FABRICATION OF IN-PLANE-GATE TRANSISTOR STRUCTURES BY FOCUSED LASER BEAM-INDUCED ZN DOPING OF MODULATION-DOPED GAAS ALGAAS QUANTUM-WELLS/

Local Zn doping of n-modulation-doped GaAs/AlGaAs quantum well samples induced by absorption of a focused laser beam has been used to fabric ate in-plane-gate transistor structures. Laser-induced thermal Zn diff usion from a highly doped SiO2 emulsion into the sample surface layers allows direct writing of lateral npn structures with sub-mu m resolut ion. The p-doped lines form lateral potential barriers which are effic iently isolating the gate electrodes for large applied voltages at roo m temperature. Transistor structures with a 3-mu m-wide electron chann el in between V-shaped gates yield a transconductance of about 50 mu S and are pinched-off at gate voltages U-G less than or equal to-2.0 V.