Transistor doped GaAs

A field-effect transistor has been prepared using a modulation doped GaAs/InQ 2GaQegAs SLS as the channel of the device (35). The device consisted of a p-type GaAs substrate, a p-type (4 x 10- 8 cm J), 1 pm InQ.jGaQ.gAs bufffer, an n-type (1 x 101 cm J),... 

H. Morkoc and H. Vnlu, Factors Affecting the Performance of (Al, Ga)As/GaAs and (Al, Ga)As/InGaAs Modulation-Doped Field-Effect Transistors Microwave and Digital Applications... 

The heavily -doped AlGaAs donates the electrons that are forced into the semi-insulating (near intrinsic) GaAs to form an n-channel depletion FET. Since the ionized donors stay in the AlGaAs layer, they do not scatter the electrons in the n-channel which permits the conducting electron to have very high mobilities. The high electron mobility allows the transistor to operate at frequencies in excess of 300 GHz. 

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