Heterojunction field effect transistor

Claim 2

A heterojunction field effect transistor comprising: a channel layer and a carrier supplying layer separated by a spacer layer; the carrier supplying layer having a charge carrier density with a minimum deep level density for creating a two-dimensional electron gas in the channel layer; the channel layer having the largest electron affinity among the three layers constituting the heterojunction FET; and the spacer layer interposed between the carrier supplying layer and the channel layer and comprising means for reducing Coulomb interaction between two-dimensional carriers in the channel layer and ions in the carrier supplying layer, the spacer layer comprising a material which increases the effective conduction band discontinuity ΔE c between the carrier supplying layer and the channel layer, the spacer layer having a graded band gap from substantially zero percent aluminum concentration at the junction with the carrier supplying layer to the maximum proportion x of aluminum concentration at the junction with the channel layer.

Claim 3

A heterojunction field effect transistor comprising: a channel layer and a carrier supplying layer separated by a spacer layer; the carrier supplying layer having a charge carrier density with a minimum deep level density for creating a two-dimensional electron gas in the channel layer; the channel layer having the largest electron affinity among the three layers constituting the heterojunction FET; the spacer layer interposed between the carrier supplying layer and the channel layer and comprising means for reducing Coulomb interaction between two-dimensional carriers in the channel layer and ions in the carrier supplying layer, the spacer layer comprising a material which increases the effective conduction band discontinuity ΔE c between the carrier supplying layer and the channel layer; the channel layer comprising non-doped In y Ga 1-x As, the spacer layer comprising non-doped Al x Ga 1-x As and the carrier supplying layer comprising n-type GaAs; and the spacer layer having a graded band gap from substantially zero percent aluminum concentration at the junction with the carrier supplying layer to the maximum proportion x of aluminum concentration at the junction with the channel layer.

Claim 4

A heterojunction field effect transistor comprising: a channel layer and a carrier supplying layer separated by a spacer layer; the carrier supplying layer having a charge carrier density with a minimum deep level density for creating a two-dimensional electron gas in the channel layer; the channel layer having the largest electron affinity among the three layers constituting the heterojunction FET; the spacer layer interposed between the carrier supplying layer and the channel layer and comprising means for reducing Coulomb interaction between two-dimensional carriers in the channel layer and ions in the carrier supplying layer, the spacer layer comprising a material which increases the effective conduction band discontinuity ΔE c between the carrier supplying layer and the channel layer; the channel layer comprising non-doped In y Ga 1-x As, the spacer layer comprising non-doped Al x Ga 1-x As and the carrier supplying layer comprising n-type GaAs; and the spacer layer having a graded band gap from substantially zero percent aluminum concentration at the junction with the carrier supplying layer to the maximum proportion x of aluminum concentration at the junction with the channel layer.

Claim 5

A heterojunction field effect transistor comprising: an In y Ga 1-y As channel layer and a GaAs carrier supplying layer separated by a spacer layer of Al x Ga 1-x As; the GaAs carrier supplying layer having a charge carrier density with a minimum deep level density for creating a two-dimensional electron gas in the channel layer; the In y Ga 1-y As channel layer having the largest electron affinity among the three layers; and the Al x Ga 1-x As spacer layer being interposed between the carrier layer and the channel layer and having a thickness sufficient for reducing Coulomb interaction between two-dimensional carriers in the channel layer and ions in the carrier supplying layer, the Al x Ga 1-x As spacer layer comprising a material which increases the effective conduction band discontinuity ΔE C between the carrier supplying layer and the channel layer, the spacer layer having a graded band gap from substantially zero percent aluminum concentration at the junction with the carrier supplying layer to the maximum percentage x of aluminum concentration at the junction with the channel layer.

Claim 6

A heterojunction field effect transistor comprising: an In y Ga 1-y As channel layer and a GaAs carrier supplying layer separated by a spacer layer of Al x Ga 1-x As; the GaAs carrier supplying layer having a charge carrier density with a minimum deep level density for creating a two-dimensional electron gas in the channel layer; the In y Ga 1-y As channel layer having the largest electron affinity among the three layers; and the Al x Ga 1-x As spacer layer being interposed between the carrier layer and the channel layer and having a thickness sufficient for reducing Coulomb interaction between two-dimensional carriers in the channel layer and ions in the carrier supplying layer, the Al x Ga 1-x As spacer layer comprising a material which increases the effective conduction band discontinuity ΔE C between the carrier supplying layer and the channel layer, the spacer layer having a graded band gap from substantially zero percent aluminum concentration at the junction with the carrier supplying layer to the maximum percentage x of aluminum concentration at the junction with the channel layer.