ICMCTF2004 Session D1-3: Carbon Nitride, Boron Nitride and Other Group-III Nitride Materials

Tuesday, April 20, 2004 8:30 AM in Room Royal Palm 4-6

Tuesday Morning

Time Period TuM Sessions | Abstract Timeline | Topic D Sessions | Time Periods | Topics | ICMCTF2004 Schedule

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8:30 AM D1-3-1 Material Properties of GaN and Related Materials Grown on Silicon by MBE
F. Semond, F. Natali, S. Joblot, Y. Cordier, J. Massies (CRHEA-CNRS, France)

GaN-based devices (LEDs, LDs, HEMTs, ...), usually grown on sapphire or silicon carbide substrates, have now a large impact on semiconductor industry development. The growth of device-quality GaN-based heterostructures on silicon substrates would be of huge importance in terms of cost, availability, processing and integration. This is the reason why more and more fundamental as well as industrial research groups are now involved in the development of GaN epitaxial growth on silicon substrates. In contrast to classical III-V compounds like GaAs and InP, GaN-based devices are well known for their exceptional material robustness as illustrated by their very good characteristics despite the presence of high dislocation densities. Therefore, in case of a successful growth of GaN on silicon, GaN-based electronics and optoelectronics as well as the integration of Si- and GaN-based devices on the same chip becomes feasible.

To achieve high-quality GaN-based epitaxial films on silicon substrates, a specific growth process must be developed in order to overcome several difficulties: - the silicon surface is very reactive to both, group III elements and nitrogen related species used during the growth, -the large lattice mismatch produces a huge amount of dislocations, - the large difference in the thermal expansion coefficient introduces an important tensile stress in GaN-based epitaxial layers. By using Molecular Beam Epitaxy and ammonia as the nitrogen precursor, a process was developed for the growth of device-quality GaN layers on silicon (111) substrates. This growth process which has been proven very efficient in terms of epitaxial relationship, polarity control, dislocation density reduction, quality of surfaces and interfaces and tensile strain compensation, will be discussed. In particular, details about the AlN nucleation conditions and the buffer layer stacking which are found to be key parameters will be presented. Structural, optical and electrical properties of GaN films and heterostructures will be discussed and device results [1-3] obtained in collaboration with partners will be shown.

[1]. Observation of rabi splitting in a bulk GaN microcavity grown on silicon N. Antoine-Vincent et al., Phys. Rev. B 68, 153313 (2003)

[2]. AlGaN/GaN HEMTs on Si(111) with 6.6 W/mm output power density R. Behtash et al., Electronics Letters. 39, 626 (2003)

[3]. Microcavity light emitting diodes based on GaN membranes grown by molecular beam epitaxy on silicon J.-Y. Duboz et al., Jpn. J. Appl. Phys. 42, 118 (2003)

9:10 AM D1-3-3 Heteroepitaxy of GaN on Si(111) Realized by Coincident-interface AlN/Si3N4(0001) Double Buffer Layer
C.L. Wu, J.-C. Wang, M.-H. Chan, T.T. Chen, S. Gwo (National Tsing-Hua University, Taiwan, R.O.C.)
We present a stacked buffer mechanism for heteroepitaxial growth with large lattice mismatch. The stacked buffer consists of constituent layers, which can form coincident lattices at layer/layer and layer/substrate interfaces. For the case of GaN-on-Si(111) heteroepitaxy, we utilize the 1:2 and 5:2 coincident lattices formed at the Si3N4(0001)/Si(111) and AlN(0001)/Si3N4(0001) interfaces respectively to facilitate the double buffer layer for GaN-on-Si heteroepitaxial growth. By using this buffer technique, we resolve the issue of autodoping, resulting from Al/Si and Ga/Si interdiffusion when grown with a single AlN(0001) buffer. As a result, the epitaxial quality of GaN film is also significantly improved.
9:30 AM D1-3-4 Heteroepitaxial Growth of Wurtzite InN Films on Si(111) Exhibiting Strong Near-infrared Photoluminescence at Room Temperature
C.H. Shen, C.L. Wu, S. Gwo (National Tsing-Hua University, Taiwan, R.O.C.); W.H. Chang, T.M. Hsu (National Central University, Taiwan, R.O.C.)
High-quality InN epitaxial films have been grown by nitrogen-plasma-assisted molecular–beam epitaxy on Si(111) substrates using a new buffer technique. Growth of a (0001)-oriented single crystalline wurtzite-InN layer was confirmed by reflection high-energy electron diffraction, Raman scattering, and X-ray diffraction. At room temperature, these films exhibited strong near-infrared (0.7-1.0 eV) photoluminescence (PL). In contrast to the previous report, no PL signal was observed at ~1.9 eV, which is the previously assumed fundamental band gap of wurtzite-InN. The PL signal was found to depend linearly on the excitation laser intensity over a wide intensity range (three orders of magnitude), indicating that the nature of the observed PL is most likely due to the emission of direct band-to-band recombination rather than the band-to-defect (or impurity) deep emission.
9:50 AM D1-3-5 Polarity and Surface Control in MBE Growth of III-Nitrides for Electron Device Application
H. Okumura, X.Q. Shen (Power Electronics Research Center (PERC), National Ins.t of Adv. Industrial Sci. & Tech. (AIST), Japan)

Recently, Nitride semiconductors, such as GaN, AlN and AlGaN, have attracted much attention aiming at high-frequency and high-power electronic devices as well as optoelectronic devices. The major growth technique for these applications has been metalorganic chemical vapor deposition (MOCVD). On the other hand, molecular bean epitaxy (MBE), which is well-known to be another advanced technology for semiconductor thin film growth, has been behind MOCVD for the growth of nitrides, because of the poor quality of the grown films.

However, for these several years, various kinds of compact plasma sources have been developed as a N source, and the understanding of the growth mechanism has been much advanced. We have clarified the importance of lattice polarity for the growth of nitrides by MBE, and achieved the drastic improvement of film quality, which enabled us the fabrication of high-frequency heterojunction field effect transistor (HFET) by using MBE-grown nitride films.

In this talk, I will reviewed the present status of MBE technique for nitride film growth, and their application to electron devices, including our recent results related with structure characterization and device fabrication.

10:30 AM D1-3-7 Structural, Optical and Field Emission Properties of AlN Nanotips
S.C. Shi, C.F. Chen (National Chiao Tung University, Taiwan, R.O.C.); K.H. Chen (Academia Sinica, Taiwan, R.O.C.); L.C. Chen (National Taiwan University, Taiwan, R.O.C.)
In this report the structural, optical and field emission (FE) properties of AlN nanotips were reported. The nanotips were grown on the silicon substrate with Au as catalyst utilizing a thermal chemical vapor deposition system. The size control of the nanotips can be achieved by simply adjusting the thickness of catalyst layer when other growth parameters such as temperature and gas flow rates are fixed. Structural studies by high resolution transmission electron microscopy, scanning electron microscope, X-ray diffraction, and Raman spectroscopy of the nanotips were presented. Optical properties were obtained from cathodoluminescence. Near band-edge transitions at about 6.19eV and 6.08eV were investigated and a very strong 3.4eV luminescence, which is attributed to incorporation of oxygen in the nanotip, was observed. FE properties of AlN nanotips, grown on four kinds of Si substrates (n-, n+-, p-, and p+-type) were studied, for the comparison of the role of majority carriers in the Si substrates. The AlN nanotips grown on p+-type Si substrate showed the lowest turn-on voltage. In contrast, it is difficult to obtain any field emission current of the AlN nanotips grown on n- and n+-type Si substrate. The model of carrier transfer between Si-AlN interfaces was proposed. Finally, the stability of FE from AlN nanotips was demonstrated.
10:50 AM D1-3-8 Size and Shape Controlled GaN Nanocrystals Grown by Reactive Epitaxy on Si3N4/Si(111)
C.L. Wu, L.J. Chou, S. Gwo (National Tsing Hua University, Taiwan, R.O.C.)
We report the investigation of coherent and faceted GaN nanocrystals spontaneously formed by nitrogen-plasma-assisted reactive epitaxy with Ga droplets on the single-crystal Si3N4(0001)/Si(111) surface. The size and shape distribution of GaN nanocrystals, as revealed by atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (XTEM), is bifurcated in size (mean diameters of 14 and 25 nm) and shape and the distribution widths are significantly narrower than that of Ga droplets predeposited in the Volmer-Weber growth mode. Furthermore, using high-resolution AFM and XTEM images of supported nanocrystals and the method of Wulff construction, we determine the size-dependent equilibrium shapes of bimodal size distribution as well as the relative facet energies.
11:10 AM D1-3-9 Synthesis of Dilute Magnetic Semiconductors for Spin Injection Into GaN-Based Devices
C.R. Abernathy, G.T. Thaler, R. Frazer, G. Gila, J. Kim, S.J. Pearton, F. Ren (University of Florida); Y.D. Park (Seoul National Univeristy, South Korea)
Future spintronic devices will likely require injection of polarized currents into semiconductor devices. Though significant work has been carried out in GaAs-based materials, the rapid advancement of GaN-based devices for visible light emission and high power electronics makes this an attractive system for investigation. The recent realization of room temperature ferromagnetism in GaN doped with transition metals such as Mn or Cr has ignited interest in the development of magnetic devices based on the use of dilute magnetic semiconductors (DMS) as the injection layer. Optimization of the DMS material in terms of choice of dopant, magnetic characteristics and crystalline quality is necessary before device fabrication can be undertaken. In this paper we will discuss the synthesis and characterization of GaN and AlN doped with a variety of transition metals. Gas-source molecular beam epitaxy using an RF nitrogen plasma source along with elemental sources for Ga, Al, Cr and Mn have been used to deposit thin films on MOCVD GaN buffer layers. Conditions for depositing single phase material with optimum magnetic ordering will be described, as will the beneficial effects of co-doping with oxygen. The processing challenges associated with integrating these materials into standard GaN/AlGaN light emitting diodes (LEDs) will be discussed along with preliminary electroluminescence results from SpinLEDs fabricated using only low temperature processing. Prospects for other spintronic devices such as tunneling magnetoresistance (TMR) structures will also be discussed. This work was supported by the U. S. Army Research Office (ARO-DAAD19-01-1-0701) and NSF (ECS-0224203).
11:50 AM D1-3-11 Growth, Self-ion Implantation and Luminescence Properties of GaN Nanorods and Nanowires
L.C. Chen, C.S. Shen, S.C. Shi (National Taiwan University, Taiwan, R.O.C.); S. Dhara, C.T. Wu, K.H. Chen (Academia Sinica, Taiwan, R.O.C.); C.W. Hsu, C.C. Chen (National Taiwan Normal University, Taiwan, R.O.C.)
GaN nanowires and nanorods, or other one-dimensional (1D) semiconductor nanostructures in general, have been a subject of current interest because the strong confinement of electrons, holes and photons makes them particularly attractive as potential building blocks for nanoscale electronics and optoelectronic devices. Single-crystalline GaN and related 1D nanostructures, specifically, binary InN, AlN along with their ternary In1-xGaxN and In1-xAlxN counterparts have been successfully grown by catalytic chemical vapor deposition. Their structure and optical properties are investigated by scanning and transmission electron microscopy, Raman, photoluminescence (PL) as well as cathodoluminescence (CL) techniques. Diameter and position selective growth of these 1D nitride nanostructures has been demonstrated by pre-treatment of the substrate surface with size-controlled catalyst. Oriented growth of the nanorods was also obtained under hetera- or homo-epitaxial conditions. While PL measurements usually give spectral data from numerous nanowires and nanorods with a broad distribution of diameter, the CL measurements (from room temperature down to 4 K) can easily be performed on "single-object". A higher CL peak position of individual GaN nanorod than that of bulk GaN film was observed, indicating the presence of strain in the pristine nanorod, which is also confirmed by X-ray diffraction analyses. In addition, a blue shift of CL peak position with decreasing the diameter of GaN nanorod was noticed. However, the magnitude of the peak shift is much more pronounced than that estimated from quantum confinement. Finally, Ga+ ions implantation of these GaN 1D nanostructures has been studied using 50-keV Ga+ focused ion beam. Phase transformation and defect structure evolution as a function of irradiated ion-beam fluence is also investigated by electron-microscopy-based techniques.
Time Period TuM Sessions | Abstract Timeline | Topic D Sessions | Time Periods | Topics | ICMCTF2004 Schedule