US4012242A
Expired / Lapsed
US
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Liquid epitaxy technique
Assignee: Infineon Technologies Americas Corp
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Filing: 1973-11-14
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Granted: 1977-03-15
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Expires: 1993-11-14
Abstract
Abstract In a preferred embodiment, a technique and associated apparatus for producing heteroepitaxial semi-conductor junctions preferably for Group III-V compounds in an improved liquid-solid transport method, placing a prescribed doped "limited-volume" melt directly upon a host substrate and treating these in a very precisely controlled heating-cooling schedule and associated equipment whereby the substrate is melt-back to a prescribed degree, and then very carefully recrystallized in a crystal layer of the desired volume and stoichiometry (determined by the melt-volume). This is preferably effected by transport through a vertical temperature gradient; with the seed crystal (or melt) used as a saturation source to effect melt-back and such that the doping at the junction is effected by substrate dopant and melt dopant; the effect will be to enhance regrowth of a perfect epitaxial junction already formed, like a junction formed from a gallium, unsaturated aluminum-zinc melt on a gallium arsenide substrate, the substrate crystal serving as a saturation source. Preferably the Peltier cooling of the liquid-seed interface is used for fine control of the cooling and interface temperature, resulting in very low dislocation counts and high radiation efficiency and speed for junctions used as light emitters.
Inventors
- 👤 Herbert F. Matare
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 14:18
CPC Classifications
H; H10; H10P; H10P14/00; H10P14/20; H10P14/26; H10P14/263; C; C30; C30B; C30B13/00; C30B13/02; C30B19/00; C30B19/10; C30B19/103; C30B19/12; H10P14/32; H10P14/3242; H10P14/3244; H10P14/3254; H10P14/34; H10P14/3402; H10P14/3414; H10P14/3416; H10P14/3418; H10P14/3421; H10P14/3438; H10P14/3441; Y; Y10; Y10S; Y10S148/00; Y10S148/071; Y10S148/072; Y10S148/108; Y10S438/00; Y10S438/936; Y10S438/955
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
184 words
A method for producing a superior heteroepitaxial semiconductor junction comprising superposing a prescribed doped limited volume unsaturated melt directly upon a host substrate and subjecting the resulting material to a four phase thermal cycle adapted to provide a moving external thermal gradient and a prescribed internal fixed thermal gradiant across the melt-substrate interface; the first phase comprising heating to a temperature such that the substrate is melted back to a prescribed degree and with prescribed diffusion, the dissolved substrate saturating the melt; the second phase comprising cooling at a rate adapted to rapidly arrest melting back of the substrate and terminate upward thermal momentum with attendant supersaturation; the third phase comprising cooling at a rate of 0.1°-1.0° C per minute to initiate slow recrystallization and diffusion; the fourth phase comprising cooling at a rate of 2°-5° C per minute to recrystallize the entire melt-substrate combination; wherein said limited volume is that volume which will be saturated by the substrate during melting back; whereby a graded epitaxial junction of a crystal layer having a prescribed volume and stoichiometry with very low dislocation incidence is obtained.
Claim 2
Independent Claim
184 words
A method for producing a superior heteroepitaxial semiconductor junction comprising superposing a prescribed doped limited volume unsaturated melt directly upon a host substrate and subjecting the resulting material to a four phase thermal cycle adapted to provide a moving external thermal gradient and a prescribed internal fixed thermal gradiant across the melt-substrate interface; the first phase comprising heating to a temperature such that the substrate is melted back to a prescribed degree and with prescribed diffusion, the dissolved substrate saturating the melt; the second phase comprising cooling at a rate adapted to rapidly arrest melting back of the substrate and terminate upward thermal momentum with attendant supersaturation; the third phase comprising cooling at a rate of 0.1°-1.0° C per minute to initiate slow recrystallization and diffusion; the fourth phase comprising cooling at a rate of 2°-5° C per minute to recrystallize the entire melt-substrate combination; wherein said limited volume is that volume which will be saturated by the substrate during melting back; whereby a graded epitaxial junction of a crystal layer having a prescribed volume and stoichiometry with very low dislocation incidence is obtained.
Claim 3
Dependent Claim
39 words
The method as recited in claim 1 wherein the melt and substrate are brought operatively adjacent a prescribed thermal gradient and moved relative thereto at a prescribed rate adapted to effect the said melt-back and recrystallization and imparting distribution.
Claim 4
Dependent Claim
26 words
The method as recited in claim 1 wherein the said heat cycling fixed internal gradient is effected at least in part by a "Peltier effect" cooling.
Claim 5
Dependent Claim
39 words
The method claim 1 wherein said substrate is a wafer, wherein a prescribed vertical temperature gradient is impressed on the melt-substrate, and wherein said melt-substrate is vertically moved through said temperature gradient to effect said four phase thermal cycle.
Claim 6
Dependent Claim
50 words
A method according to claim 1 wherein said melt comprises gallium, aluminum and zinc, and wherein the melt-substrate is subjected to a moving temperature gradient together with supplemental Peltier cooling being provided such that current is supplied to the melt-substrate interface in a direction to cool the interface after melt-back.
Claim 7
Dependent Claim
28 words
The method of claim 1 wherein the melt is selected from the group consisting of Group III/V compounds and ternary compounds thereof, Group II/VI compounds, and mixtures thereof.
Claim 8
Dependent Claim
52 words
The method of claim 6 wherein the melt comprises gallium, aluminum and zinc, and the substrate comprises gallium arsenide and silicon dopant, and wherein the concentration of aluminum varies continuously across the junction in graded fashion with the silicon concentration varying inversely and the zinc concentration in parallel to the aluminum concentration.
Claim 9
Dependent Claim
22 words
The method of claim 6 wherein said Group III/V compound is selected from the group consisting of (GaAl)As, (GaIn)As, (GaIn)P, and Ga(AsP).
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-03-14 | 1980-09-13 | 1981-03-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-03-14 | 1984-09-13 | 1985-03-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-03-14 | 1988-09-13 | 1989-03-15 | $7700.00 | Window Closed / Lapsed |