US3915765A
Expired / Lapsed
US
⏱️ 0.0 years remaining
MBE technique for fabricating semiconductor devices having low series resistance
Assignee: AT&T Inc
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Filing: 1973-06-25
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Granted: 1975-10-28
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Expires: 1993-06-25
Abstract
Abstract In order to fabricate by MBE semiconductor devices, such as junction lasers and light modulators or varactor and impatt diodes, having relatively low series resistance one or more of the following three steps are executed: (1) on the substrate a high conductivity buffer layer is first grown having the same conductivity-type as the substrate; (2) beginning with the high conductivity layer and until all semiconductor layers of the device are fabricated, the growth process is made to be continuous; and (3) the substrate is heated just prior to the growth of the high conductivity layer and under excess pressure of any element in the substrate which has a relatively high vaporization pressure and which tends to evaporate from the heated substrate. Preferably all three steps are performed.
Inventors
- 👤 Alfred Yi Cho
- 👤 Franz Karl Reinhart
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-02 13:48
CPC Classifications
H; H10; H10P; H10P14/00; H10P14/20; H10P14/29; H10P14/2901; H10P14/2907; H10P14/2909; H10P14/22; H10P14/2911; H10P14/2921; H10P14/32; H10P14/3202; H10P14/3214; H10P14/3221; H10P14/34; H10P14/3402; H10P14/3414; H10P14/3421; H10P14/3424; H10P14/3428; H10P14/3438; H10P14/3441; H10P14/3442; H10P14/3444; H10P14/36; H10P14/3602; Y; Y10; Y10S; Y10S148/00; Y10S148/007; Y10S148/017; Y10S148/018; Y10S148/02; Y10S148/064; Y10S148/065; Y10S148/072; Y10S148/139; Y10S148/15; Y10S148/169; Y10S438/00; Y10S438/909; Y10S438/914; Y10S438/916; Y10S438/925
Claims Analysis
Total Claims: 28
Claim 1
Independent Claim
185 words
A METHOD FOR EPITAXIAL GROWING UPON A SUBSTRATE A SEMICONDUCTOR DEVICE INCLUDING AT LEAST ONE EPITAXIAL LAYER OF A MATERIAL HAVING A COMPOSITION AB, WHERE A IS AT LEAST ONE GROUP III(A) ELEMENT HAVING A LOW VAPOR PRESSURE AND B IS AT LEAST ONE GROUP V(A) ELEMENT HAVING A RELATIVELY HIGHER VAPOR PRESSURE, COMPRISING THE STEPS OF: A. REDUCING THE BACKGROUND PRESSURE TO A SUBATMOSPHERIC PRESSURE, B. PPREHEATING SAID SUBSTRATE TO A PREDETERMINED TEMPERATURE, C. DIRECTING AT LEAST ONE MOLECULAR BEAM COMPRISING A, B AND A DOPANT AT SAID SUBSTRATE FOR A TIME PERIOD SUFFICIENT TO EFFECT GROWTH OF SAID AT LEAST ONE EPITAXIAL LAYER OF THE DESIRED THICKNESS, SAID PREDETERMINED TEMPERATURE BEING EFFECTIVE TO ALLOW ATOMS IMPINGING THEREON TO MIGRATE TO SURFACE SITES TO FORM SAID AT LEAST ONE EPITAXIAL LAYER AND EFFECTIVE TO PRODUCE CONGRUENT EVAPORATION OF SAID A ELEMENTS AND SAID B ELEMENTS, D. MAINTAINING THE RELATIVE PROPOTIONS OF THE CONSTITUENTS OF SAID AT LEAST ONE MOLECULAR BEAM SO THAT AT THE GROWTH SURFACE THERE IS AN EXCESS OF SAID B ELENMENTS WITH RESPECT TO SAID A ELEMENTS, AND CHARACTERIZED IN THAT:
Claim 2
Independent Claim
185 words
A METHOD FOR EPITAXIAL GROWING UPON A SUBSTRATE A SEMICONDUCTOR DEVICE INCLUDING AT LEAST ONE EPITAXIAL LAYER OF A MATERIAL HAVING A COMPOSITION AB, WHERE A IS AT LEAST ONE GROUP III(A) ELEMENT HAVING A LOW VAPOR PRESSURE AND B IS AT LEAST ONE GROUP V(A) ELEMENT HAVING A RELATIVELY HIGHER VAPOR PRESSURE, COMPRISING THE STEPS OF: A. REDUCING THE BACKGROUND PRESSURE TO A SUBATMOSPHERIC PRESSURE, B. PPREHEATING SAID SUBSTRATE TO A PREDETERMINED TEMPERATURE, C. DIRECTING AT LEAST ONE MOLECULAR BEAM COMPRISING A, B AND A DOPANT AT SAID SUBSTRATE FOR A TIME PERIOD SUFFICIENT TO EFFECT GROWTH OF SAID AT LEAST ONE EPITAXIAL LAYER OF THE DESIRED THICKNESS, SAID PREDETERMINED TEMPERATURE BEING EFFECTIVE TO ALLOW ATOMS IMPINGING THEREON TO MIGRATE TO SURFACE SITES TO FORM SAID AT LEAST ONE EPITAXIAL LAYER AND EFFECTIVE TO PRODUCE CONGRUENT EVAPORATION OF SAID A ELEMENTS AND SAID B ELEMENTS, D. MAINTAINING THE RELATIVE PROPOTIONS OF THE CONSTITUENTS OF SAID AT LEAST ONE MOLECULAR BEAM SO THAT AT THE GROWTH SURFACE THERE IS AN EXCESS OF SAID B ELENMENTS WITH RESPECT TO SAID A ELEMENTS, AND CHARACTERIZED IN THAT:
Claim 3
Dependent Claim
33 words
PRIOR TO STEP (C) A FIRST MOLECULAR BEAM(S) IS DIRECTED UPON SAID SUBSTRATE TO EFFECT GROWTH THEREON OF A HIGH CONDUCTIVITY BUFFER LAYER OF THE SAME CONDUCTIVITY TYPE AND MATERIAL AS THE SUBSTRATE,
Claim 4
Dependent Claim
33 words
PRIOR TO STEP (C) A FIRST MOLECULAR BEAM(S) IS DIRECTED UPON SAID SUBSTRATE TO EFFECT GROWTH THEREON OF A HIGH CONDUCTIVITY BUFFER LAYER OF THE SAME CONDUCTIVITY TYPE AND MATERIAL AS THE SUBSTRATE,
Claim 5
Dependent Claim
47 words
BEGINNING WITH STEP (1) AND UNTIL SAID BUFFER LAYER AND ALL OF SAID AT LEAST ONE EPITAXIAAL LAYERS ARE GROWN, AT LEAST ONE BEAM INCLUDING AN ELEMENT OF A AND B AT ALL TIMES IMPINGES ON THE GROWTH SURFACE SO THAT SAID GROWTH PROCESS IS CONTINUOUS, AND
Claim 6
Dependent Claim
47 words
BEGINNING WITH STEP (1) AND UNTIL SAID BUFFER LAYER AND ALL OF SAID AT LEAST ONE EPITAXIAAL LAYERS ARE GROWN, AT LEAST ONE BEAM INCLUDING AN ELEMENT OF A AND B AT ALL TIMES IMPINGES ON THE GROWTH SURFACE SO THAT SAID GROWTH PROCESS IS CONTINUOUS, AND
Claim 7
Dependent Claim
22 words
The method of claim 1 wherein said substrate is preheated to a temperature in the range of about 450 to 650* C.
Claim 8
Dependent Claim
47 words
beginning with step (1) and until said buffer layer and all of said at least one epitaxial layers are grown, at least one beam including an element of A and B at all times impinges on the growth surface so that said growth process is continuous; and
Claim 9
Dependent Claim
47 words
beginning with step (1) and until said buffer layer and all of said at least one epitaxial layers are grown, at least one beam including an element of A and B at all times impinges on the growth surface so that said growth process is continuous; and
Claim 10
Dependent Claim
17 words
DURING STEP (B) SAID PREHEATING TAKES PLACE IN A GASEOUS ATMOSPHERE WHICH INCLUDES AN ELEMENT OF B.
Claim 11
Dependent Claim
17 words
DURING STEP (B) SAID PREHEATING TAKES PLACE IN A GASEOUS ATMOSPHERE WHICH INCLUDES AN ELEMENT OF B.
Claim 12
Dependent Claim
17 words
during step (b) said preheating takes place in a gaseous atmosphere which includes an element of B.
Claim 13
Dependent Claim
17 words
during step (b) said preheating takes place in a gaseous atmosphere which includes an element of B.
Claim 14
Dependent Claim
24 words
The method of claim 2 wherein said at least one epitaxial layer comprises AlxGa1 xAs, 0 < or = x < or = 1.
Claim 15
Dependent Claim
31 words
The method of claim 2 wherein the substrate comprises GaAs and said preheating step (b) occurs just prior to step (1) and under condition of excess As pressure at said substrate.
Claim 16
Dependent Claim
20 words
The method of claim 4 wherein both said substrate and said buffer layer have net carrier concentrations of about 1018/cm3.
Claim 17
Dependent Claim
11 words
The method of claim 5 wherein said buffer layer comprises GaAs.
Claim 18
Dependent Claim
75 words
A method of fabricating a semiconductor device comprising the steps of: a. performing the steps of claim 6 to fabricate a high conductivity GaAs buffer layer on said GaAs substrate and a relatively lower conductivity active layer on said buffer layer; and b. programming in time the intensity of the dopant in said at least one molecular beam so that a predetermined profile of net carrier concentration Delta N is produced in said active layer.
Claim 19
Dependent Claim
58 words
The method of claim 7 for fabricating a hyperabrupt varactor wherein the intensity of the dopant is programmed so that a profile conforming approximately to the following relationship is formed in said active layer: Delta N kx 1.5 where k is a constant, and x is the distance into said active layer as measured from said buffer layer.
Claim 20
Dependent Claim
28 words
The method of claim 8 including the steps of c. forming an ohmic contact to said substrate; and d. forming a Schottky barrier contact to said active layer.
Claim 21
Dependent Claim
22 words
The method of claim 8 wherein Delta N in said active layer ranges between approximately 1 X 1017/cm3 and 4 X 1015/cm3.
Claim 22
Dependent Claim
17 words
The method of claim 9 wherein said substrate, buffer layer and active layer all have n-type conductivity.
Claim 23
Dependent Claim
46 words
The method of claim 7 wherein the intensity of the dopant is programmed so that said profile has a region in which the net carrier concentration decreases from about 1 X 1017/cm3 to about 7 X 1015/cm3 over a distance on the order of 5000 Angstroms.
Claim 24
Dependent Claim
34 words
The method of claim 12 for fabricating a snap varactor including the additional steps of: c. forming an ohmic contact to said substrate and d. forming a Schottky barrier contact to said active layer.
Claim 25
Independent Claim
244 words
A method for epitaxially growing upon a GaAs substrate surface a semiconductor device including at least one epitaxial layer of a Group III(a)-V(a) compound material comprising the steps of: a. reducing the background pressure to at least 10 8 Torr approximately; b. just prior to step (c), preheating the substrate to a temperature in the range of about 450 to 650* C. under a condition of excess As pressure at said surface; c. directing at least one first molecular beam comprising Ga, As and a dopant upon said surface to effect growth thereon of a high conductivity GaAs buffer layer having a conductivity type the same as that of the substrate; d. directing at least one second molecular beam comprising a Group III(a) element, a Group V(a) element and a dopant upon said buffer layer for a time period sufficient to effect growth of said at least one epitaxial layer of the desired thickness and conductivity type; e. maintaining the relative proportions of the constituents of said first and second molecular beams so that at the growth surface there is an excess of said group V(a) elements with respect to said Group III(a) elements; and f. beginning with said step (c) and until said buffer layer and all of said at least one epitaxial layers are grown, maintaining at least one beam including an element of A and B at all times impinging on the growth surface so that said growth process is continuous.
Claim 26
Independent Claim
244 words
A method for epitaxially growing upon a GaAs substrate surface a semiconductor device including at least one epitaxial layer of a Group III(a)-V(a) compound material comprising the steps of: a. reducing the background pressure to at least 10 8 Torr approximately; b. just prior to step (c), preheating the substrate to a temperature in the range of about 450 to 650* C. under a condition of excess As pressure at said surface; c. directing at least one first molecular beam comprising Ga, As and a dopant upon said surface to effect growth thereon of a high conductivity GaAs buffer layer having a conductivity type the same as that of the substrate; d. directing at least one second molecular beam comprising a Group III(a) element, a Group V(a) element and a dopant upon said buffer layer for a time period sufficient to effect growth of said at least one epitaxial layer of the desired thickness and conductivity type; e. maintaining the relative proportions of the constituents of said first and second molecular beams so that at the growth surface there is an excess of said group V(a) elements with respect to said Group III(a) elements; and f. beginning with said step (c) and until said buffer layer and all of said at least one epitaxial layers are grown, maintaining at least one beam including an element of A and B at all times impinging on the growth surface so that said growth process is continuous.
Claim 27
Dependent Claim
42 words
The method of claim 14 wherein said substrate is doped n-Type to a net carrier concentration of about 1018/cm3 and said first molecular beam is effective to produce an n-type GaAs buffer layer doped to a net carrier concentration of about 1018/cm3.
Claim 28
Dependent Claim
31 words
The method of claim 15 wherein said first molecular beam is directed at said substrate for a time period effective to grow said buffer layer about 1 Mu m in thickness.
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) | 1978-10-27 | 1979-04-28 | 1979-10-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-10-27 | 1983-04-28 | 1983-10-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-10-27 | 1987-04-28 | 1987-10-28 | $7700.00 | Window Closed / Lapsed |