Metalorganic Chemical Vapor Deposition Of InSb Using Tri-Neopentylindium

Metalorganic chemical vapor deposition of InSb using tri-neopentylindiumJ. C. Chen, W. K. Chen , Pao-Lo Liu Department of Electrical and Computer Engineeringand J. Maloney, 0. T. Beachley, Jr.Department of ChemistryState University of New York at Buffalo Amherst, New York 14260ABSTRACTThe metalorganic chemical vapor deposition (MOCVD) of InSb using tri-neopentylindium ) is reported. The newly synthesized InNp^ has several advantages, e.g., easy to prepare, easy to purify, and non-pyrophoric, over the commonly used tri-ethylindium (TEIn) and tri-methylindium (TMIn) . We report the MOCVD growth of InSb using InNp^. The InSb films were examined by double crystal x-ray diffraction, scanning electron microscope (SEM) , and x-ray energy dispersive analysis. The results indicate that the deposited InSb films are stoichiometric and single crystal. The crystal quality and surface morphology are comparable to similar films grown from TMIn.1. INTRODUCTIONLimited metalorganic sources of In are available. The commonly used tri-ethylindium (TEIn) and tri-methylindium (TMIn) are very expensive because they are neither easy to synthesize nor to purify. In addition, processes through which they are synthesized are quite hazardous. Ideal MOCVD sources shall be readily synthesizable, easy to purify, have adequate vapor pressure near room temperature, and shall be highly stable. We have synthesized a new In-source, Tri-Neopentylindium (InNpg), in our chemistry laboratory. The neopentyl group is sufficiently large that the ether adduct formation can be effectively suppressed. It can also be easily purified by sublimation at 30°C. It is a solid at room temperature and is non-pyrophoric. The volatility is adequate, e. g., a vapor pressure of 2 torr can be obtained at 55°C. By using the Grignard route for synthesis, a yield of 93$ has been obtained.InSb has the highest electron mobility among the III-V semiconductor materials.'' Therefore, at low temperatures, InSb devices are expected to outperform Si or GaAs devices. Moreover, InSb detectors have many applications in the infrared due to its narrow bandgap. Recently, the InSb/CdTe material system has attracted much attention. Their lattice constants are quite close (Aa/a * In this paper, we present the result of MOCVD-grown InSb using the newly synthesized InNp-^. Comparison to films grown from TMIn is also discussed.2. EXPERIMENTAL_PROCEDURES 2.1 Synthesis ofThe molecular structure of InNpo is shown below:Np H CHoI II In - Np Np: - C - C -CH3Np ' H CHoThe synthesis of InNp^ is conducted as follows: a flask charged with 29.1 g (58.3 mmol) of Inl3 dissolved in 100mL of dry diethyl ether (from Na/benzophenone) , was fitted with a condenser, magnetic stir bar and a pressure equalizing funnel. The grease used on all the joints of the apparatus throughout the preparation of InNp-^ was a 40/60 ratio of N and T Apiezon grease. Since the process is sensitive to oxygen and water, it was carried out in an argon ambient. Approximately 80 mL of a solution containing 0.232 mol of neopentyl magnesium chloride in diethyl ether ( previously prepared from purified neopentyl chloride and magnesium turnings ) was transferred to an addition funnel. This Grignard reagent was then added to the Inlo solution over a period of 20 minutes. After the addition was complete, the reaction mixture was stirred at room temperature for 18 hours. The condenser and the addition funnel were then replaced by a stopper and a 1 Teflon valve adapter. The diethyl ether was removed by vacuum distillation at room temperature. The crude product, a