different from the first material is formed over the buffer layer the second layer has a total thickness less than 250 u00e5 a doped third semiconductor layer formed over the second layer the net has a dopant concentration in the second layer is greater than the net dopant concentration in the third layer a gate layer is positioned over the third layer in a preferred embodiment the second layer is a pulse doped pseudeomorphic material there is also provided a method for making the heterostructure field effect transistor a doped pseudomorphic semiconductor layer of a first conductivity type is formed between first and second other semiconductor layers the second layer including a net dopant concentration of the first conductivity type a schottky gate electrode is formed in contact with the second layer application_number US 61800590 A description although the performance of gaas mesfets has been improved significantly by using extremely heavily doped active layers it is now apparent that further improvement can be obtained by forming a heterostructure device which does not operate as a hemt fig1 is a schematic cross sectional elevation view of a first preferred embodiment heterostructure device generally denoted by reference numeral 10 according to the present invention the device 10 includes a semi insulating gaas substrate 12 a 1 u03bcm thick undoped gaas buffer layer 13 a thin 150 u00e5 and heavily doped in x ga sub 1 x as layer 14 an n type gaas layer 16 doped to approximately 10 17 cm 3 a second n type gaas layer 18 doped to approximately 10 18 cm 3 a 0 25 u03bcm.