SILICON DELTA-DOPED ALGAAS BY LOW-PRESSURE METALORGANIC VAPOR-PHASE EPITAXY

Delta doping of Si in Al0.22Ga0.78As by low pressure metalorganic vapor phase epitaxy has been explored for growth interruption times ranging from 10 to 60 s and for varying SiH4 partial pressures of 7.8 x 10(-4) and 1.2 x 10(-3) mbar. The resultant sheet concentrations were linear with both time and SiH4 content up to saturation at 3.6 x 10(12) cm(-2). The full width at half maximum versus sheet concentration was found to correspond to theoretical predictions, indicating the absence of diffusion, with a minimum value of 60 Angstrom for a sheet concentration of 3.6 x 10(12) cm(-2). For Si doses higher than 1 x 10(-2) ml SiH4, an increase in full width at half maximum (FWHM) was observed. Pseudomorphic high electron mobility transistor device results show a 300 K channel mobility of 3030 cm(2)/V.s with a sheet concentration of 2.7 x 10(12) cm(-2). The maximum extrinsic transconductance of such devices was 400 mS/mm with a corresponding saturation current of 360 mA/mm for 0.5 mu m gate length devices.