US4376659A
Expired / Lapsed
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Process for forming semiconductor alloys having a desired bandgap
Assignee: Raytheon Co
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Filing: 1981-08-13
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Granted: 1983-03-15
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Expires: 2001-08-13
Abstract
Abstract An epitaxial layer of a narrow-gap semiconductor is deposited on a substrate comprising a wider-gap semiconductor. The opposite surface of the substrate is then illuminated with light pulses at a wavelength corresponding to the desired bandgap of the resulting material. Each pulse causes localized heating where it first encounters a material having a sufficiently narrow bandgap to be an absorber at the wavelength of illumination. This localized heating will then cause interdiffusion, producing a layer of semiconductor alloy having a bandgap intermediate between the bandgaps of the two starting materials. Repetition of this step will have the effect of moving the region of localized absorption away from the original location, and toward the film/air interface. Since the desired end product composition will be transparent to the illumination applied, the process is inherently self-limiting. By appropriately selecting the wavelength of illumination applied, variously proportioned semiconductor compositions may be obtained, so that the bandgap of the resulting material may be arbitrarily selected to have any desired value between the bandgaps of the two starting materials. No surface damage is caused by this technique.
Inventors
- 👤 Carlos A. Castro
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 16:18
CPC Classifications
C; C30; C30B; C30B33/00; C30B1/00; C30B1/10; C30B29/00; C30B29/10; C30B29/40; H; H10; H10F; H10F71/00; H10F71/125; H10F71/1253; H10F71/127; H10F71/1272; Y; Y02; Y02E; Y02E10/00; Y02E10/50; Y02E10/544; Y10; Y10S; Y10S148/00; Y10S148/084
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
114 words
A process for forming a semiconductor alloy having a desired bandgap, comprising the steps of: providing a semiconductor substrate comprising a first material, said first material having a bandgap wider than said desired bandgap and also being transparent to light at a wavelength corresponding to said desired bandgap; depositing on said substrate a layer of a second material, said second material not being metallic and comprising a bandgap which is smaller than said desired bandgap; and illuminating said substrate, from the surface of said substrate on which said layer of said second material was not deposited, with light having a wavelength which is at least as long as that corresponding to said desired bandgap.
Claim 2
Dependent Claim
114 words
A process for forming a semiconductor alloy having a desired bandgap, comprising the steps of: providing a semiconductor substrate comprising a first material, said first material having a bandgap wider than said desired bandgap and also being transparent to light at a wavelength corresponding to said desired bandgap; depositing on said substrate a layer of a second material, said second material not being metallic and comprising a bandgap which is smaller than said desired bandgap; and illuminating said substrate, from the surface of said substrate on which said layer of said second material was not deposited, with light having a wavelength which is at least as long as that corresponding to said desired bandgap.
Claim 3
Dependent Claim
12 words
The process of claim 1, wherein said second material comprises a semimetal.
Claim 4
Dependent Claim
51 words
The process of claim 1, further comprising the step of: illuminating said substrate again, at a second wavelength which is shorter than the wavelength of said first illumination but is not shorter than the wavelength corresponding to said desired bandgap, said second illuminating step being performed after said first illuminating step.
Claim 5
Dependent Claim
19 words
The process of claim 3, wherein said second illuminating step is applied only to selected portions of said substrate.
Claim 6
Dependent Claim
80 words
The process of claim 3, further comprising a third illuminating step, wherein said third illuminating step is applied after said first and second illuminating steps, and uses light of a wavelength which is shorter than the wavelength of said second illuminating step but is not shorter than the wavelength corresponding to said desired bandgap, said third illuminating step only being applied to selected areas within those portions of said substrate which have previously been illuminated by said second illuminating step.
Claim 7
Dependent Claim
26 words
The process of claim 3 or 4, wherein said second illuminating step applies a wavelength which is approximately equal to that corresponding to said desired bandgap.
Claim 8
Dependent Claim
12 words
The process of claim 6, wherein said second material comprises a semimetal.
Claim 9
Dependent Claim
19 words
The process of claim 6, wherein said first and second materials each consist essentially of a respective III-V compound.
Claim 10
Dependent Claim
21 words
The process of claim 8, wherein said first material consists essentially of AlAs, and said second material consists essentially of GaAs.
Claim 11
Dependent Claim
21 words
The process of claim 8, wherein said first material consists essentially of GaAs, and said second material consists essentially of InAs.
Claim 12
Dependent Claim
18 words
The process of claim 6, wherein said first and second materials each consist essentially of respective II-VI compounds.
Claim 13
Dependent Claim
26 words
The process of claim 1, wherein said illuminating step applies light having a wave length which is approximately equal to that corresponding to said desired bandgap.
Claim 14
Dependent Claim
33 words
The process of claim 1, wherein said illuminating step applies a wave length which is approximately equal to that corresponding to said desired band gap, and wherein said second material comprises a semimetal.
Claim 15
Dependent Claim
19 words
The process of claim 12, wherein said first and second materials each consist essentially of a respective III-V compound.
Claim 16
Dependent Claim
21 words
The process of claim 14, wherein said first material consists essentially of aluminum arsenide, and said material consists essentially gallium arsenide.
Claim 17
Dependent Claim
23 words
The process of claim 14, wherein said first material consists essentially of gallium arsenide, and said second material consists essentially of indium arsenide.
Claim 18
Dependent Claim
18 words
The process of claim 12, wherein said first and second materials each consist essentially of respective II-IV compounds.
Claim 19
Dependent Claim
99 words
The process of claim 1, further comprising the additional step of: after said first illuminating step, repeatedly illuminating said substrate from the surface of said substrate on which said layer of said second material was not deposited, with light having a wave length which is at least as long as that corresponding to said desired band gap, said additional illuminating steps being performed repeatedly until said layer of said second material has been mixed with said first material to provide a mixed material having approximately said desired band gap at the exposed surface of said layer of second material.
Claim 20
Dependent Claim
22 words
The process of claim 1, 3, 4, or 16, wherein said layer of said second material is much thinner than said substrate.
Claim 21
Dependent Claim
16 words
The process of claim 19, wherein said layer of said second material is an epitaxial layer.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-03-14 | 1986-09-13 | 1987-03-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-03-14 | 1990-09-13 | 1991-03-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-03-14 | 1994-09-13 | 1995-03-15 | $7700.00 | Window Closed / Lapsed |