Navid S Fatemi

US Patent:

7339109, Mar 4, 2008

Filed:

Jun 19, 2001

Appl. No.:

09/885319

Inventors:

Mark A. Stan - Albuquerque NM, US
Nein Y. Li - Sunnyvale CA, US
Frank A. Spadafora - Baden PA, US
Hong Q. Hou - Albuquerque NM, US
Paul R. Sharps - Albuquerque NM, US
Navid S. Fatemi - Albuquerque NM, US

Assignee:

Emcore Corporation - Albuquerque NM

International Classification:

H01L 31/0216
H01L 31/0256

US Classification:

136256, 136262

Abstract:

Apparatus and Method for Optimizing the Efficiency of Germanium Junctions in Multi-Junction Solar Cells. In a preferred embodiment, an indium gallium phosphide (InGaP) nucleation layer is disposed between the germanium (Ge) substrate and the overlying dual-junction epilayers for controlling the diffusion depth of the n-doping in the germanium junction. Specifically, by acting as a diffusion barrier to arsenic (As) contained in the overlying epilayers and as a source of n-type dopant for forming the germanium junction, the nucleation layer enables the growth time and temperature in the epilayer device process to be minimized without compromising the integrity of the dual-junction epilayer structure. This in turn allows the arsenic diffusion into the germanium substrate to be optimally controlled by varying the thickness of the nucleation layer. An active germanium junction formed in accordance with the present invention has a typical diffused junction depth that is ⅕ to of that achievable in prior art devices.

US Patent:

7553691, Jun 30, 2009

Filed:

Apr 26, 2005

Appl. No.:

11/114454

Inventors:

Navid Fatemi - Albuquerque NM, US
Daniel J. Aiken - Cedar Crest NM, US
Mark A. Stan - Albuquerque NM, US

Assignee:

Emcore Solar Power, Inc. - Albuquerque NM

International Classification:

H01L 21/00
H01L 25/00

US Classification:

438 94, 438 47, 438172, 438191, 438235, 257 51, 257 94, 257200, 257E33032, 257E33033, 136206, 136249, 136254, 136255, 136262

Abstract:

A method and a multijunction solar device having a high band gap heterojunction middle solar cell are disclosed. In one embodiment, a triple-junction solar device includes bottom, middle, and top cells. The bottom cell has a germanium (Ge) substrate and a buffer layer, wherein the buffer layer is disposed over the Ge substrate. The middle cell contains a heterojunction structure, which further includes an emitter layer and a base layer that are disposed over the bottom cell. The top cell contains an emitter layer and a base layer disposed over the middle cell.

US Patent:

7629240, Dec 8, 2009

Filed:

Jun 2, 2005

Appl. No.:

11/143516

Inventors:

Mark A. Stan - Albuquerque NM, US
Nein Y. Li - Sunnyvale CA, US
Frank A. Spadafora - Albuquerque NM, US
Hong Q. Hou - Albuquerque NM, US
Paul R. Sharps - Albuquerque NM, US
Navid S. Fatemi - Albuquerque NM, US

Assignee:

Emcore Solar Power, Inc. - Albuquerque NM

International Classification:

H01L 21/22

US Classification:

438542, 438558, 257E33028

Abstract:

Dopant diffusion into semiconductor material is controlled during fabrication of a semiconductor structure by depositing a nucleation layer over a first layer of the semiconductor structure and depositing a device layer containing the dopant over the nucleation layer. The nucleation layer serves as a diffusion barrier by limiting in depth the diffusion of the dopant into the first layer. The dopant can include arsenic (As).

US Patent:

7709287, May 4, 2010

Filed:

Apr 10, 2006

Appl. No.:

11/401720

Inventors:

Navid Fatemi - Albuquerque NM, US
Daniel J. Aiken - Cedar Crest NM, US
Mark A. Stan - Albuquerque NM, US

Assignee:

Emcore Solar Power, Inc. - Albuquerque NM

International Classification:

H01L 21/00
H01L 31/00
H01L 31/04

US Classification:

438 94, 438 74, 438 93, 438235, 438312, 257 12, 257 96, 257 97, 257E21101, 257E21102, 257E33032, 257E33033, 257E33034, 136249, 136256, 136261, 136262

Abstract:

A method of forming a multijunction solar cell includes providing a substrate, forming a first subcell by depositing a nucleation layer over the substrate and a buffer layer including gallium arsenide (GaAs) over the nucleation layer, forming a middle second subcell having a heterojunction base and emitter disposed over the first subcell and forming first and second tunnel junction layers between the first and second subcells. The first tunnel junction layer includes GaAs over the first subcell and the second tunnel junction layer includes aluminum gallium arsenide (AlGaAs) over the first tunnel junction layer. The method further includes forming a third subcell having a homojunction base and emitter disposed over the middle subcell.

US Patent:

20040084694, May 6, 2004

Filed:

Oct 31, 2002

Appl. No.:

10/285780

Inventors:

Navid Fatemi - Albuquerque NM, US
Daniel Aiken - Cedar Crest NM, US
Mark Stan - Albuquerque NM, US

International Classification:

H01L031/0336

US Classification:

257/200000

Abstract:

A method and a multijunction solar device having a high band gap heterojunction middle solar cell are disclosed. In one embodiment, a triple-junction solar device includes bottom, middle, and top cells. The bottom cell has a germanium (Ge) substrate and a buffer layer, wherein the buffer layer is disposed over the Ge substrate. The middle cell contains a heterojunction structure, which further includes an emitter layer and a base layer that are disposed over the bottom cell. The top cell contains an emitter layer and a base layer disposed over the middle cell.

US Patent:

20080149177, Jun 26, 2008

Filed:

Mar 3, 2008

Appl. No.:

12/041490

Inventors:

Mark A. Stan - Albuquerque NM, US
Nein Y. Li - Albuquerque NM, US
Frank A. Spadafora - Baden PA, US
Hong Q. Hou - Arcadia CA, US
Paul R. Sharps - Albuquerque NM, US
Navid S. Fatemi - Albuquerque NM, US

Assignee:

EMCORE CORPORATION - Albuquerque NM

International Classification:

H01L 31/06
H01L 31/0216

US Classification:

136262, 136255

Abstract:

Apparatus and Method for Optimizing the Efficiency of Germanium Junctions in Multi-Junction Solar Cells. In a preferred embodiment, an indium gallium phosphide (InGaP) nucleation layer is disposed between the germanium (Ge) substrate and the overlying dual-junction epilayers for controlling the diffusion depth of the n-doping in the germanium junction. Specifically, by acting as a diffusion barrier to arsenic (As) contained in the overlying epilayers and as a source of n-type dopant for forming the germanium junction, the nucleation layer enables the growth time and temperature in the epilayer device process to be minimized without compromising the integrity of the dual-junction epilayer structure. This in turn allows the arsenic diffusion into the germanium substrate to be optimally controlled by varying the thickness of the nucleation layer. An active germanium junction formed in accordance with the present invention has a typical diffused junction depth that is ⅕ to of that achievable in prior art devices. Furthermore, triple-junction solar cells incorporating a shallow n-p germanium junction of the present invention can attain 1 sun AMO efficiencies in excess of 26%.

US Patent:

20100240171, Sep 23, 2010

Filed:

Apr 8, 2010

Appl. No.:

12/756799

Inventors:

Mark A. Stan - Albuquerque NM, US
Nein Y. Li - Albuquerque NM, US
Frank A. Spadafora - Baden PA, US
Hong Q. Hou - Arcadia CA, US
Paul R. Sharps - Albuquerque NM, US
Navid S. Fatemi - Albuquerque NM, US

Assignee:

Emcore Solar Power, Inc. - Albuquerque NM

International Classification:

H01L 31/18
H01L 21/22

US Classification:

438 87, 438 93, 257E21135, 257E31005

Abstract:

A multijunction solar cell is fabricated according to an embodiment by providing a substrate, depositing a nucleation first layer over and directly in contact with the substrate, depositing a second layer containing an arsenic dopant over the nucleation layer and depositing a sequence of layers over the second layer forming at least one solar subcell. The nucleation layer serves as a diffusion barrier to the arsenic dopant such that diffusion of the arsenic dopant into the substrate is limited in depth by the nucleation layer.

US Patent:

52948340, Mar 15, 1994

Filed:

Jun 1, 1992

Appl. No.:

7/891797

Inventors:

Navid S. Fatemi - University Heights OH
Victor G. Weizer - Cleveland Heights OH

Assignee:

Sverdrup Technology, Inc. - Tullahoma TN

International Classification:

H01L 2348

US Classification:

257745

Abstract:

A method of enhancing the specific contact resistivity in InP semiconductor devices and improved devices produced thereby are disclosed. Low resistivity values are obtained by using gold ohmic contacts that contain small amounts of gallium or indium and by depositing a thin gold phosphide interlayer between the surface of the InP device and the ohmic contact. When both the thin interlayer and the gold-gallium or gold-indium contact metallizations are used, ultra low specific contact resistivities are achieved. Thermal stability with good contact resistivity is achieved by depositing a layer of refractory metal over the gold phosphide interlayer.