The carrier dynamics of Indium Nitride thin films has been studied by the ultrafast time-resolved photoluminescence upconversion. The silicon-doped InN thin films were grown on GaN buffers and sapphire substrates with the background carrier densities of varies from 6.16¡Ñ1018 cm-3 to 1.27¡Ñ1020 cm-3. This thesis found that as the background increases, the peak energy of the photoluminescence of the InN samples exhibits blue shift, the decay time decreases, and the emission time of the effective longitudinal optical phonon by carriers increases from 358 to 775 fs. The studies of InN thin films which were grown on r-plane substrate without buffer layers indicate that the decay time as well as the LO phonon emission time of the zinc-blende InN are shorter than those of the wurtzite InN. The large number of defect states in the wurtzite structure and highly doped InN thin films is attributed to the fast decay time and long LO phonon emission time. II

Unintentionally doped InN thin films have been epitaxially grown on Si (111) by plasma-assisted molecular-beam epitaxy (PAMBE) with AlN buffer layers. The optical characteristics were investigated with photoluminescence (PL). In analyzing the PL spectra, we look into the variations in peak positions, intensities, and full¡Ðwidth ¡Ðat¡Ðhalf maximum (FWHM) by changing the temperature and the laser power. To cover both the visible and IR spectral ranges, two different detectors were used, PMT for the visible and PbS for the near-IR. A single namely, dominant peak was found in the near-IR regime. The temperature dependent PL line-shape is fitted with the Varshni equation. Excitation laser power dependent PL is found to follow a linear relation. The energy band gap of InN is inferred from the optical measurements.

Unintentionally doped InN thin films have been epitaxially grown on Al2O3 (001) and Si (111) by plasma-assisted molecular beam epitaxy (PAMBE).In this thesis, all the samples are two luminenscent peaks. In analyzing the PL spectra, we look into the variations in peak position, intensities by changing the temperature and the laser power, and PbS detector was used. The temperature dependent PL peak position versus temperature is fitted with Varshni equation. Excitation laser power dependent PL is found to follow a linear relation. The two luminescent peaks of InN are discussed by optical measurement.

In this thesis, we will discuss how to grow InN nanorods. We have tried different parameters to grow InN nanorods on silicon (111) substrate by plasma assisted molecular beam epitaxy (PAMBE). The growth temperature and V/III ratio are the most important factors in growth. By changing these two factors, we can grow InN into different forms. Another factor of forming InN nanorod is AlN buffer layer. Growing without AlN buffer layer, InN nanorods can be removed from substrate very easily. Growing with AlN buffer layer, the interface between InN nanorods and silicon substrate seems stronger. After a long time growth, the bottoms of InN nonarods combine together. Therefore, the morphology of this sample seems like InN nanorods grown on InN film. From XRD measurement, we can know the InN nanorod is growing alone the c-axis. Without the signal of In metal shows InN nanorod were grown under the N-rich condition. We found that the peak position of PL spectra is about 0.66 eV. And did not have any shift while the temperature changing. Measuring CL spectra of areas with different diameters of single InN nanorod, we got almost the same result. The peak positions are around 0.63 eV. We calculate the quantum size of InN for having quantum effect is about 17 nm. Maybe it is one of the reasons of peak positions did not get shift while diameter changing. In Raman spectra, the E2(high) peak of InN nanorod is 488.23 cm-1, it is closer to the unstrained InN (488 cm-1) than InN film.

Zugl.: Passau, Universiẗat, Diplomarbeit, 2002.

Indium nitride (InN) is a group III-V semiconductor that is part of the Al,Ga:N family. It is an infrared bandgap semiconductor with great potential for use in photovoltaic applications. Being an intrinsically n-type material, p-type doping is naturally one of the ongoing hot topics in InN research, which is of interest in the fabrication of pn junctions. Plasma-assisted molecular beam epitaxy (PAMBE) grown Mg doped InN thin film was investigated via systematic optical characterizations. Photoluminescence (PL) measurement has been a key part of the research, exhibiting a wide range of spectral lines between 0.54 and 0.67 eV. In a critical Mg concentration range of 2.6×10¹⁷ and 1.0×10¹⁸ cm⁻³, a strong luminescence line at 0.6 eV has been associated with a Mg-related deep acceptor. Correspondingly, a variable magnetic field Hall (VFH) effect measurement has successfully probed a buried hole-mediated conductivity path underneath a surface electron accumulation layer. This specific doping range also led to a manifestation of a “true” band-to-band transition at 0.67 eV. Such an observation has not previously been reported for InN and in our case this assignment is convincingly supported by the quadratic characteristic of the excitation power law. This established that a rigorous control of Mg flux can sufficiently compensate the background electron concentration of InN via the substitutional incorporation on In sites (Mg_In). However, introduction of donor-like complexes somewhat suppressed this process if too much Mg or even alternative dopants such as Zn and Mn were used. Also distinctively observed was a strongly quenched PL quantum efficiency from heavily doped films, where time-resolved differential transmission (TRDT) measurement showed a biexponential carrier lifetime decay curve owing to the onset of Auger recombination processes. These observations certainly have profound implications for devices and beyond.

In this research, X-ray Diffraction is used to detect the existence of the In metal signal of the Indium Nitride (InN) through the analysis of two samples grown from the plasma-assisted molecular beam epitaxy (PAMBE). Sample A was grown on the Al2O3(0001) substrate with Gallium Nitride as a buffer layer, while Sample B was grown directly on the Si(111) substrate. Through X-ray Diffraction, we discovered the In(101) signal on Sample A and the InN(10-11) signal on Sample B. However, the two peaks of both signals were so close that it was difficult to differentiate them. Besides, the scanning electron microscope failed to show the existence of the In metal on the surface of both InN samples. Therefore, the high temperature XRD was employed to identify the true signal based on the different melting points between InN and In. Further, an acid etching method was also applied to recognize the existence of the In metal on the surface of the sample.

As the device size getting nanoscale, quantum dot structure had become one kind of new method of semiconductor manufacturing technology. In this thesis, two series of self-assembled InN quantum dots were grown by plasma-assisted molecular beam epitaxy (PAMBE) on GaN thin film, based on sapphire(0001) substrate. GaN thin films were characterized by the reflection high energy electron diffraction (RHEED) and scanning electron microscope (SEM). Samples with smooth epitaxial GaN thin films were obtained. Then, InN quantum dots were grown on epitaxial GaN thin film. We have prepared two series of samples. According to the results of the high resolution X-ray diffractometer (HR-XRD) and RHEED patterns, InN structure can be successfully grown on the GaN thin film surface. First series contained samples with InN layer with different thickness and changes of surface morphology were found with increase of InN layer thickness. The second series contained samples with multiple InN layers of the same thickness. Results of atomic force microscopy (AFM), RHEED patterns and SEM, show that InN quantum dots were grown as Stranski-Krastanow growth mode.

We discuss the PL spectra of the InN band gap. The InN thin film epitaxy grows on both Si (111) and sapphire (0001) by the PA-MBE (molecular beam epi). We change different grown conditions to improve the sample quality. In experiment part, the first step is to make sure the sample is really InN, using X-ray diffraction. And then we compare the quality of all sample, by the FWHM of X-ray diffraction rocking curve and the SEM pictures.

InN is a semiconductor material of vary high electron mobility, so InN have potential for high speed electronic device. But the bandgap is not sure. We use photoreflectance spectroscopy to investigate bandgap of InN at different temperature. We use third derivative reflectance formula of low field to fit experimental data and appraisal the type of electron transition.