In this thesis, we will try to grow m-plane InGaN blue light-emitting diodes (LEDs) and discuss the characteristics. First, pure m-plane GaN on the m-sapphire grown by plasma assisted molecular beam epitaxy (PAMBE) had been achieved. ¢½/¢» ratio and the growth temperature are the most important factors in the growth sequence. M-GaN film with better crystal quality was grown successfully by tuning these two factors. Indium composition in the InGaN layer is an important issue in the growth of blue LEDs; In/Ga ratio could affect the bandgap i.e. the target wavelength of a LED. We have to regard the crystal quality and the target wavelength of the InGaN layer in growth procedure. Structural properties were investigated by X-ray diffraction (XRD). XRD measurements showed that the crystal orientation of GaN films was pure m-plane. From cathodoluminescence (CL) spectra, the luminescence wavelength of InGaN layer is in the blue-light range. The crysatalline of m-plane InGaN blue LEDs were analyzed by XRD and Electron Back-Scattered Diffraction (EBSD). Electroluminescence (EL) was measured under the different inject current conditions; the polarization of EL was also measured. Moreover, the current-voltage curve and current-output curve were carried out.

We invistegated the characteristic of GaN nanostructure grown on£^-LiAlO2 substrate by molecular epitaxy beam. We observed the c-plane GaN pillar and M-plane GaN terraces assembled at the LiAlO2 substrate. It was found that the [0001 ¡Â] disk was established with the capture of N atoms by most-outside Ga atoms, while the pyramid was obtained due to the missing of most-outside N atoms. To continue, the photointensity of cathode luminescence excited from the pillar structure was one order of amplitude greater than that from M-plane.

Pure m-plane p-GaN/InGaN/n-GaN on the m-sapphire grown by plasma assisted molecular beam epitaxy (PAMBE) had been achieved. V/III ratio of the first layer m-plane GaN is 20 and growth temperature is 665 ¢XC. ¢½/¢» ratio and the growth temperature are the most important factors in the growth sequence. M-InGaN film with better crystal quality was grown successfully by tuning these two factors. We have obtained a narrow window for epitaxial growth of m-plane InGaN/GaN on m-sapphire at 450 ¢XC. The striated surface is along (1120) a-axis direction of m-InGaN epilayer. As the growth temperature is increased further to 550 ¢XC, there is no InGaN signal from x-ray diffraction (XRD). We study the effect of growth condition on the structural properties and morphology of these films using high-resolution x-ray diffractometer (XRD) and scanning electron microscopy (SEM)

The samples this thesis investigated were m-plane nitrides films grown on m-plane sapphire by plasma-assisted molecular beam epitaxy (PAMBE). Scanning electron microscopy (SEM) images revealed the surface morphologies of the films and thicknesses of the films were measured by cross-sectional scanning electron microscopy. Then we used electron back-scattered diffraction (EBSD) and X-ray diffraction (XRD) to check the growth orientation of the films. The m-plane nitrides films have the anisotropic optical properties were due to the growth orientation of the films. The films are under anisotropic stress since they were grown along m-axis and hence change the electron band structure (EBS), which resulted in anisotropic optical property. We studied the polarization properties of the luminescence at 15 K and 300 K by polarization dependent photoluminescence (PL) and calculated the degree of polarization. And then measured the strain of the m-plane nitrides films by micro-Raman spectroscopy, discussed the degree of polarization and stress. The degree of polarization larger as the anisotropic stress of the film increased.

Epitaxial m-plane (11 ¡Â00) ZnO thin films grown on m-sapphire substrates by atomic layer deposition have been studied. Atomic imaging and electron diffraction conducted in a transmission electron microscope (TEM) and crystallography by X-ray diffractometry all show consistent epitaxial relations with ZnO m-plane // sapphire m-plane, while ZnO [112 ¡Â0] // Al2O3 [0001], and ZnO [0001] // Al2O3 [112 ¡Â0]. The widths (full width at half maximum, or FWHM) of the rocking curves depend on the crystallographic axis of rotation. Dislocations near the interface between the ZnO epi-layers and sapphire substrates can be found from the cross-sectional TEM images when the direction of the incident electron beam, namely, the zone axis, is parallel to ZnO [112 ¡Â0], the a-axis of ZnO. There are stacking faults found in ZnO films away from their interfaces with the substrates. Polarization-dependent photoluminescence by differently polarized incident laser beam have also been investigated. Careful analysis of the spectra via multi-peak fittings revealed optical transitions at 3.32eV for T = 15K, which, however, shifted to 3.28eV at T = 300K. This shift in energy is accounted for by the quadratic temperature dependence of the Fermi level as determined by the positions of the lines of emission corresponding to the band edge transition. The 300K spectrum showed a more distinct peak at 2.48eV when the polarization of the emitted light was along the a-axis of ZnO, as compared to that along the c-axis of ZnO. The origin of this difference remains unaccounted for at the time of writing this thesis. The rest of the peaks have been interpreted in terms of optical transitions involving band gap impurity states, possible exciton formations, and their interactions with phonons.

This thesis will talk about the difference between c-plane and m-plane GaN. We use C-V measurement and try to find the difference from C-V result. We use atomic layer deposit (ALD) to deposit Al2O3 no n-Si (111), p-Si (111), c-GaN, m-GaN, c-InN and m-InN for making MOS structure. And use 100 kHz to measure high frequency C-V and charge-voltage method to measure quasi-static capacitance and leakage current. The process and how the instrument work will present in article. In Si (111) case, the flat-band voltage is far away from ideal value. This tells us charge in oxide. Result of quasi-static method shows interface state density is between 1011 cm-2¡DeV-1 to 1012 cm-2¡DeV-1. From Ref. 13, SiO2-Si system with 1011 cm-2 interface trap charge density for Si (111). We compare C-V carrier concentration with Hall carrier concentration and find some difference. We put C-V result of experiment and simulated with COX and Hall carrier concentration we measured. In GaN case, here is deep depletion in C-V result. And quasi-static result also shows deep depletion of GaN. This phenomenon means generate time of hole of n-type GaN is very long. And we use light to excite electron and hole and measure C-V for average surface density of state. The density of stay of Al2O3/m-GaN and Al2O3/c-GaN system is similar. Only appearance difference between Al2O3/m-GaN and Al2O3/c-GaN is position of flat-ban voltage. flat-ban voltage of c-GaN is more negative than m-GaN. For InN, we see ¡§the middle is lower than edge¡¨ curve. Recently, few group present complete C-V curve of InN. We can not sure whether we can use typical way to analyze this data.

M-plane (101 ¡Â0) ZnO thin films were grown on m-plane sapphire (101 ¡Â0) substrates by RF magnetron sputtering. We varied the RF power, working pressure, and O2/Ar ratio to obtain the best growth conditions. Structural properties were investigated by X-ray diffraction(XRD). XRD measurements showed that the crystal orientation of ZnO films was non-polar m-plane (101 ¡Â0). In addition, photoluminescence (PL) spectrum showed the bandgap energy of ZnO films was about 3.24 eV. PL spectrum showed zinc vacancy signal for films grown in oxygen rich condition. Carrier concentration was measured by hall measurement as well as FTIR spectrometry. The results showed the carrier concentration calculated by optical measurements was higher than hall measurements. One possibility for this could be the band tail at the bottom of conduction band. This band tail can make the effective mass larger and thus influencing the optical carrier concentration.

In this thesis, the growth of nonpolar m-plane zinc oxide (ZnO) nano-materials on (100) £^¡VLiAlO2 (LAO) substrates by a chemical vapor deposition (CVD) process had been studied. The mixture powders of ZnO and graphite are used as the precursor of reaction sources. Ar/O2 are used as the carrier gas and reaction gas source respectively, and the Au thin-film coated on the LAO substrate is the catalyst for the vapor-liquid-solid (VLS) growth mode. The X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to study the influence of the varied growth conditions, such as deposition time, reaction pressure, growth temperature, and the distance between substrates and reaction powder ¡K etc., on the crystal structure, surface morphology, orientation and microstructure characterizations of the ZnO nanostructure. The pure (10-10) m-plane ZnO nano-materials can be obtained at the growth parameters of 830¢XC, 10 torr, 5 minutes, and 50 sccm of Ar/O2. Furthermore, photoluminescence (PL), cathodoluminescence (CL) and Raman spectroscope (Raman) were used to study optical properties and the inner stress of the materials.

Die vorliegende Arbeit beschäftigt sich mit optischen Untersuchungen von MBE-gewachsenen hexagonalen Gruppe-III-Nitridheterostrukturen. Dafür wird die Photolumineszenz von InGaN/GaN- und GaN/AlGaN-Mehrfachquantengrabenstrukturen umfangreich zeitintegriert und zeitaufgelöst studiert. Die Proben unterscheiden sich in den Dicken der Quantengräben und Barrieren (InGaN) bzw. in der kristallografischen Orientierung (AlGaN). Als Ergebnis der großen, für das Materialsystem charakteristischen, elektrostatischen Felder zeigen die konventionell [0001]-orientierten Heterostrukturen eine verringerte Übergangsenergie und längere Lebensdauern mit zunehmender Quantengrabenbreite und höherem Indiumgehalt in den Gräben. Der beobachtete Einfluss des Quantumconfined Stark-Effektes (QCSE) auf diese Größen kann auch durch Modellrechnungen quantitativ gezeigt werden. In der Arbeit wird erstmals eine umfangreiche optische Charakterisierung einer neuartigen [1-100]-orientierten GaN-Heterostruktur auf Gamma-LiAlO2 geboten. Zum Vergleich wird das Verhalten einer identisch aufgebauten, [0001]-orientierten Struktur auf SiC ebenfalls diskutiert. Die (1-100)-Probe ist in Wachstumsrichtung frei von elektrostatischen Feldern und unterscheidet sich damit deutlich von den herkömmlichen Nitridstrukturen mit [0001]-Orientierung, deren interne Felder im MV/cm-Bereich liegen. Die spektrale Lage der Photolumineszenz bei geringen Anregungsdichten bestätigt die Flachbandsituation in der Probe. Aufgrund des bei dieser Probe nicht auftretenden QCSE ist hier eine deutlich verkürzte Lebensdauer festzustellen. Entsprechend der Auswahlregeln für hexagonales GaN weist die [1-100]-orientierte Probe eine sehr starke Polarisation der Photolumineszenz bezogen auf die Lage der [0001]-Achse auf. Die geringe Abweichung des ermittelten Polarisationsgrades von der, für A-Exzitonen in Volumen-GaN zu erwartenden, totalen Polarisation kann durch das Konfinement in den Quantengräben erklärt werden. Ein Schwerpunkt der Arbeit ist die Untersuchung der Rekombinationsmechanismen der Proben in Abhängigkeit von der induzierten Ladungsträgerdichte. Diese wird in einem Bereich von sehr geringer Dichte bis über die Mottdichte variiert. Eine Abschirmung der elektrostatischen Felder mit zunehmender Ladungsträgerdichte wird festgestellt. Dabei kann bei einer InGaN/GaN-Probe mit 3.1 nm breiten Gräben gezeigt werden, dass neben den internen piezoelektrischen Feldern die in der Literatur diskutierte Lokalisation von Exzitonen an Stöchiometrieschwankungen des Quantengrabens entscheidend die Rekombinationsdynamik in der Probe beeinflusst. Dies spiegelt sich in einer Abhängigkeit der Quantengrabeneigenschaften von den Anfangsbedingungen des Abklingprozesses und damit einem nicht existierenden allgemein gültigen Zusammenhang zwischen der Lebensdauer und der Ladungsträgerdichte wider. Die zeitaufgelösten Lumineszenzspektren der InGaN/GaN-Strukturen zeigen als Folge der mit höheren Ladungsträgerdichten zunehmenden Abschirmung eine verringerte Lebensdauer durch die vergrößerte Überlappung von Elektron- und Lochwellenfunktionen. Aufgrund der wieder abnehmenden Abschirmung während des Rekombinationsprozesses verändert sich die Lebensdauer im Laufe der Zeit. Gleichzeitig kommt es zu einer Verringerung der Übergangsenergie des Lumineszenzmaximums durch den weniger abgeschirmten QCSE. Die zeitintegrierten Photolumineszenzspektren zeigen ebenfalls eine deutliche Abhängigkeit von der Anregungsdichte. Während bei der feldfreien (1-100)-Probe keine Kompensationseffekte erwartet werden, weisen die Resultate für die konventionellen Proben auf einen, die Ladungsträgerdichte wesentlich beeinflussenden Effekt hin. Die Abhängigkeit der Intensität der Photolumineszenz von der Ladungsträgerdichte deutet ab einer bestimmten Anregungsdichte auf einen zusätzlichen Prozess, welcher die Ladungsträgerdichte reduziert, sich aber nicht im Lumineszenzspektrum widerspiegelt. Als Erklärung dafür wird die Absorption von stimulierter Emission im Substrat oder in der Pufferschicht angenommen. Bei den InGaN-Proben schiebt die Übergangsenergie mit höheren Dichten zu größeren Energien und nähert sich bis 10e5 W/cm2 einem Sättigungswert an. Dieser Wert entspricht trotz Dichten oberhalb der Mottdichte noch nicht der Flachbandsituation bei vollständig kompensierten internen Feldern. Als Ursache dafür wird der genannte, bei hohen Ladungsträgerdichten einsetzende Konkurrenzprozess gesehen. Bei den GaN/AlGaN-Proben kann im untersuchten Bereich der Anregungsdichte keine spektrale Verschiebung im Photolumineszenzspektrum festgestellt werden. Zum ersten Mal werden experimentelle Untersuchungen zur stimulierten Emission einer [1-100]-orientierten GaN-Probe durchgeführt und das optische Gewinnspektrum analysiert. Die Messungen zeigen einen maximalen Nettogewinn von ca. 50 1/cm. Aus der rechnerischen Analyse der Modenausbreitung lässt sich dafür ein Materialgewinn für GaN(1-100) von 1.1x10e4 1/cm ableiten. Die Ergebnisse zeigen außerdem, dass die Rekombination eines Elektron-Loch-Plasmas der Mechanismus für die stimulierte Emission ist. Dies entspricht dem überwiegenden Teil der in der Literatur veröffentlichten Beobachtungen für [0001]-orientierte Nitridstrukturen. Ein direkter Vergleich mit der parallel untersuchten GaN/AlGaN(0001)-Probe ist aufgrund der starken Substratabsorption nicht möglich. Es zeigt sich, dass für [1-100]-orientierte GaN-Heterostrukturen gute Ausgangsbedingungen für die Realisierung von Laserdioden gegeben sind. Zu den untersuchten Heterostrukturen wird die Wellenführung in den Proben simuliert. Bei den auf SiC gewachsenen Schichten werden die sich ausbreitenden Moden wegen des deutlich höheren Brechungsindexes des Substrates vornehmlich dort geführt. Die Überlappung der Moden mit dem aktiven Schichtpaket ist äußerst gering. Es ist für die Proben auf SiC kein optischer Gewinn zu erwarten. Die [1-100]-orientierte GaN/AlGaN-Probe besitzt eine deutlich bessere Wellenführung, da das LiAlO2 einen vergleichsweise kleinen Brechungsindex besitzt. Es wird ein Zusammenhang zwischen experimentell ermitteltem optischen Gewinn und dem Materialgewinn gebildet und das Ergebnis mit Rechnungen aus der Literatur verglichen. Ein Vorschlag für eine optimierte Wellenführung in allen untersuchten Proben wird gegeben. / In this thesis, the optical properties of molecular beam epitaxy grown hexagonal group-III nitride heterostructures are studied. The photoluminescence (PL) characteristics of InGaN/GaN and GaN/AlGAN multiple quantum well structures are investigated by time-integrated and time-resolved measurements. The analyzed specimens differ in the width of the quantum wells and barriers (InGaN) and in the crystallographic orientation (AlGaN), respectively. As a result of the large characteristic electrostatic fields, conventional [0001]-oriented heterostructures show a reduced transistion energy and longer lifetimes with increasing well width and higher Indium content in the wells. The observed impact of the Quantum Confined Stark Effect (QCSE) on these quantities is quantitatively shown in model calculations. In this work, a first extensive optical characterization of a novel [1-100]-oriented GaN heterostructure grown on Gamma-LiAlO2 is presented. For comparison, an identically designed [0001]-oriented structure on SiC is discussed. The (1-100)-grown specimen is free of electrostatic fields along the growth direction and shows a significant different behavior than conventional [0001]-oriented nitrides with internal fields of several MV/cm. The existing flat band conditions are confirmed by the spectral position of the PL at low excitation densities. Due to the non-existing QCSE at this specimen an significantly reduced lifetime is observed. A strong polarization of the PL is observed for the [1-100]-oriented sample, following the selection rules for hexagonal GaN. The small deviation of the degree of polarization from unity, which is expected in bulk GaN, is attributed to the quantum confinement in the heterostructures. One main topic of this thesis is the analysis of the recombination mechanisms of the specimens depending on the induced carrier density. The carrier density is varied from very low upto densities above the mott density. A screening of the electrostatic fields is observed with increasing carrier density. It is shown, that an InGaN/GaN heterostructure with a well width of 3.1 nm not only is influenced by internal piezoelectric fields but also the localization of excitons at stoichiometric inhomogenities in the quantum well is playing an important role for the recombination dynamics of the structure. This can be seen in the dependence of the decay process on the starting conditions. No general correlation is existing between lifetime and carrier density. Time-resolved PL measurements on InGaN/GaN heterostructures show a reduced lifetime due to an increased overlap of the electron and hole wave functions as a result of the increased screening at increasing carrier densities. During the recombination process the screening decreases again and the lifetime is changed with time. Simultaneously the transistion energy of the PL maximum is reduced by the less screened QCSE. A distinct dependence of the time-integrated PL spectra on the excitation density was also found. While there are no compensation effects expected at the (1-100) structure, which is free of electrostatic fields, the results for the conventional specimens point to an effect which influences the carrier density essentially. The dependence of the PL intensity on the carrier density points to an additional process, which comes into play at a special excitation density. This process reduces the carrier density but is invisible in the PL spectra. As an explanation we assume, that light of stimulated emission is absorbed either in the substrate or in the buffer layer. The transistion energy of the InGaN structures increases with increasing excitation density and reaches a saturation energy at a density of 10e5 W/cm2. Although this density is larger than the mott density, the transistion energy is not equivalent with a transition energy at flat band conditions. The origin of the observed effect is assumed to be the rival process, mentioned above, which comes into play at high carrier densities. For the GaN/AlGaN heterostructures no spectral shift of the PL was observed within the variation of excitation density. For the very first time, the stimulated emission of an [1-100]-oriented GaN structure was analyzed. A maximum netto gain of 50 1/cm was observed. From calculations of the mode propagation, a material gain of 1.1x10e4 1/cm is derived for GaN(1-100). Additionally from the results follows that the recombination of an electron-hole-plasma is the mechanism of the stimulated emission. This is in accordance with most of the published observations for [0001]-oriented GaN heterostructures. A direct comparison of both, the [1-100]-oriented specimen and the GaN/AlGaN(0001) structure, which was investigated parallel, was not possible. The reason for that is the strong absorption of the SiC substrate of the latter mentioned structure. It is generally shown, that [1-100]-oriented GaN heterostructures offers good starting conditions to realize laser diodes. The wave guiding was simulated for all of the used specimens. At structures grown on SiC the propagating modes are mainly guided in the substrate due to the larger refractive index of SiC with respect to GaN. The overlap of the amplified mode and the active layer is very small. No optical gain is expected for these structures. The [1-100]-oriented GaN/AlGaN structure shows a significantly improved wave guiding, due to the small refractive index of LiAlO2 in comparison with GaN. A correlation between the experimentally observed optical gain and the material gain is formed and the results are compared with the literature. A suggestion for an optimized wave guiding in all investigated specimens is given.

The popularity of III-nitride materials has taken up the semiconductor industry to newer applications because of their remarkable properties. In addition to having a direct and wide band gap of 3.4 eV, a very fascinating property of GaN is the band gap tuning from 0.7 to 6.2 eV by alloying with Al or In. The most common orientation to grow optoelectronic devices out of these materials are the polar c-plane which are strongly affected by the intrinsic spontaneous and piezoelectric polarization fields. Devices grown in no polar orientation such as (1 0 –1 0) m-plane or (1 1 –2 0) a-plane have no polarization in the growth direction and are receiving a lot of focus due to enhanced behaviour. The first part of this thesis deals with the development of non-polar epimGaN films of usable quality, on an m-plane sapphire by plasma assisted molecular beam epitaxy. Growth conditions such as growth temperature and Ga/N flux ratio were tuned to obtain a reasonably good crystalline quality film. MSM photodetectors were fabricated from (1 0 -1 0) m-GaN, (1 1 -2 0) a-GaN and semipolar (1 1 -2 2) GaN films and were compared with the polar (0 0 0 2) c-GaN epilayer. Later part of the thesis investigated (1 0 -1 0) InN/ (1 0 -1 0) GaN heterostructures. Further, we could successfully grow single composition nonpolar a-plane InxGa1-xN epilayers on (1 1 -2 0) GaN / (1 -1 0 2) sapphire substrate. This thesis focuses on the growth and characterisation of nonpolar GaN, InxGa1-xN and InN by plasma assisted molecular beam epitaxy and on their photodetection potential. Chapter 1 explains the motivation of this thesis work with an introduction to the III-nitride material and the choice of the substrate made. Polarization effect in the polar, nonpolar and semipolar oriented growth is discussed. Fabrication of semiconductor photodetectors and its principle is explained in details. Chapter 2 discusses the various experimental tools used for the growth and characterisation of the film. Molecular beam epitaxy technique is elaborately explained along with details of the calibration for the BEP of various effusion cells along with growth temperature at the substrate. Chapter 3 discusses the consequence of nitridation on bare m-sapphire substrate. Impact of nitridation step prior to the growth of GaN film over (1 0 -1 0) m-sapphire substrate was also studied. The films grown on the nitridated surface resulted in a nonpolar (1 0 -1 0) orientation while without nitridation caused a semipolar (1 1 -2 2) orientation. Room temperature photoluminescence study showed that nonpolar GaN films have higher value of compressive strain as compared to semipolar GaN films, which was further confirmed by room temperature Raman spectroscopy. The room temperature UV photodetection of both films was investigated by measuring the I-V characteristics under UV light illumination. UV photodetectors fabricated on nonpolar GaN showed better characteristics, including higher external quantum efficiency, compared to photodetectors fabricated on semipolar GaN. Chapter 4 focuses on the optimization and characterisation of nonpolar (1 0 -1 0) m-GaN on m-sapphire by molecular beam epitaxy. A brief introduction to the challenges in growing a pure single phase nonpolar (1 0 -1 0) GaN on (1 0 -1 0) sapphire without any other semipolar GaN growth is followed by our results achieving the same. Effect of the growth temperature and Ga/N ratio on the structural and optical properties of m-GaN epilayers was studied and the best condition was obtained for the growth temperature of 7600C and nitrogen flow of 1 sccm. Strain in the film was quantitatively measured using Raman spectroscopy and qualitatively analyzed by RSM. Au/ nonpolar GaN schottky diode was fabricated and temperature dependent I-V characteristics showed rectifying nature. Chapter 5 demonstrates the growth of (1 0 -1 0) m-InN / (1 0 -1 0) m-GaN / (1 0 -1 0) m-sapphire substrate. Nonpolar InN layer was grown at growth temperature ranging from 3900C to 440C to obtain a good quality film at 4000C. An in-plane relationship was established for the hetrostructures using phi-scan and a perfect alignment was found for the epilayers. RSM images on the asymmetric plane revealed highly strained layers. InN band gap was found to be around 0.8 eV from absorption spectra. The valance band offset value is calculated to be 0.93 eV for nonpolar m-plane InN/GaN heterojunctions. The heterojunctions form in the type-I straddling configuration with a conduction band offsets of 1.82 eV. Chapter 6 focuses on the optimization of nonpolar (1 1 -2 0) a-GaN on (1 -1 0 2) r-sapphire by molecular beam epitaxy. Effect of the growth temperature and Ga/N ratio on the structural and optical properties of a-GaN epilayers was studied and the best condition was obtained for the growth temperature of 7600C and nitrogen flow of 1 sccm. An in-plane orientation relationship is found to be [0 0 0 1] GaN || [-1 1 0 1] sapphire and [-1 1 0 0] GaN || [1 1 -2 0] sapphire for nonpolar GaN on r-sapphire substrate. Strain in the film was quantitatively measured using Raman spectroscopy and qualitatively analyzed by RSM. UV photo response of a-GaN film was measured after fabricating an MSM structure over the film with Au. EQE of the photodetectors fabricated in the (0 0 0 2) polar and (1 1 -2 0) nonpolar growth directions were compared in terms of responsively, nonpolar a-GaN showed the best sensitivity at the cost of comparatively slow response time. Chapter 7 demonstrates the growth of non-polar (1 1 -2 0) a-plane InGaN epilayers on a-plane (1 1 -2 0) GaN/ (1 -1 0 2) r-plane sapphire substrate using PAMBE. The high resolution X-ray diffraction (HRXRD) studies confirmed the orientation of the films and the compositions to be In0.19Ga0.81N, In0.21Ga0.79N and In0.23Ga0.77N. The compositions of the films were controlled by the growth parameters such as growth temperature and indium flux. Effect of variation of Indium composition on the strain of the epilayers was analyzed from the asymmetric RSM images. Further, we report the growth of self-assembled non-polar high indium clusters of In0.55Ga0.45N over non-polar (1 1 -2 0) a-plane In0.17Ga0.83N epilayer grown on a-plane (1 1 -2 0) GaN / (1 -1 0 2) r-plane sapphire substrate. The structure hence grown when investigated for photo-detecting properties, showed sensitivity to both infrared and ultraviolet radiations due to the different composition of InGaN region. Chapter 8 concludes with the summary of present investigations and the scope for future work.