AVS 45th International Symposium
    Electronic Materials and Processing Division Thursday Sessions
       Session EM-ThM

Paper EM-ThM6
Variable Substrate Temperature for Precise Growth of II-VI Interfaces

Thursday, November 5, 1998, 10:00 am, Room 316

Session: Compound Semiconductor Surface Chemistry
Presenter: Y. Luo, Columbia University
Authors: Y. Luo, Columbia University
M. Han, Columbia University
J.E. Moryl, Columbia University
R.M. Osgood, Jr., Columbia University
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This paper describes the use of variable substrate temperature for the controlled growth of compound semiconductor hetero-interfaces. The investigation uses UHV surface probes to show that choice of surface temperature and temperature ramping during each half of bilayer growth, can lead to a precisely controlled interface composition. The emphasis on the investigation thus far is controlled interface abruptness, composition and crystallinity. The experiment uses sequential dosing of a ZnSe(100) substrate with dimethylcadmium and H@sub 2@S, respectively, in a UHV system. The substrate temperature is controlled by a temperature controller system and may be raised from 100K to 700K at 4K/sec. In situ surface analysis is accomplished with TPD, AES, LEIS and LEED. The experiments showed that, when DMCd was dosed onto a well ordered c(2x2) ZnSe substrate, the composition of surface growth varied dramatically with the substrate temperature. AES and TPD measurements show that this variation is directly dependent on the chemical interaction of the organic ligands at the surface at differing substrate temperatures. For example, within the temperature range from 250 K to 370 K, the Cd growth mode can change from a simple 0.5 monolayer Cd insertion, to a self-terminating one monolayer deposition or even a thick multilayer of Cd with significant Zn depletion near the interface. In the presence of a hydrogen sulfide flux the percentage of sulfur growth at the surface is directly dependent on the surface-coverage of existing methyl groups due to previous dosing of DMCd. Finally we have found that by selection of dosing temperature and the following temperature ramping one can accurately manipulate the interface compsition on a monolayer scale, e.g. a mixture of a half monolayer Zn and a half monolayer Cd, or an abrupt full monolayer of Cd or intermediate layers of Zn@sub 1-x@Cd@sub x@Se@sub 1-y@S@sub y@.