Synthesis, Characterization and Evaluation of Zinc-Amides as Potential Dopant Sources for ZnSe OMVPE
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SYNTHESIS, CHARACTERIZATION AND EVALUATION OF ZINC-AMIDES AS POTENTIAL DOPANT SOURCES FOR ZnSe OMVPE. WILLIAM S. REES, JR.,' DAVID M.GREEN AND WERNER HESSE Department of Chemistry and Materials Research and Technology Center, The Florida State University, Tallahassee, Florida 32306-3006, U.S.A. TIMOTHY J. ANDERSON AND BALU PATHANGEY Department of Chemical Engineering and MICROFABRITECH, The University of Florida, Gainesville, Florida 32611-2022, U.S.A. ABSTRACT Compounds of the general forms Zn[N(R) 2]2, Zn[N(R)(R')] 2 and Zn{[N(R) 2](N(R') 2]} have been prepared, these new compositions have been characterized by multinuclear NMR, GC/MS, FTIR, elemental analysis and single crystal x-ray diffraction, and they have been evaluated for their potential to serve as "designer dopants" in the epitaxial growth of p-type ZnSe. Retention of the Zn-N bond during deposition should insure selective location of the nitrogen atom on the native selenium lattice site. Precursor vapor pressures, vapor phase decomposition mechanisms, and thin film properties are presented. Results from materials characterization by XRD, SIMS, PL, Raman and SEM are presented in the context of evaluating dopant level. INTRODUCTION In recent publications 1 ,2 we have described the concept of "designer dopants" for use in the preparation of selenium site specific nitrogen doped ZnSe. The concept is to capitalize on the known absence of an anti-site defect structure for zinc in this material by pre-bonding the zinc and nitrogen atoms. Thus, if the Zn-N bond can be encouraged to remain intact throughout the growth process, the nitrogen atoms will be forced to reside on a lattice site adjacent to a native zinc site - i.e., on the desired native selenium site. Our initial efforts in this new area focused on utilization of the known compound Zn(N[Si(CH 3 )3] 2}2 , bis(bis(trimethylsilyl)amido)zinc, or TMSAZ, as the potential dopant source. 3 Subsequent preparation 4 of several compounds in the homoleptic zinc bis-amide series Zn{N[(Si(CH 3)3)(R)]} 2 , specifically those for R = t-Bu and i-Pr, led to an exploration of their potential to serve inthe same capacity. 3 The early research in preparation of p-type ZnSe by OMVPE has been summarized previously. The motive in much of this research has been the search for a materials system which will serve to fabricate optoelectronic and electroluminescent devices which operate in the blue region of the visible spectrum. Among the potential materials, ZnSe has emerged recently as a leading contender for near term commercialization. 5 The bulk of these new devices have relied on MBE techniques for preparation. Due to the inherent advantages of OMVPE-based approaches for large scale implementation of these successes, we have pursued the designer dopant avenue of research. These advantages include: uniform coatings over large surface areas, depositions on non-planar substrates, economy of scale in ease of high throughput systems and reliance on non-UHV techniques which reduce deposition instrumentation complexity. 6 A deta
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