Doctor of Philosophy / Department of Physics / Hongxing Jiang / The correlation between polarity and material quality of un-doped Al[0.81subscript]Ga[0.19subscript]N was
studied. The overall material quality is significantly influenced by the growth polarity. The
epilayers with aluminum-polarity have a much higher crystalline quality and better surface
morphology than those of nitrogen-polarity. Nitrogen-polar growth more readily incorporates
unintentional impurities.
A-plane AlN epilayers have been grown on r-plane sapphire substrates. The orientation
and high crystalline quality were confirmed by x-ray diffraction (XRD) [Theta]-2[Theta] scan exhibiting a
reflection peak at 2[Theta] = 59.4[0superscript] and rocking curve of the (110) reflection having a line width of 940
arcsec. Room temperature photoluminescence (PL) spectroscopy showed that the surface
emission intensity of a-plane AlN epilayers is comparable to that of c-plane AlN. PL spectra of
Mg-doped a- and c-plane AlN revealed that the Mg level in both a- and c-plane AlN is identical
and is about ~ 0.5 eV.
Identically designed a-plane and c-plane AlN/A1[0.65subscript]Ga[0.35subscript]N QWs have been grown on a-and
c-plane AlN/Al[2subscript]O[3subscript] templates respectively, and their PL emission properties were studied.
Low temperature PL characteristics of a-plane QWs are primarily governed by the quantum size
effect, whereas those of c-plane QWs are significantly affected by the polarization fields.
The growth of AlN epilayers on SiC substrates was investigated. A smooth, crack free
AlN epilayer with high optical and crystalline quality was achieved. Because of its high quality,
AlN was used as active layer in a hybrid Schottky photodetector.
Highly conductive Si-doped Al[subscript0.75]Ga[0.25subscript]N alloys were grown on AlN/SiC templates. The
effects of using Indium as a surfactant during the growth of Si-doped Al[0.75subscript]Ga[0.25subscript]N epilayers at
relatively high temperature 1050 [degrees]C were studied. Indium significantly increases the doping
efficiency as shown by RT Hall measurements. RT PL measurements show a clear correlation
between emission intensity of the defect related transition and indium flow rate.
P-type conductivity has been obtained in beryllium doped GaN by MOCVD. The
activation energy of the beryllium acceptor was estimated to be 118 [plus or minus] 4 meV, which is about 40
meV less than the activation energy of the Mg acceptor in GaN.
| Identifer | oai:union.ndltd.org:KSU/oai:krex.k-state.edu:2097/431 |
| Date | January 1900 |
| Creators | Al Tahtamouni, Talal Mohammed Ahmad |
| Publisher | Kansas State University |
| Source Sets | K-State Research Exchange |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation |
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