Abstract: A compound field effect transistor having multiple pinch-off voltages, comprising first and second field effect transistors, each field effect transistor comprising a semiconductor layer, the semiconductor layer having an electrically conducting layer therein. An ohmic contact layer on the semiconductor layer, a source and a drain on the ohmic contact layer, at least one gate on the semiconductor layer between source and drain, at least one gate of the first transistor and one gate of the second transistor being matched gates, each gate having the same effective thickness of electrically conducting layer beneath it, but the gates having different gate lengths.

Abstract: A heterojunction bipolar transistor comprising a substrate; a collector on the substrate; a base layer on the collector; an emitter layer on the base layer; the emitter layer comprising an upper emitter layer and a lower emitter layer between the upper emitter layer and base; the collector, base and emitter layers being npn or pnp doped respectively; characterized in that the lower emitter layer has a larger bandgap than the base layer and is AlxIn1-xP or GaxAl1-xP, x being in the range 0+ to 1.

Abstract: A compound field effect transistor having multiple pinch-off voltages, comprising first and second field effect transistors, each field effect transistor comprising a semiconductor layer, the semiconductor layer having an electrically conducting layer therein. An ohmic contact layer on the semiconductor layer, a source and a drain on the ohmic contact layer, at least one gate on the semiconductor layer between source and drain, at least one gate of the first transistor and one gate of the second transistor being matched gates, each gate having the same effective thickness of electrically conducting layer beneath it, but the gates having different gate lengths.

Abstract: A compound field effect transistor having multiple pinch-off voltages comprising: first and second field effect transistors, each field effect transistor comprising a semiconductor layer, the semiconductor layer having an electrically conducting layer therein; an ohmic contact layer on the semiconductor layer; a source and a drain on the ohmic contact layer; at least one gate on the semiconductor layer between source and drain; at least one gate of the first transistor and one gate of the second transistor being matched gates, each gate having the same effective thickness of electrically conducting layer beneath it but the gates having different gate lengths.

Abstract: A III-V field effect transistor comprising a semiconductor channel layer having an electrically conducting channel; an ohmic contact layer on the semiconductor channel layer, the ohmic contact layer having a recess structure disposed therethrough to the semiconductor channel layer; the bottom of the ohmic contact layer comprising an etch stop layer comprising Aluminium and Phosphorous and defining the shape of the recess at its junction with the semiconductor channel layer.

Abstract: A III-V field effect transistor comprising a semiconductor channel layer having an electrically conducting channel; an ohmic contact layer on the semiconductor channel layer, the ohmic contact layer having a recess structure disposed therethrough to the semiconductor channel layer; the bottom of the ohmic contact layer comprising an etch stop layer comprising Aluminium and Phosphorous and defining the shape of the recess at its junction with the semiconductor channel layer.

Abstract: A III-V field effect transistor includes a semiconductor channel layer having an electrically conducting channel and an ohmic contact layer on the semiconductor channel layer. The ohmic contact layer has a recess structure disposed therethrough to the semiconductor channel layer. The bottom of the ohmic contact layer includes an etch stop layer including Aluminum and Phosphorous and defining the shape of the recess at its junction with the semiconductor channel layer.

Abstract: A heterojunction bipolar transistor comprising a substrate; a collector on the substrate; a base layer on the collector; an emitter layer on the base layer; the emitter layer comprising an upper emitter layer and a lower emitter layer between the upper emitter layer and base; the collector, base and emitter layers being npn or pnp doped respectively; characterised in that the lower emitter layer has a larger bandgap than the base layer and is AlxIn1-xP or GaxAl1-xP, x being in the range 0+ to 1.

Abstract: A III-V field effect transistor comprising a semiconductor channel layer having an electrically conducting channel; an ohmic contact layer on the semiconductor channel layer, the ohmic contact layer having a recess structure disposed therethrough to the semiconductor channel layer; the bottom of the ohmic contact layer comprising an etch stop layer comprising Aluminium and Phosphorous and defining the shape of the recess at its junction with the semiconductor channel layer.