US4414066A
Expired / Lapsed
US
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Electrochemical photoetching of compound semiconductors
Assignee: AT&T Inc
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Filing: 1982-09-10
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Granted: 1983-11-08
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Expires: 2002-09-10
Abstract
Abstract A procedure is described for electrochemically photoetching n-type and intrinsic compound semiconductors. The process involves applying a potential to the compound semiconductor while it is in contact with an electrolytic solution and irradiating the surface to be etched with light in a certain energy range. By suitable adjustment in the potential, electrolytic solution composition and light energy, the etch rate is made proportional to the light intensity. By suitable variation in light intensity and light-ray direction, various geometrical features can be made on the surface of the compound semiconductor. For example, a hole with straight sides can be made in the compound semiconductor by use of a light spot and parallel (collimated) light rays. An advantageous application of this process is the fabrication of a photodiode with a hole in the center for use in bidirectional communication systems and to monitor power output for optical communication sources. The advantage of this process is that no damage occurs outside etched hole so that a maximum area of the photodiode remains active for detecting incoming radiation. Another advantage of the process is that etching will stop where the material becomes p-type so that etching can be made to stop automatically at a p/n junction.
Inventors
- 👤 Stephen R. Forrest
- 👤 Paul A. Kohl
- 👤 Richard L. Panock
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:09
CPC Classifications
H; H10; H10P; H10P50/00; H10P50/69; C; C25; C25F; C25F3/00; C25F3/02; C25F3/12; H10P50/20; H10P50/60; H10P50/61; H10P50/617; H10P52/00; H10P95/00; H10P95/70
Claims Analysis
Total Claims: 27
Claim 1
Independent Claim
151 words
A process for fabricating a device comprising at least one intrinsic or n-type compound semiconductor comprising the step of electrochemically photoetching at least part of the surface of the compound semiconductor to produce oxidized species by passing current through the compound semiconductor, an electrolytic solution with conductivity greater than 0.0001 mhos/cm and a cathode characterized in that the step further comprises a. applying a potential to the semiconducting compound which is between the maximum potential of the valence band of the semiconductor compound in the electrolytic solution and the minimum potential of the conduction band of the semiconductor compound in the electrolytic solution; b. illuminating the part of the surface of the compound semiconductor to be etched with radiation of sufficient energy to produce holes in the valence band; c. including in the composition of the electrolytic solution species which remove the oxidized species from the surface of the compound semiconductor.
Claim 2
Dependent Claim
151 words
A process for fabricating a device comprising at least one intrinsic or n-type compound semiconductor comprising the step of electrochemically photoetching at least part of the surface of the compound semiconductor to produce oxidized species by passing current through the compound semiconductor, an electrolytic solution with conductivity greater than 0.0001 mhos/cm and a cathode characterized in that the step further comprises a. applying a potential to the semiconducting compound which is between the maximum potential of the valence band of the semiconductor compound in the electrolytic solution and the minimum potential of the conduction band of the semiconductor compound in the electrolytic solution; b. illuminating the part of the surface of the compound semiconductor to be etched with radiation of sufficient energy to produce holes in the valence band; c. including in the composition of the electrolytic solution species which remove the oxidized species from the surface of the compound semiconductor.
Claim 3
Dependent Claim
15 words
The process of claim 1 in which the compound semiconductor is a III-V compound semiconductor.
Claim 4
Dependent Claim
31 words
The process of claim 2 in which the compound semiconductor is selected from the group consisting of GaP, GaAs, AlAs, AlP, AlSb, InSb, InAs, InP, GaInAs, GaInP, GaInAsP, GaAlP and GaAlAs.
Claim 5
Dependent Claim
15 words
The process of claim 1 in which the compound semiconductor is a II-VI compound semiconductor.
Claim 6
Dependent Claim
20 words
The process of claim 4 in which the compound semiconductor is selected from the group consisting of CdS, CdSe, HgCdTe.
Claim 7
Dependent Claim
30 words
The process of claim 1 in which the compound is n-type InP and the potential of the SCE scale is between -0.5 and +1.0 volts in one molar hydrochloric acid.
Claim 8
Dependent Claim
15 words
The process of claim 6 in which the potential is between -0.1 and +0.5 volts.
Claim 9
Dependent Claim
31 words
The process of claim 1 in which the compound semiconductor is n-type GaAs and the potential is between -0.7 and +1.0 volts on the SCE scale in one molar hydrochloric acid.
Claim 10
Dependent Claim
15 words
The process of claim 8 in which the potential is between -0.4 and +0.4 volts.
Claim 11
Dependent Claim
17 words
The process of claim 1 in which the pH of the electrolytic solution is greater than 9.
Claim 12
Dependent Claim
13 words
The process of claim 10 in which the pH is greater than 11.
Claim 13
Dependent Claim
17 words
The process of claim 1 in which the pH of the electrolytic solution is less than 5.
Claim 14
Dependent Claim
13 words
The process of claim 12 in which the pH is less than 3.
Claim 15
Dependent Claim
23 words
The process of claim 13 in which the electrolytic solution comprises an acid selected from the group consisting of HF, HC1 and HBr.
Claim 16
Dependent Claim
11 words
The process of claim 14 in which the acid is HC1.
Claim 17
Dependent Claim
17 words
The process of claim 14 in which the acid concentration varies from about 0.05 to 10 molar.
Claim 18
Dependent Claim
19 words
The process of claim 16 in which the concentration range of the acid is between 0.2 and 2.0 molar.
Claim 19
Dependent Claim
15 words
The process of claim 1 in which the electrolytic solution contains salts to improve conductivity.
Claim 20
Dependent Claim
12 words
The process of claim 1 in which the compound semiconductor is intrinsic.
Claim 21
Dependent Claim
12 words
The process of claim 1 in which the compound semiconductor is n-type.
Claim 22
Dependent Claim
21 words
The process of claim 20 in which the doping level is between 10 15 and 10 19 atoms per cubic centimeter.
Claim 23
Dependent Claim
22 words
The process of claim 1 in which the energy of the radiation is greater than the band gap of the compound semiconductor.
Claim 24
Dependent Claim
12 words
The process of claim 1 in which the device is a photodiode.
Claim 25
Dependent Claim
35 words
The process of claim 23 in which the photodiode has an n-type InP substrate, with a thin layer of n-type InP then a thin layer of n-type InGaAs and then a layer of p-type InGaAs.
Claim 26
Dependent Claim
45 words
The process of claim 24 in which a hole is photoetched in the center of the photodiode structure n-type layer and intrinsic layer by electrochemical photoetching with a potential of 0.2±0.1 volts on the SCE scale and an electrolytic solution comprising one molar hydrochloric acid.
Claim 27
Dependent Claim
16 words
The process of claim 25 in which the p-type layer is etched with a chemical etch.
References Cited (Backward Citations)
US4194954A
Cited
US4351706A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1986-11-07 | 1987-05-09 | 1987-11-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1990-11-07 | 1991-05-09 | 1991-11-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1994-11-07 | 1995-05-09 | 1995-11-08 | $7700.00 | Window Closed / Lapsed |