Lumenz Inc.

Boston, MA, United States

Lumenz Inc.

Boston, MA, United States
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Stevie F.A.,North Carolina State University | Maheshwari P.,North Carolina State University | Pierce J.M.,Lumenz Inc. | Adekore B.T.,Lumenz Inc. | Griffis D.P.,North Carolina State University
Surface and Interface Analysis | Year: 2013

Zinc oxide (ZnO) is a wide band gap semiconductor that shows great promise for development of light emitting diode structures. Interest in this technology has increased significantly, but even though controlled n-type doping can be readily achieved, p-type doping has been difficult. Numerous potential p-type dopants were investigated in this SIMS study using a CAMECA IMS-6F. The dopants and other elements of interest were quantified by use of ion implantation into ZnO substrates. Relative sensitivity factor values were obtained for H, Li, N, F, Na, Mg, Al, Si, K, Ga, As, Se, Ag, Cd, Te. Sample charging was encountered for some specimens, and adjacent electron neutralization procedures were employed. ZnO structures were prepared and subsequently analyzed with both O2+ and Cs+ primary beams. Depth profiles exposed a number of analysis issues. Because of the large number of elements, especially those at low atomic number, that were present in the structures, many mass interferences were encountered. Ag in particular was very difficult to monitor. Matrix effects were also noted, especially when high Mg doping was used. The need to monitor Al, Na, and K in the near surface region required analysis without conductive Au coating to reduce contamination. With careful choice of secondary ion species, it was possible to monitor the elements of primary interest using O2+ primary beam. SIMS demonstrated the ability to characterize the layers in the ZnO structure, including quantum wells, and to determine dopant and contaminant levels. Copyright © 2012 John Wiley & Sons, Ltd. Copyright © 2012 John Wiley & Sons, Ltd.

Tresback J.,Lumenz Inc. | Pierce J.M.,Lumenz Inc. | Ali Y.S.,Lumenz Inc. | Krahnert A.,Lumenz Inc. | And 3 more authors.
Journal of the Electrochemical Society | Year: 2011

The wet and dry etch rates of Ga-doped ZnO and MgxZn 1-xO deposited on r-plane sapphire by metalorganic vapor phase epitaxy (MOVPE) were studied for magnesium content 0 ≤ x ≤ 0.3 using dilute phosphoric acid and halogen-based inductively coupled plasma reactive ion etching (ICP-RIE) respectively. A decrease in the dry etch rates with increasing magnesium content was observed along with relatively low thermal activation energies of 21, 25, and 55 meV corresponding to n-ZnO, n-Mg 0.1Zn0.9O, and n-Mg0.3Zn0.7O films respectively. Conversely, wet etch rates increased with increasing magnesium content with corresponding thermal activation energies of 8.4, 5.5, and 4.3 kCalmol for n-ZnO, n-Mg0.05Zn0.95O, and n-Mg 0.1Zn0.9O epilayers respectively. The dominant rate-limiting step was determined to be ion-assisted desorption of the etch products including (Mg, Zn) Cl2 during ICP-RIE etching and the wet etch process transitioned from reaction rate-limited to diffusion rate-limited etching with increasing magnesium content. © 2011 The Electrochemical Society.

Pierce J.M.,Lumenz Inc. | Wen H.,Lumenz Inc. | Liu K.,Lumenz Inc. | Kumrr M.,Lumenz Inc. | And 4 more authors.
Journal of Crystal Growth | Year: 2011

We report on the epitaxial growth of ZnO and MgxZn 1-xO films grown epitaxially on (1 0 1̄ 0) ZnO substrates for 0≤x≤0.50 via a metal organic vapor phase epitaxy (MOVPE) process. Morphological properties of these epilayers investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM) indicate step-flow growth mode. Structural analysis conducted by high resolution X-ray diffraction (HRXRD) and transmission electron microscopy (TEM) indicates monocrystalline deposition and increasing biaxial strain with increase in Mg concentration. In particular, TEM indicates the prevalence of stacking faults as the main strain defects in MgxZn1-xO epilayers. Temperature-dependent photoluminescence studies identify neutral donoracceptor pair transitions occurring in Mg0.20Zn0.80O at 3.45 eV corresponding to an acceptor energy of 211 meV. Acceptor profiles measured by secondary ion mass spectrometry (SIMS) reveal the presence of dopant diffusion. © 2011 Elsevier B.V.

Liu K.,Lumenz Inc. | Pierce J.M.,Lumenz Inc. | Ali Y.S.,Lumenz Inc. | Krahnert A.,Lumenz Inc. | Adekore B.T.,Lumenz Inc.
Journal of Applied Physics | Year: 2011

Hexagonal wurtzite MgxZn1-xO intrinsic and gallium-doped epilayers were deposited on m-plane ZnO substrates by metalorganic vapor phase epitaxy. We demonstrate a linear dependence in the energy gap with increasing Mg concentration for n-type alloys 0.10 ≤ x ≤ 0.30 and for intrinsic alloys 0.20 ≤ x ≤ 0.50. We show a comparison of m-plane and c-plane MgxZn1-xO indicating a dependence of the electronic activity of Mg with crystallographic orientation. Further, we demonstrate an increase in exciton localization associated with the strong enhancement of photoluminescence intensity and reduction in the near band-edge full-width at half-maximum with increasing Mg concentration. Additionally, the thermal activation energy corresponding to the localization is considered. © 2011 American Institute of Physics.

Lumenz Inc. | Date: 2010-11-22

Methods of forming planar zinc-oxide based epitaxial layers, associated heterostructures, and devices are provided.

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