Organometallic Chemical Vapor Deposition of Gaas Using Novel Organometallic Precursors
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ORGANOMETALLIC CHEMICAL VAPOR DEPOSITION OF GaAs USING NOVEL ORGANOMETALLIC PRECURSORS
R. A. JONES*, A.H. COWLEY, B. L. BENAC*, K. B. KIDD*, J. G. EKERDT **, AND J. E. MILLER Departments of Chemistry* and Chemical Engineering", The University of Texas at Austin, Austin, Texas 78712
ABSTRACT The goals of the research are the design and synthesis of a new class of precursor compounds for III/V compound semiconductor materials, growth of films with these precursors and developoment of an understanding of the relationships between precursor structure, film growth reactions and film properties. Conventional OMCVD of III/V compound materials has a number of inherent safety and processing problems associated with the group III alkyl and group V hydride sources. Our approach to these problems is the synthesis of a single precursor with a fixed III:V stoichiometry and a direct two-center, two-electron sigma III-V bond., These, compounds have the general formula,[R 2 M(R 2 E)] 2 and R 2 M(R 2 E) 2 M R2 (MM = Al, Ga, In; E=P,As; R,R = alkyl, aryl). The III-V bond in these compounds is stronger than the other bonds and the minium deposition temperature can be controlled by employing subsituents that undergo facile hydrocarbon elimination. A typical example is the use of [Me 2 Ga(L-t-Bu 2 As)] 2 as the single source for GaAs films. The organometallic precursor is a solid crystalline powder which is maintained at 130 0 C to generate enough vapor for OMCVD. Typical film growth conditions involve the use of H2 or 0 He as the carrier gas, substrate temperatures of 500 to 700 C, and a total system pressure of 0.0002 Torr. GaAs(100), Si(100) (As-doped 30 off toward (011) and quartz have been used as substrates. Film composition has been established with XPS. The Ga 3d, As 3d, and C ls signals at 18.8, 40.9, and 284.6 eV, respectively, reveal the films to be 1:1 Ga:As and void of carbon. The carbon levels are less than 1000 ppm. X-ray diffraction and SEM results suggest polycrystalline GaAs on quartz and epitaxial GaAs on GaAs(100) and Si(100) . (2 K) photoluminescence measurements on GaAs, grown on semi-insulating GaAs(100) and Si-doped GaAs(100) at 570 0 C. produce PL signals indicating that crystalline domains are present,the measurements indicate degeneratively n-doped material and show that good Ga:As ratios and low levels (ca. 1 ppm) of impurities are present. Growth rates:- 1.0 mm/hour.
INTRODUCTION Group III/V semiconductors have received much attention due to their usefulness in high speed digital circuits, microwave devices, and optoelectronics [1-26] . Several techniques have been employed for the preparation of thin films of these materials, including organometallic chemical vapor deposition
Mat. Res. Soc. Symp. Proc. Vol. 131. t1989 Materials Research Society
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(OMCVD) and molecular beam epitaxy (MBE) . The OMCVD method is often preferred for larger scale processes and typically involves the reaction of a group III trialkyl such as Me3 Ga, with a group V hydride such as AsH 3 or PH 3 at elevated temperatures (600-
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