Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
126 words
A field effect transistor comprising: an epitaxially grown n-type GaInAs channel layer (4); first and second undoped GaInAs layers (3, 5) formed to sandwich said channel layer (4); a buffer layer (2) formed by a semiconductor having a band gap higher than that of said first layer (3) to be lattice-matched with said first layer (3) and to be in contact with one side of said first layer (3); a cap layer (6) formed by a semiconductor having a band gap higher than that of said second layer (5) to be lattice-matched with said second layer (5) and to be in contact with one side of said second layer (5); and a gate electrode (7) formed to be in Schottky contact with said cap layer (6).
Claim 2
Dependent Claim
55 words
A transistor according to claim 1, wherein each of said first and second layers (3, 5) is a graded layer in which an In composition ratio is gradually varied such that an In composition ratio is high on said channel layer side and is low on said buffer layer side and said cap layer side.
Claim 3
Dependent Claim
48 words
A transistor according to claim 1 or 2, wherein In composition ratios of said first and second layers (3, 5) are equal to an In composition ratio of said channel layer (4) on junction surfaces between said channel layer (4) and said first and second layers (3, 5).
Claim 4
Dependent Claim
35 words
A transistor according to claim 1, wherein said buffer layer (2) is formed on a semi-insulating substrate (1), said semi-insulating substrate being preferably made of GaAs and said buffer layer being preferably made of GaAs.
Claim 5
Dependent Claim
28 words
A transistor according to any of the proceding claims, wherein said cap layer (6) is made of one member selected from the group consisting of GaAs and AlGaAs.
Claim 6
Dependent Claim
90 words
A transistor according to claim 1, wherein said buffer layer (2) is made of GaAs, said first layer (3) is a graded layer in which an In composition ratio is gradually varied such that an In composition ratio is high on said channel layer side and is low on said buffer layer side, and an In composition ratio of said first layer (3) is substantially equal to an In composition ratio of said buffer layer (2) on a junction surface between said buffer layer (2) and said first layer (3).
Claim 7
Dependent Claim
100 words
A transistor according to claim 1, wherein said cap layer (6) is made of one member selected from the group consisting of GaAs and AlGaAs, said second layer (5) is a graded layer in which an In composition ratio is gradually varied such that an In composition ratio is high on said channel layer side and is low on said cap layer side, and an In composition ratio of said second layer (5) is substantially equal to an In composition ratio of said cap layer (6) on a junction surface between said cap layer (6) and said second layer (5).
Claim 8
Dependent Claim
27 words
A transistor according to claim 1, wherein each of said first and second layers (3, 5) is a uniform layer having a substantially constant In composition ratio.
Claim 9
Dependent Claim
32 words
A transistor according to claim 8, wherein the In composition ratios of said first and second layers (3, 5) are substantially equal to an In composition ratio of said channel layer (4).
Claim 10
Dependent Claim
44 words
A transistor according to claim 9, wherein a total film thickness of three layers constituted by said first layer (3), said channel layer (4) and said second layer (5) is smaller than a critical film thickness at which dislocation is caused by lattice distortion.
Claim 11
Dependent Claim
90 words
A transistor according to claim 1, wherein said buffer layer (2) is made of GaAs, said cap layer (6) is made of one member selected from the group consisting of GaAs and AlGaAs, said first and second layers (3, 5) are made of undoped Ga 0.85 In 0.15 As, said channel layer (4) is made of Ga 0.85 In 0.15 As doped with an n-type impurity, and a total film thickness of three layers constituted by said first layer, said channel layer and said second layer is about 150 Å.
Claim 12
Dependent Claim
60 words
A transistor according to claim 1, wherein, when the sum of a Ga composition ratio and an In composition ratio is set to be 1, an In composition ratio of GaInAs for forming said channel layer (4) is not less than 0.1 and not more than 0.3, said channel layer (4) being preferably made of Ga 0.85 In 0.15 As.
Claim 13
Dependent Claim
31 words
A transistor according to any of the proceding claims, further comprising a source electrode (8) and a drain electrode (9) formed to be in ohmic contact with said cap layer (6).
Claim 14
Dependent Claim
62 words
A transistor according to any of claims 1 to 12, wherein contact layers (11) are formed on said cap layer (6), and a source electrode (8) and a drain electrode (9) are formed on said contact layers (11), said contact layers being preferably made of one member selected from the group consisting of GaAs doped with Si and GaInAs doped with Si.