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Vapor Phase Epitaxial Deposition Process for Forming Superlattice Structure

IP.com Disclosure Number: IPCOM000075037D
Original Publication Date: 1971-Jul-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 4 page(s) / 38K

Publishing Venue

IBM

Related People

Blakeslee, AE: AUTHOR

Abstract

Described is a process and apparatus for forming epitaxial superlattice structures, where the band-gap energy of the superlattice structure can be varied. From a maximum to a minimum value within a period as small as 100 Angstroms.

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Vapor Phase Epitaxial Deposition Process for Forming Superlattice Structure

Described is a process and apparatus for forming epitaxial superlattice structures, where the band-gap energy of the superlattice structure can be varied. From a maximum to a minimum value within a period as small as 100 Angstroms.

Refer to the figure, there is shown representative apparatus for forming a ternary superlattice, i.e., a GaAs(1-x)P(x) superlattice, from GaCl, AsH(3), and PH(3), all in a carrier gas, e.g., hydrogen. The main elements are an n-1 component stream, e.g. GaCl + AsH(3), a mixing chamber 21, a pulsing chamber 34 (which receives the n-1 component stream from the mixing chamber) wherein the nth component, i.e., PH(3), is injected into the n-1 component stream by the pulsing means via an injection tube 31, and a deposition chamber 35 wherein the superlattice is deposited.

AsH(3) in hydrogen is introduced into the mixing chamber 21 via line 22. Although GaCl can be directly introduced into the system, in the present embodiment GaCl is actually formed in the mixing chamber 21. This is accomplished by introducing a stream of hydrogen chloride in the carrier gas via line 23, into a gallium reservoir 24 in the interior of mixing chamber 21. Vents 25 are provided in the top of the gallium reservoir 24 so that the hydrogen chloride in the carrier gas entering via line 23 is contacted with the gallium 26 in the gallium reservoir 24, reacted, and passed into the mixing chamber 21 via vents 25, where the GaCl formed in the interior of the gallium reservoir 24 is mixed with the AsH(3). Appropriate heating coils 27 are provided around the exterior of the mixing chamber 21 to provide the temperature required for the HCl-Ga reaction.

The mixing chamber 21 basically insures that the PH(3) is pulsed into a homogenous mixture of GaCl and AsH(3). Contrary to prior deposition processes, to achieve the type of periodic structure heretofore described, it is necessary to maintain the n-1 component stream, i.e., the GaCl and AsH(3), separate from the nth component, i.e., the PH(3), until a point just prior to the substrate upon which deposition is desired.

In the present embodiment, this is done by injecting pulses of PH(3) in a carrier gas, under certain very critical conditions, into the GaCl AsH(3) mixture at a point subsequent to the first mixing chamber 21, but prior to the substrate 28 to form alternate bursts of GaCl-AsH(3) separated by bursts of GaCl-AsH(3)-PH(3). The critical feature here is to control interdiffusion of adjacent pulses and bursts. In this apparatus, for a ternary material, the PH(3) is injected into the GaCl- AsH(3) mixture via PH(3) injection tube 31, i.e., PH(3) from line 29 is rapidly injected, on a periodic basis, into flowing carrier gas in line 30, whereafter the composite stream is fed into the PH(3) injection tube 31. Pulsing of the PH(3) is accomplished, by alternately feeding PH(3) from line 29 into the carrier gas in line...