USRE33671E — Method of making high mobility multilayered heter…

Claim 1

Independent Claim 112 words

A method of enhancing the mobility of a narrow bandgap semiconductor material comprising the steps of: (a) forming said narrow bandgap material is a first plurality of spaced apart, narrow bandgap semiconductor layers, (b) forming a second plurality of wide bandgap semiconductor layers interleaved with and contiguous with said first plurality, and (c) forming said wide bandgap layers from a material which (i) is substantially lattice-matched to that of said narrow bandgap layers (ii) forms a conductor or valence band step at the interfaces with said narrow bandgap layers of sufficient magnitude to confine carriers, and (iii) is doped such that the impurity-concentration-thickness product thereof exceeds that of said narrow bandgap layers.

Claim 2

Independent Claim 112 words

A method of enhancing the mobility of a narrow bandgap semiconductor material comprising the steps of: (a) forming said narrow bandgap material is a first plurality of spaced apart, narrow bandgap semiconductor layers, (b) forming a second plurality of wide bandgap semiconductor layers interleaved with and contiguous with said first plurality, and (c) forming said wide bandgap layers from a material which (i) is substantially lattice-matched to that of said narrow bandgap layers (ii) forms a conductor or valence band step at the interfaces with said narrow bandgap layers of sufficient magnitude to confine carriers, and (iii) is doped such that the impurity-concentration-thickness product thereof exceeds that of said narrow bandgap layers.

Claim 3

Dependent Claim 38 words

The method of claim 1 wherein said forming steps include growing said layers by molecular beam epitaxy in an ultra high vacuum chamber wherein said first and second pluralities of layers are grown alternately on a semiconductor substrate.

Claim 4

Dependent Claim 60 words

The method of claim 2 wherein said chamber includes an oven carrying a dopant source which is used to generate a donor beam for doping said wide bandgap layers n-type and which is shuttered closed during the growth of said narrow bandgap layers so that impurities are incorporated in said narrow bandgap layers primarily from background contamination in said chamber.

Claim 5

Dependent Claim 66 words

The method of claim 3 wherein said forming step (a) is effective to grow said first plurality of .[.GaSa.]. .Iadd.GaAs .Iaddend.layers having an impurity concentration of about 10 14 or less, and said forming steps (b) and (c) are effective to grow said second plurality of n-type Al x Ga 1-x As layers 0.02≅x having a donor concentration of at least 10 16 /cm 3 .

Claim 6

Dependent Claim 47 words

The method of claim 1 wherein said forming steps (b) and (c) are effective to dope only a central portion of each of said wide bandgap layers with donors, thereby leaving a thin, undoped buffer zone in said wide bandgap layers adjacent said narrow bandgap layers. .Iadd.

Claim 7

Independent Claim 179 words

A method of enhancing the mobility of a narrow bandgap semiconductor material comprising the steps of: (a) forming said narrow bandgap material as a narrow bandgap first layer, (b) forming an essentially undoped wide bandgap semiconductor second layer contiguous with one side of said first layer, (c) forming a wide bandgap semiconductor third layer contiguous with said second layer, (d) forming an essentially undoped wide bandgap semiconductor fourth layer contiguous with the other side of said first layer, (e) forming a wide bandgap semiconductor fifth layer contiguous with said fourth layer, (f) forming said layers from materials which (i) form a conduction or valence band step at the interfaces with said first layer of sufficient magnitude to confine carriers, and (ii) are doped such that the impurity-concentration thickness product at least one of of said third layer and said fifth layer exceeds that of said first layer, and (g) forming electrode means electrically coupled to said layers and capable of causing said carriers to flow in said first layer in a direction essentially parallel to said interfaces. .Iaddend. .Iadd.

Claim 8

Independent Claim 179 words

A method of enhancing the mobility of a narrow bandgap semiconductor material comprising the steps of: (a) forming said narrow bandgap material as a narrow bandgap first layer, (b) forming an essentially undoped wide bandgap semiconductor second layer contiguous with one side of said first layer, (c) forming a wide bandgap semiconductor third layer contiguous with said second layer, (d) forming an essentially undoped wide bandgap semiconductor fourth layer contiguous with the other side of said first layer, (e) forming a wide bandgap semiconductor fifth layer contiguous with said fourth layer, (f) forming said layers from materials which (i) form a conduction or valence band step at the interfaces with said first layer of sufficient magnitude to confine carriers, and (ii) are doped such that the impurity-concentration thickness product at least one of of said third layer and said fifth layer exceeds that of said first layer, and (g) forming electrode means electrically coupled to said layers and capable of causing said carriers to flow in said first layer in a direction essentially parallel to said interfaces. .Iaddend. .Iadd.

Claim 9

Independent Claim 148 words

A method of fabricating a field effect transistor comprising the steps of: (a) forming a narrow bandgap semiconductor first layer which includes the channel of said transistor, (b) forming a wide bandgap semiconductor second layer on one side of said first layer, (c) forming a wide bandgap semiconductor third layer on the other side of said first layer, (d) forming said layers from materials which (i) form a conduction or valence band step at the interfaces with said first layer of sufficient magnitude to confine carriers, and (ii) are doped such that the impurity-concentration thickness product of at least one of said second and third layers exceeds that of said first layer, and (e) forming electrode means on said transistor including source and drain electrode means which are electrically coupled to said channel and gate electrode means for controlling the flow of carriers in said channel. .Iaddend. .Iadd.

Claim 10

Independent Claim 148 words

A method of fabricating a field effect transistor comprising the steps of: (a) forming a narrow bandgap semiconductor first layer which includes the channel of said transistor, (b) forming a wide bandgap semiconductor second layer on one side of said first layer, (c) forming a wide bandgap semiconductor third layer on the other side of said first layer, (d) forming said layers from materials which (i) form a conduction or valence band step at the interfaces with said first layer of sufficient magnitude to confine carriers, and (ii) are doped such that the impurity-concentration thickness product of at least one of said second and third layers exceeds that of said first layer, and (e) forming electrode means on said transistor including source and drain electrode means which are electrically coupled to said channel and gate electrode means for controlling the flow of carriers in said channel. .Iaddend. .Iadd.

Claim 11

Dependent Claim 49 words

The method of claim 7 wherein said forming steps (a), (b), (c) and (d) are effective to dope only a portion of the doped ones of said second and third layers, thereby leaving thin undoped buffer zones in said second and third layers adjacent to said first layer. .Iaddend.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1994-08-19	1995-02-18	1995-08-20	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1998-08-19	1999-02-18	1999-08-20	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2002-08-19	2003-02-18	2003-08-20	$7700.00	Window Closed / Lapsed

Method of making high mobility multilayered heterojunction device employing modulated doping

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