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Pulsed-Laser-Assisted Molecular Beam Epitaxy

IP.com Disclosure Number: IPCOM000042382D
Original Publication Date: 1984-May-01
Included in the Prior Art Database: 2005-Feb-03
Document File: 1 page(s) / 13K

Publishing Venue

IBM

Related People

Elsner, G: AUTHOR [+4]

Abstract

It is proposed that molecular beam epitaxy (MBE) be preferably performed at low bulk substrate temperatures and that the surface mobility of the atoms or molecules, needed for structuring a perfect epitaxial layer, be ensured by selective irradiation with a pulsed laser. The MBE process is used where very thin monocrystalline solid-state films of a very high quality (crystal perfect) are required, such as during the production of GaAs transistors. This generally necessitates high substrate temperatures (> 500ŒC, for example, for GaAs) which ensure an adequate surface mobility of the molecules or atoms of the molecular beam incident upon the substrate surface. Frequently, however, low substrate temperatures are desirable for preventing chemical reactions, the melting of alloys or the outdiffusion of impurities.

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Pulsed-Laser-Assisted Molecular Beam Epitaxy

It is proposed that molecular beam epitaxy (MBE) be preferably performed at low bulk substrate temperatures and that the surface mobility of the atoms or molecules, needed for structuring a perfect epitaxial layer, be ensured by selective irradiation with a pulsed laser. The MBE process is used where very thin monocrystalline solid-state films of a very high quality (crystal perfect) are required, such as during the production of GaAs transistors. This generally necessitates high substrate temperatures (> 500OEC, for example, for GaAs) which ensure an adequate surface mobility of the molecules or atoms of the molecular beam incident upon the substrate surface. Frequently, however, low substrate temperatures are desirable for preventing chemical reactions, the melting of alloys or the outdiffusion of impurities. For GaAs, epitaxial layers of adequate quality could be obtained at temperatures of less than 500OE only by a simultaneous drastic reduction of the growth rate (0.02 mm/h at 380 C). This, however, increases the processing time required to more than 10 hours, which is intolerable from a production standpoint. It is proposed that MBE be used at low substrate temperatures (e.g., Ts 20OEC). The energy or the surface mobility of the molecular beam atoms, incident upon the substrate surface, required for structuring a perfect crystal, is provided by simultaneous selective irradiation with a pulsed laser. For MBE, the activating energies for the surface migration of atoms are about 0.1 to 3 eV. The method used for this purpose will be referred to below as PLAMBE (Pulsed-Laser-Assisted MBE). For growing thin GaAs epitaxial layers on GaAs substrates, a ruby laser with a wavelength g = 694 nm is used, whose pulse frequency is variable between 0 to 1 kHz by operating...