A QUANTUM-WELL DELTA-DOPED GAAS-FET FABRICATED BY LOW-PRESSURE METAL ORGANIC-CHEMICAL VAPOR-DEPOSITION

A quantum well delta-doped n-type GaAs layer with Ga source open has been grown successfully by the low-pressure metal organic chemical vapor deposition (LP-MOCVD). The measured capacitance-voltage profile shows that a sheet-doping concentration up to 5 x 10(12) cm-2 for the delta-doped GaAs layer can be easily achieved. The full-width at half-maximum (FWHM) is quite narrow. From the Hall measurement, the electron mobility increases inversely proportional to the delta-doping concentration. An enhanced mobiity can be obtained more than 2300 and 4300 cm2/Vs with doping concentration of 5.0 x 10(18) cm-3 at 300 and 77 K, respectively. Based on this technique, a quantum well delta-doped GaAs FET has been fabricated and demonstrated. With a gate geometry of 5 x 250-mu-m2 and doping concentration of 5.9 x 10(18) cm-3, the estimated transconductance of the delta-doped FET is 64 mS/mm. Since there is an undoped GaAs layer grown on the top of the delta-doped sheet, the breakdown voltage can be increased significantly (> 17 V). Furthermore, the saturation current density can be obtained higher than 110 mA/mm.