Claims
- 1. An EMI shield for shielding EMI radiations of a known frequency comprising:
- (a) a bulk semiconductor material of uniform composition having first and second spaced apart surface regions,
- (b) said bulk semiconductor material being doped with a dopant with progressively increasing dopant concentration in a direction from said first to said second surface regions,
- (c) said doped semiconductor material having an interface intermediate said first and second surface regions,
- (d) said doped semiconductor material having an interface intermediate said first and second surface regions said doped semiconductor material demonstrating an abrupt change from relatively highly electrically conductive on one side of said interface to relatively highly electrically insulative on the opposing side of said interface in the region of said bulk semiconductor material immediately adjacent said interface,
- (e) the thickness of the electrically insulative side of said bulk semiconductor material being one quarter of a wave length of said known frequency.
- 2. The shield of claim 1 wherein said bulk semiconductor material is taken from the class consisting of GaAs and GaP.
- 3. The shield of claim 2 wherein said dopant is taken from the class consisting of Se, Te and S.
- 4. The shield of claim 1 wherein the ratio of the resistivity of said portion of said bulk semiconductor material immediately adjacent one side of said interface to the portion of said bulk semiconductor material immediately adjacent the other side of said interface is at least about 1:10.sup.7.
- 5. The shield of claim 2 wherein the ratio of the resistivity of said portion of said bulk semiconductor material immediately adjacent one side of said interface to the portion of said bulk semiconductor material immediately adjacent the other side of said interface is at least about 1:10.sup.7.
- 6. The shield of claim 3 wherein the ratio of the resistivity of said portion of said bulk semiconductor material immediately adjacent one side of said interface to the portion of said bulk semiconductor material immediately adjacent the other side of said interface is at least about 1:10.sup.7.
- 7. The shield of claim 4 wherein said abrupt change takes place over a distance of less than one millimeter.
- 8. The shield of claim 5 wherein said abrupt change takes place over a distance of less than one millimeter.
- 9. The shield of claim 6 wherein said abrupt change takes place over a distance of less than one millimeter.
CROSS REFERENCE TO PRIOR APPLICATIONS
This is a continuation of application Ser. No. 7/977,388 filed Nov. 17, 1992 and a continuation-in-part of Ser. No. 07/748,602, filed Aug. 22, 1991, the contents of which are incorporated herein by reference now abandoned.
US Referenced Citations (5)
Number |
Name |
Date |
Kind |
3496118 |
Willardson et al. |
Feb 1970 |
|
4778731 |
Kraatz et al. |
Oct 1988 |
|
4826266 |
Baird et al. |
May 1989 |
|
4939043 |
Birick et al. |
Jul 1990 |
|
5173443 |
Biricik et al. |
Dec 1992 |
|
Non-Patent Literature Citations (1)
Entry |
Chang et al., "Radial Segration Induced by Natural Convection and Melt/Solid Interface Shape in Vertical Bridgman Growth", Journal of Crystal Growth, vol. 63 pp. 343-364, 1983. |
Continuations (1)
|
Number |
Date |
Country |
Parent |
977388 |
Nov 1992 |
|
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
748602 |
Aug 1991 |
|