| Summary: | 博士 === 國立交通大學 === 材料科學與工程學系所 === 101 === Indium nitride is a III-V semiconductor which is potential for optoelectronics and electronics application due to its high electron mobility, high peak drift velocity, low effective electron mass and narrow bandgap of 0.65 ~0.7 eV. InN has been grown using metalorganic chemical vapor deposition (MOCVD) and molecular beam epitaxy (MBE). It has been known that InN has a low dissociation temperature at 600 ℃, such that the growth temperature is limited by the desorption of nitrogen and the thermal decomposition of the films. Therefore, the high-quality InN is usually obtained by using MBE.
Various processing parameters may affect the quality of InN, such as substrate, buffer layer, substrate temperature, pressure, and V/III flow ratio. In this study, polar and semipolar InN films were prepared by plasma-assisted metal-organic molecular beam epitaxy (PA-MOMBE) which can have a high growth rate. Detailed characterizations of structural and optical properties of the grown polar/semipoar InN films were carried out.
The results indicated that In-polar InN films grown with the V/III ratio of ∼1.81 has the smallest full width at half maximum (FWHM) value of 455 arcsec for (0002) X-ray rocking curve (XRC) andFWHMs value of 1070 arcsec for (10-12). The epitaxial relationship of InN with GaN substrate is (0002)InN//(0002)GaN and [11-20]InN//[11-20]GaN as determined by selected area electron diffraction. Additionally, secondary ion mass spectrometry and X-ray photoelectron spectroscopy results on all the deposited films showed that carbon and hydrogen of average concentration were measured in the order of magnitude of about 10^20 cm^-3 and O concentration about 1019 cm^−3. Also, the C and H concentrations increase with increasing trimethylindium flow rate. A relatively high concentration of C, H and O exists near the surface of the InN films. After etching of the InN films, a decreased carrier concentration to 3.31 × 10^19 cm^−3 can be obtained, while the corresponding electron mobility can increase to 335 cm^2/V-s. Optical properties showed that the PL spectra exhibited NBE peak in the range of 0.692 ~ 0.735 eV. Also, the peaks showed blue-shift with increasing V/III flow ratio.
Semipolar InN(10-13) films were prepared on LaAlO3(112) substrate by varying the substrate temperature. The results show that semipolar InN(10-13) layers can be grown at 510 ℃ with the (0002) FWHMs value of 1830 arcsec and (10-13) XRC FWHMs value of 1408 arcsec. Also, the InN film is in epitaxy with LAO substrate with orientation relationships of InN(10-13)//LAO(112) and [1-210]InN// [11-1 ]LAO. The lattice mismatch between InN and LAO can then be estimated to be 7.75 % along the [1-210]InN direction and 0.2 % along the [-3032]InN direction. Electronic properties showed that the InN film grown at 510 ℃ exhibits the highest electron mobility of 494 cm2/V-s and lowest carrier concentration of 2.4 × 10^19 cm^-3. PL spectra at 10 K showed the peaks of near band-edge emission at energies between 0.72 - 0.81 eV. However, InN grown at 510 °C has the highest peak intensity and the narrowest FWHM of these samples which has better quality.
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