The Use of Novel Organometallic Sources in Metal Organic Chemical Vapor Deposition (MOCVD)
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THE USE OF NOVEL ORGANOMETALLIC SOURCES IN METAL ORGANIC CHEMICAL VAPOR DEPOSITION (MOCVD) R. M. Biefeld, Sandia National Laboratories, Albuquerque, NM 87185
ABSTRACT In metal organic chemical vapor deposition (MOCVD), the most commonly used sources are the trimethyls of Al, Ga, In, and Sb, and PH3 and AsH3. New organometallic sources are being developed as the understanding of the deposition process improves and allows for the determination of the effects of source type and growth condition on the properties of the grown films. These new sources are safer and allow for the growth of higher purity materials using more favorable growth conditions. InSb and AlSb prepared using these trimethyl-sources are not of high enough quality to be used in many current device applications. Alternate organometallic Sb sources are being investigated to improve the materials characteristics of InSb grown by MOCVD. InSb grown using trimethylindium (TMIn) and trimethylantimony (TMSb) or triethylantimony (TESb) yielded similar quality materials under similar growth conditions. InSb grown using triethylindium (TEIn) and TESb under similar growth conditions yielded very poor quality n-type material. Three new organometallic Sb sources, triisopropylantimony (TIPSb), tris(dimethylamino)antimony (TDMASb), and tertiarybutyldimethylantimony (TBDMSb) are being investigated. The growth of InSb using TIPSb, TDMASb, or TBDMSb and TMIn was investigated over a temperature range of 350 to 475 oc. InSb grown from TDMASb had similar properties to InSb grown from TMIn and TMSb when using a similar temperature and V/Ill ratio range. The growth rates of InSb using TMIn and either TIPSb or TBDMSb at temperatures 450 oC at atmospheric pressure and all V/Ill ratios. P-type InSb also resulted for the growth of InSb from TBDMSb at 400 oC, 660 torr and a V/Ill ratio of 2.0. As discussed in the introduction above, the growth of p-type InSb for TŽ 400 oC is probably related to the presence of an intrinsic defect [10,12,16]. Figure 3 shows a plot of mobility vs. carrier concentration of n-type InSb grown from TIPSb and TMIn. The values are somewhat lower than the mobilities reported for bulk n-type InSb as indicated in Figure 3 [22]. This could be due to the presence of a compensated, background impurity, an intrinsic defect, or the fact that the samples were all rough and some were relatively thin. It should be mentioned that the carrier concentration decreased as the sample thickness increased. This decrease in carrier concentration indicates that there may have been
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N-Type InSb 77 K Hall Data •____ForDifferent Sb Sources
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Carrier Concentration(cm"3)
Figure 3. Mobility versus carrier concentration plot for n-type InSb grown using the sources as indicated by the inset. The literature values were taken from reference 22.
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