Thin-film opto-electronic device and a method of making it

• US 20040087056A1
• Filed: 08/19/2003
• Published: 05/06/2004
• Est. Priority Date: 07/03/1998
• Status: Active Grant

• Current Assignee: Jef Poortmans, Johan Nijs, Khalid Said, Lieven Stalmans, Matty Caymax
• Original Assignee: Jef Poortmans, Johan Nijs, Khalid Said, Lieven Stalmans, Matty Caymax
• Inventors: Poortmans, Jef, Caymax, Matty, Stalmans, Lieven, Said, Khalid, Nijs, Johan
• Granted Patent: US 6,815,247 B2
• Time in Patent Office: Days
• US Class Current: 438/93
• CPC Class Codes: H01L 31/028 including, apart from doping material or other impurities, only elements of Group IV of the Periodic Table
• CPC Class Codes: H01L 31/0547 comprising light concentrating means of the reflecting type, e.g. parabolic mirrors, concentrators using total internal reflection
• CPC Class Codes: H01L 31/056 the light-reflecting means being of the back surface reflector [BSR] type
• CPC Class Codes: H01L 31/068 the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
• CPC Class Codes: H01L 31/072 the potential barriers being only of the PN heterojunction type
• CPC Class Codes: H01L 31/1804 comprising only elements of Group IV of the Periodic Table
• CPC Class Codes: Y02E 10/52 PV systems with concentrators
• CPC Class Codes: Y02E 10/547 Monocrystalline silicon PV cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

A thin-film opto-electronic device on a conductive silicon-containing substrate includes a sequence of layers. The layers include a layer of a porous medium preferably a porous silicon, on a substrate. The porous layer has both light diffusing and light reflecting properties. In addition, a non-porous layer is located on said porous silicon layer, with at least one first region and at least one second region being in said non-porous layer. The first region is of a first conductivity type acting as a light absorber and the second region has a conductivity of a second type, different from said first conductivity type. The sequence of layers is such that optical confinement is realised in the device.

Claims

1. A method for fabricating a thin-film opto-electronic device on a conductive silicon-containing substrate comprising the steps of growing a sequence of layers including at least the steps of:

a) forming a porous silicon layer on said substrate such that said porous silicon layer acts as a light diffuser and as a light reflector;

b) growing a non-porous layer on said porous silicon layer, said non-porous layer comprising at least one first region and at least one second region being formed in said non-porous layer, said first region of a first conductivity type, said second region of a second conductivity type, different from said first conductivity type,

and said sequence of layers being such that optical confinement is realised in said device.

2. A method as recited in claim 1, wherein said first region of a first conductivity type is acting as a light absorber.

3. A method as recited in claim 1, wherein said non-porous layer is a silicon-containing semiconductor layer, preferably a non-porous group IV and/or elemental and/or crystalline layer.

4. A method as recited in claim 3, wherein said non-porous layer is a Si or a SiGe or a Ge layer being grown by means of chemical vapour deposition or physical vapour or molecular beam epitaxy.

5. A method as recited in claim 1, wherein said porous silicon layer is formed by exposing the substrate to an electrochemical treatment or a chemical treatment or spark erosion.

6. A method as recited in claim 1, wherein said porous silicon layer has a thickness in the range from 0.1 μ

m to 1 μ

m and a porosity in the range from 20% to 70%.

7. A method as recited in claim 1, wherein the porous silicon layer formed comprises porous silicon parts and columnar conductive parts, said columnar conductive parts forming conductive connections between the substrate and the first region of the semiconductor layer;

said substrate and said first region having the same conductivity type.

8. A method as recited in claim 7, wherein prior to the formation of the porous silicon layer a patterned mask layer is formed on the substrate to thereby define at least one first area and at least one second area in the substrate, said first area being uncovered, said second area being covered with said mask layer;

thereafter said porous silicon layer is formed on said first area and said mask layer is removed from said second area;

thereafter a semiconductor layer is grown on said second area and on said porous silicon layer thereby creating said columnar conductive parts.

9. A method as recited in claim 1, wherein at least one third region is formed in said first region for contacting said first region, said third region being isolated from said second region and having the same conductivity type as said first region.