D
GZO layers was affected by a parallel conduction channel from underneath GaN and require further studies. Although
the differences in electrical properties and surface morphology existed, the GZO layers grown on different p-GaN
templates showed optical transparency higher than 90% in the visible spectral range. The performance of 3D GZO layers
as p-electrode was tested in InGaN light emitting diodes.
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
0
References
2
Citations
NaN
KQI