High electron mobility semiconductor device employing selectively doped heterojunction

Claim 2

High electron mobility semiconductor device comprising : - a channel layer (12) made from undoped gallium arsenide (i-GaAs) layer; - a first spacer layer(13) made from undoped aluminum gallium arsenide (i-Al x-1 As) fabricated contiguous to said channel layer and forming an heterojunction therewith; and - an n-type aluminum gallium arsenide (n-AlxGal-xAs) layer (15); said device being characterized in that it further comprises : a second spacer layer (14) made from undoped gallium arsenide (i-GaAs) and located between said first spacer layer (13) and said n-Al x Ga 1-x As layer (15) and contiguous thereto, said second spacer layer (14) having a thickness to prevent the diffusion of impurity from said n-type aluminum gallium arsenide layer (15) to said channel layer (12), and the total thickness of said first and second spacers (13,14) being such as to accumulate a two dimensional electron gas (2DEG) in said channel layer (12) close to said heterojunction.

Claim 3

A high electron mobility semiconductor device according to claim 1, characterized in that it comprises a substrate (11) made of high resistivity gallium arsenide, on which said channel layer (12) is fabricated contiguous to the substrate.

Claim 4

A high electron mobility semiconductor device according to any one of claims 1 or 2, characterized in that said total thickness of said first and second spacer layers (13,14) is less than 10x10 -9 m.

Claim 5

A high electron mobility semiconductor device according to any one of claims 1 to 3, characterized in that the thickness of said second spacer layer (14) is comprised between substantially 1.5x10 -9 and 3x10 -9 m.

Claim 6

A high electron mobility semiconductor device according to any one of claims 1 to 4, characterized in that the thickness of said first spacer layer (13) is comprised between substantially 2x10 -9 and 4x10 -9 m.

Claim 7

A high electron mobility semiconductor device according to any one of claims 1 to 5, characterized in that the aluminum composition x in the first Al x Ga 1-x As spacer layer (13) is substantially 0.3.

Claim 8

A high electron mobility semiconductor device according to any one of claims 1 to 6, characterized in that the aluminum composition x in the n-Al x Ga 1-x As layer (15) is substantially 0.3.

Claim 9

A high electron mobility semiconductor device according to any one of claims 1 to 7, characterized in that said n-type Al x Ga 1-x As layer (15) is doped with silicon.

Claim 10

A high electron mobility semiconductor device according to claim 8, characterized in that the dose of silicon is approximately 1 x 10 18 cm -3 .

Claim 11

A high electron mobility semiconductor device according to any one of claims 1 to 9, characterized in that the thickness of said channel layer (12) is approximately 0.5 µm.

Claim 12

A high electron mobility semiconductor device, characterized in that it comprises : a substrate (11) made of high resistivity GaAs; a channel layer (13) made of undoped gallium arsenide (i-GaAs) layer of approximately 0.5 pm thick; a first spacer layer (13) made from undoped aluminum gallium arsenide (i-Al x Ga 1-x As) having a thickness of approximately 4x10 -9 m and fabricated contiguous to said channel layer (12); a second spacer layer (14) made from undoped gallium arsenide (i-GaAs) having a thickness of approximately 2xlo -9 m and fabricated contiguous to said first spacer layer (13); a first n-type aluminum gallium arsenide (n-Al x Ga 1-x As) layer (15) having a thickness of approximately 60x10 -9 m fabricated contiguous to said second spacer layer (14); a second n-type gallium arsenide (n-GaAs) layer (16) having a thickness of approximately 50xlo -9 m fabricated contiguous to said first n-type aluminum gallium arsenide (n-Al x Ga 1-x As) layer (15); a recess fabricated in said second n-type gallium arsenide (n-GaAs) layer (16) to expose the first n-Al x Ga 1-x As layer (15); n-type regions (17) highly doped with selenium (Se)and reaching the channel region (12) from the surface of the second n-GaAs layer (16); a gate electrode (20) contacted to said first n-Al x Ga 1-x As layer (15) in said recess; and source and drain electrodes (18,19) respectively connected to said highly doped n-type regions (17).

Claim 13

A high electron mobility semiconductor device, characterized in that it comprises : a substrate (11) made of high resistivity GaAs; a channel layer (13) made of undoped gallium arsenide (i-GaAs) layer of approximately 0.5 pm thick; a first spacer layer (13) made from undoped aluminum gallium arsenide (i-Al x Ga 1-x As) having a thickness of approximately 4x10 -9 m and fabricated contiguous to said channel layer (12); a second spacer layer (14) made from undoped gallium arsenide (i-GaAs) having a thickness of approximately 2xlo -9 m and fabricated contiguous to said first spacer layer (13); a first n-type aluminum gallium arsenide (n-Al x Ga 1-x As) layer (15) having a thickness of approximately 60x10 -9 m fabricated contiguous to said second spacer layer (14); a second n-type gallium arsenide (n-GaAs) layer (16) having a thickness of approximately 50xlo -9 m fabricated contiguous to said first n-type aluminum gallium arsenide (n-Al x Ga 1-x As) layer (15); a recess fabricated in said second n-type gallium arsenide (n-GaAs) layer (16) to expose the first n-Al x Ga 1-x As layer (15); n-type regions (17) highly doped with selenium (Se)and reaching the channel region (12) from the surface of the second n-GaAs layer (16); a gate electrode (20) contacted to said first n-Al x Ga 1-x As layer (15) in said recess; and source and drain electrodes (18,19) respectively connected to said highly doped n-type regions (17).